Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops

*Ayman EL Sabagh, Akbar Hossain, Mohammad Sohidul Islam, Muhammad Aamir Iqbal, Ali Raza, Çetin Karademir, Emine Karademir, Abdul Rehman, Md Atikur Rahman, Rajesh Kumar Singhal, Analía Llanes, Muhammad Ali Raza, Muhammad Mubeen, Wajid Nasim, Celaleddin Barutçular, Ram Swaroop Meena and Hirofumi Saneoka*

#### **Abstract**

The rising concentration of atmospheric carbon dioxide (aCO2) and increasing temperature are the main reasons for climate change, which are significantly affecting crop production systems in this world. However, the elevated carbon dioxide (CO2) concentration can improve the growth and development of crop plants by increasing photosynthetic rate (higher availability of photoassimilates). The combined effects of elevated CO2 (eCO2) and temperature on crop growth and carbon metabolism are not adequately recognized, while both eCO2 and temperature triggered noteworthy changes in crop production. Therefore, to increase crop yields, it is important to identify the physiological mechanisms and genetic traits of crop plants which play a vital role in stress tolerance under the prevailing conditions. The eCO2 and temperature stress effects on physiological aspects as well as biochemical profile to characterize genotypes that differ in their response to stress conditions. The aim of this review is directed the open-top cavities to regulate the properties like physiological, biochemical, and yield of crops under increasing aCO2, and temperature. Overall, the extent of the effect of eCO2 and temperature response to biochemical components and antioxidants remains unclear, and therefore further studies are required to promote an unperturbed production system.

**Keywords:** elevated CO2, heat stress, physio-biochemical mechanisms

#### **1. Introduction**

Climate change in the form of increasing temperature and increasingly variable rainfall patterns threatens the production of the crop [1, 2]. Therefore, elevated CO2 (eCO2) absorption may indorse plant growth, whereas increased temperature

is repressive for C3 plants. Both CO2 and temperature caused significant changes in crop productivity. The collaborative properties of eCO2 and increased temperatures on the crop growth and carbon metabolism are not well known.

The fluctuating climatic surroundings are predictable to upsurge the atmospheric CO2 (aCO2) meditation, temperatures and modify the rainfall outline. The aCO2 meditation is prophesied to range 550 ppm by 2050, and possibly surpass 700 ppm by the end of the present century [3]. These fluctuations are expected to disturb the creation and output of cultivated crops, and stimulus the upcoming food safety. The influence analysis of climate alteration on worldwide food construction reveals a 0.5% failure by 2020 and 2.3% by 2050 [4]. The progress of climate arranged germplasm to counterbalance these wounded is of the highest reputation [5].

The eCO2 is significant abiotic stress and has a noteworthy fertilization encouragement on crops. Widespread preceding educations have described that eCO2 meaningfully enhanced the water use efficiency (WUE), reduced transpiration frequency, abridged maize growth rate, and augmented plant height, leaf number, leaf area, growth frequency, and overall yield [6]. Furthermore, the cumulative of aCO2 disturbs precipitation equilibrium, which can alter the periodic precipitation circulation [7]. It has been predicted that this result would carry about a 10% upsurge or decline in water capitals in several areas [8]. The raised temperature, i.e., heat stress (HS) damage growth and physiological ailments, and consequentially reduce yield [9]. Increased temperature due to eCO2 has a primary effect on the food grain invention reliant on the places. With the rising temperature by 1.0–2.0°C in tropical and subtropical states and the food grain manufacture in India is predictable to decline up to 30% [9].

The C4 grass maize (*Zea mays* L.) is the third most vital food crop worldwide in the relation of the invention, and its claim is prophesied to rise by 45% from 1997 to 2020 [10]. Educations with maize retort to dual the ambient CO2 presented variable possessions on growth fluctuating from no inspiration of yield [11] to 50% stimulation [12]. The growth and productivity of maize are expected to be pretentious by raised aCO2 and temperature. Raised temperature severely disturbs the growth, and yield of maize plants [13]. There is unpredictable information on the properties of eCO2 on the vintage of maize changing from slight positive consequence [14], no consequence [15] to rice harvest by 50% [16].

Record of the experimentations on the influences of eCO2 and temperature on the crop yield, though, used measured atmosphere amenities like phytotron and plant growth cavities or crop growth reproduction models [13, 17]. Determination of the impact of raised CO2 on the photosynthesis tolerance to severe HS is vital to expect the plant replies for universal warming since photosynthesis is sensitive to severe HS and aCO2 upsurges slightly [18, 19]. Further, flowering is a critical element for plant generative achievement and seed-set. The increase in temperature and eCO2 is the main climate revolution issues that might influence plant suitability and associated flowering actions. Resolving the influence of these ecological issues on the flowering actions like time of days to anthesis and flowering (duration from germination till flowering) is serious to appreciate the acclimatization of crops in altering climate [20].

#### **2. Interaction of eCO2 with high-temperature stress and other factors to climate change**

The impacts of eCO2 and stress factors on crops have been made using controlled atmosphere amenities like plant growth cavities or crop growth reproduction

**129**

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops*

models in many studies [13]. The eCO2 contributes to global warming, causing alterations in the precipitations, water scarcity and changes at temperatures in several regions affecting the growth and development of crop plants [3]. However, the interactive effects of eCO2 and environmental stress conditions on the crop growth and carbon metabolism are not well predictable. The interactions between eCO2 and stress factors are critical to photosynthesis performance. It has been reported how stomata react to eCO2 levels, but the effects on photosynthesis performance of other

Numerous studies showed the combining impacts of eCO2 and drought and revealed that the machines are different from singular eCO2 and drought. The impact of combined eCO2 and drought are varying with crop stage such as during vegetative stage, and it restricted the shoot development, decreased leaf area, diminished mobilization of nutrients due to weak root growth, reduced stomatal closure, transpiration, and relative water contents (RWC). However, it enhances the resource use efficiencies of the plant, including WUE, light use efficiency (LUE), and nutrient use efficiency (NUE) at a certain level [22, 23]. Similarly, eCO2 and drought affect reproductive growth severely such as the impacts on the pollen abortion, pollination, flower formation, panicle length, panicle weight, seed formation,

Altering climate, counting eCO2, increasing temperatures, changing precipitation designs have influenced terrestrial environment assembly and function, carbon and water balance, and finally production of crops [24, 25]. Several experiments have described the biological replies to CO2 enhancement and their communication with ecological alteration at different levels [26]. The temperature has an important role in plant growth and development and regulates the several functions and enzymatic reactions in plants. Although, the increased value of temperature causes several abnormalities in plants such as reduces the chlorophyll contents, leaf growth, fresh and dry biomass, photosynthesis, and stomata limitations, inhibits the functions of several temperature-sensitive enzymes such as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Impacts of eCO2 and temperature combined stresses are very destructive at the reproductive phase. They may cause reduced pollination, spike sterility, less filling of grain, reduction of grain size and number,

It has been reported that eCO2 promotes an initial stimulation of photosynthesis by an increase of substrate or RuBisCO carboxylation activity and selfconsciousness of RuBisCO oxygenation, which might ultimately underwrite for advanced biomass in cereal crops [27, 28]. Nevertheless, growth responses over the long-standing under eCO2 conditions include a reduction of photosynthesis measurements and several regulatory mechanisms to avoid potential damage by this condition. A regulatory mechanism to maintain the growth and expansion of plants consists of the equilibrium among manufacture and removal of reactive oxygen species (ROS) at the intracellular level. This balance is continued by both enzymatic

The enzymatic machinery involves numerous antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), guaiacol peroxidase (POX), peroxiredoxins (Prxs), and enzymes of the ascorbateglutathione (AsAGSH) cycle. The AsAGSH includes different enzymes like ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) [30, 32]. Modifications of this enzymatic antioxidant component have been reported in studies of cereal crops under eCO2 conditions with contradictory results. Thus, the response of these antioxidants components is unclear with studies that find to

*DOI: http://dx.doi.org/10.5772/intechopen.94128*

environmental factors are poorly understood [21].

test weight, and yield potential of major crops [22].

and non-enzymatic antioxidant defense systems [29–31].

increase [33], decreases [34], or no consistent alterations [35].

seed size and, yield potential of important agriculture crops [22].

#### *Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops DOI: http://dx.doi.org/10.5772/intechopen.94128*

*Abiotic Stress in Plants*

the highest reputation [5].

India is predictable to decline up to 30% [9].

consequence [15] to rice harvest by 50% [16].

is repressive for C3 plants. Both CO2 and temperature caused significant changes in crop productivity. The collaborative properties of eCO2 and increased temperatures

The fluctuating climatic surroundings are predictable to upsurge the atmospheric CO2 (aCO2) meditation, temperatures and modify the rainfall outline. The aCO2 meditation is prophesied to range 550 ppm by 2050, and possibly surpass 700 ppm by the end of the present century [3]. These fluctuations are expected to disturb the creation and output of cultivated crops, and stimulus the upcoming food safety. The influence analysis of climate alteration on worldwide food construction reveals a 0.5% failure by 2020 and 2.3% by 2050 [4]. The progress of climate arranged germplasm to counterbalance these wounded is of

The eCO2 is significant abiotic stress and has a noteworthy fertilization encour-

The C4 grass maize (*Zea mays* L.) is the third most vital food crop worldwide in the relation of the invention, and its claim is prophesied to rise by 45% from 1997 to 2020 [10]. Educations with maize retort to dual the ambient CO2 presented variable possessions on growth fluctuating from no inspiration of yield [11] to 50% stimulation [12]. The growth and productivity of maize are expected to be pretentious by raised aCO2 and temperature. Raised temperature severely disturbs the growth, and yield of maize plants [13]. There is unpredictable information on the properties of eCO2 on the vintage of maize changing from slight positive consequence [14], no

Record of the experimentations on the influences of eCO2 and temperature on the crop yield, though, used measured atmosphere amenities like phytotron and plant growth cavities or crop growth reproduction models [13, 17]. Determination of the impact of raised CO2 on the photosynthesis tolerance to severe HS is vital to expect the plant replies for universal warming since photosynthesis is sensitive to severe HS and aCO2 upsurges slightly [18, 19]. Further, flowering is a critical element for plant generative achievement and seed-set. The increase in temperature and eCO2 is the main climate revolution issues that might influence plant suitability and associated flowering actions. Resolving the influence of these ecological issues on the flowering actions like time of days to anthesis and flowering (duration from germination till flowering) is serious to appreciate the acclimatization of crops in

**2. Interaction of eCO2 with high-temperature stress and other factors to** 

atmosphere amenities like plant growth cavities or crop growth reproduction

The impacts of eCO2 and stress factors on crops have been made using controlled

agement on crops. Widespread preceding educations have described that eCO2 meaningfully enhanced the water use efficiency (WUE), reduced transpiration frequency, abridged maize growth rate, and augmented plant height, leaf number, leaf area, growth frequency, and overall yield [6]. Furthermore, the cumulative of aCO2 disturbs precipitation equilibrium, which can alter the periodic precipitation circulation [7]. It has been predicted that this result would carry about a 10% upsurge or decline in water capitals in several areas [8]. The raised temperature, i.e., heat stress (HS) damage growth and physiological ailments, and consequentially reduce yield [9]. Increased temperature due to eCO2 has a primary effect on the food grain invention reliant on the places. With the rising temperature by 1.0–2.0°C in tropical and subtropical states and the food grain manufacture in

on the crop growth and carbon metabolism are not well known.

**128**

altering climate [20].

**climate change**

models in many studies [13]. The eCO2 contributes to global warming, causing alterations in the precipitations, water scarcity and changes at temperatures in several regions affecting the growth and development of crop plants [3]. However, the interactive effects of eCO2 and environmental stress conditions on the crop growth and carbon metabolism are not well predictable. The interactions between eCO2 and stress factors are critical to photosynthesis performance. It has been reported how stomata react to eCO2 levels, but the effects on photosynthesis performance of other environmental factors are poorly understood [21].

Numerous studies showed the combining impacts of eCO2 and drought and revealed that the machines are different from singular eCO2 and drought. The impact of combined eCO2 and drought are varying with crop stage such as during vegetative stage, and it restricted the shoot development, decreased leaf area, diminished mobilization of nutrients due to weak root growth, reduced stomatal closure, transpiration, and relative water contents (RWC). However, it enhances the resource use efficiencies of the plant, including WUE, light use efficiency (LUE), and nutrient use efficiency (NUE) at a certain level [22, 23]. Similarly, eCO2 and drought affect reproductive growth severely such as the impacts on the pollen abortion, pollination, flower formation, panicle length, panicle weight, seed formation, seed size and, yield potential of important agriculture crops [22].

Altering climate, counting eCO2, increasing temperatures, changing precipitation designs have influenced terrestrial environment assembly and function, carbon and water balance, and finally production of crops [24, 25]. Several experiments have described the biological replies to CO2 enhancement and their communication with ecological alteration at different levels [26]. The temperature has an important role in plant growth and development and regulates the several functions and enzymatic reactions in plants. Although, the increased value of temperature causes several abnormalities in plants such as reduces the chlorophyll contents, leaf growth, fresh and dry biomass, photosynthesis, and stomata limitations, inhibits the functions of several temperature-sensitive enzymes such as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Impacts of eCO2 and temperature combined stresses are very destructive at the reproductive phase. They may cause reduced pollination, spike sterility, less filling of grain, reduction of grain size and number, test weight, and yield potential of major crops [22].

It has been reported that eCO2 promotes an initial stimulation of photosynthesis by an increase of substrate or RuBisCO carboxylation activity and selfconsciousness of RuBisCO oxygenation, which might ultimately underwrite for advanced biomass in cereal crops [27, 28]. Nevertheless, growth responses over the long-standing under eCO2 conditions include a reduction of photosynthesis measurements and several regulatory mechanisms to avoid potential damage by this condition. A regulatory mechanism to maintain the growth and expansion of plants consists of the equilibrium among manufacture and removal of reactive oxygen species (ROS) at the intracellular level. This balance is continued by both enzymatic and non-enzymatic antioxidant defense systems [29–31].

The enzymatic machinery involves numerous antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), guaiacol peroxidase (POX), peroxiredoxins (Prxs), and enzymes of the ascorbateglutathione (AsAGSH) cycle. The AsAGSH includes different enzymes like ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) [30, 32]. Modifications of this enzymatic antioxidant component have been reported in studies of cereal crops under eCO2 conditions with contradictory results. Thus, the response of these antioxidants components is unclear with studies that find to increase [33], decreases [34], or no consistent alterations [35].

Besides, plant cells have non-enzymatic components that involve ascorbate and glutathione (GSH) along with phenolic acids, flavonoids, carotenoids anthocyanins, and phenolic composites. The free hydroxyl groups on the phenolic rings or the chromanol rings of these non-enzymatic compounds are responsible for their antioxidant properties [36]. The ring hydrogen atom can be given to free radicals, dropping and counteracting ROS. The phenolic compounds can lose a hydrogen atom which develops a free radical that is directly non-reactive by character delocalization in the entire ring assembly [28, 37]. Several studies reported only an increase in some of the individual phenolic compounds in cereal crops under high CO2 conditions [38].

Furthermore, crop growth responses to eCO2 rely on the tissue category, developmental stage as well as strength and duration of these conditions which also depend on the diversity of apparatuses of construction and purification of ROS, and the result of free radicals on antioxidants [39]. Several studies have reported a high production of hydrogen peroxide (H2O2) after exposure of crops to eCO2, and the concentration of H2O2 is dependent on the duration of these conditions. Besides, H2O2 production differed among various cellular compartments [40]. The outcome of elevated aCO2 meditation on growth and various antioxidant actions is superior in C3 plants to C4 plants [41, 42]. For example, rice as a C3 plant is further sensitive to the variations of the aCO2. However, there are inconsistent studies on the impacts of eCO2 on the antioxidant responses and yield of rice changing from the reduction of the growth responses [43] to increment of antioxidants components and enhancement of growth [44, 45].

Kumar et al. [46] reported that rice plants under eCO2 conditions showed modifications in electrolyte leakage, leaf water potential, proline, CAT, and POD activity as compared to ambient CO2, which assisted the plant to battle contrary effects of stressful environments. Thus, these authors suggest that undesirable possessions on rice yield subsequent from abiotic stress conditions may be moderated by the eCO2 meditations [46]. In agreement, leaves of a susceptible wheat cultivar (*Triticum aestivum* L.*cv*. Yitpi) infected with Barley yellow dwarf virus-PAV (*PadiAvenae* virus) and grown under eCO2 presented that the eCO2 conditions may decrease the oxidative stress caused by virus infection [47]. Nevertheless, more evidence for direct communicating possessions of eCO2 and biotic and abiotic stress conditions in cereal crops is necessary.

## **3. eCO2 mitigates oxidative stress in plants**

Various environmental stresses induce the production of ROS, which triggers oxidative stress in plants [30, 48, 49]. The most common ROS are O2 •−, • OH, and H2O2. In response to stressful conditions, H2O2 is mainly synthesized by photorespiration, beta (β)-oxidation, or due to the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase [30, 50]. The eCO2 can efficiently reduce the ROS level by increasing RuBisCO carboxylation along with reducing photorespiratory H2O2 production. Several reports have provided indications regarding the eCO2 influences on the mitigation of abiotic stress in plants [30, 51, 52]. Elevated CO2 known to be induced plant growth by supplying additional Carbon (C) sources, subsequently alleviates abiotic stress in plants. Although the elevated CO2 mediated particular physiological and molecular mechanisms related to abiotic stress alleviation are still to be explored. In the physiological aspect, supplying extra C by eCO2 leads to induce stomatal closing, improves WUE that protect drought stress in plants [53]. However, abiotic stress-induced ROS (e.g., O2 •−, • OH, and H2O2) and cellular oxidative damages (e.g., protein oxidation, lipid peroxidation) are involved in non-stomatal factors with metabolic changes [30, 54].

**131**

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops*

A systematic study of recently published articles addressed the two major hypotheses such as enhancement of antioxidant (antioxidant hypothesis) and reduction of stress impact (relaxation hypothesis) by reducing ROS generation in the plant under stressful conditions [30, 51, 55]. Several reports have been found in favor of the relaxation hypothesis in plants in response to eCO2 under stressful conditions. The ROS level was found to be reduced by eCO2 in plants under drought, and heat stresses through increasing RuBisCO carboxylation as well as reducing the level of photorespiratory H2O2 [51]. In the same study, glycine/serine (Gly/Ser) ration, glycolate oxidase (GO), and hydroxypiruvate reductase (HPR) level were evaluated as an indicator of photorespiration, which was found to be decreased in response to eCO2 under drought and heat stresses. In barley, these all parameters were found at a lower level in response to eCO2 [56]. Moreover, reduced photorespiration is correlated to the decreased level of NADPH oxidase. Therefore, a combined effect of lower photorespiration and NADPH oxidase responses may

According to the antioxidant approach, the availability of additional C by eCO2 enhances antioxidant molecules, which increase ROS scavenging activity as well as protects grapevine and tomato plants from abiotic stress induced-oxidative damages [57, 58]. More specifically, higher C availability due to eCO2 may enhance the supply of defense molecules, which improve protection against oxidative injury (antioxidant hypothesis) under stressful conditions in plant cells. However, changes in antioxidant levels are not specific, or C3 or C4 based metabolism, or not for a particular group of species. It has been reported in C4 plants that photorespiration mildly active, in which eCO2 reduces ROS level as well as oxidative injury without alteration of antioxidants level. It suggests a distinct non-stomatal process that except antioxidant defense or reduces photorespiration processes. Besides, several reports have provided the evidence regarding eCO2 reduces NADPH oxidase activity and ROS formation in mitochondria and chloroplast in plants [59, 60], but the

The ascorbate-glutathione (ASC-GSH) cycle is one of the major mechanisms for stress-induced H2O2 regulation. However, only limited reports have been found concerning eCO2 mediated changes of ASC-GSH cycle components in plants under stress conditions. For example, HS alleviated through enhancement of DHAR, MDHAR, APX, and GR in tomato [58]. Similarly, GR and APX were found to be increased by eCO2 in wheat under ozone stress [61]. Also, responses of ASC-GSH cycle components varied based on the plant species and experimental set-up. Therefore, additional studies are needed concerning the eCO2 mediated oxidative stress alleviation as well as enhancement of ASC-GSH cycle components in plants

Several researchers on the consequences of eCO2 and stress factors on crops have been made using monitored situation amenities like plant growth chambers, free-air concentration enrichment (FACE) experiment, open-top chamber (OTC) or stimulated crop growth models [13]. The eCO2 contributes to global warming causing alterations in the precipitations patterns, water scarcity, flood, and changes at extreme temperatures in several regions affecting the growth and development of plants [3]. However, the interactive effects of eCO2 and environmental stress conditions on the development of crops and metabolism are not well documented. It has been shown the average reduction of stomatal conductance (20–30%), stomatal density (5–7%), stomatal developments, and increment in WUE (8–18%)

*DOI: http://dx.doi.org/10.5772/intechopen.94128*

lead to reduce H2O2 in plants.

under abiotic stresses.

activity of beta (β)-oxidation is still to be explored.

**4. eCO2 improves photosynthesis under high temperature**

#### *Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops DOI: http://dx.doi.org/10.5772/intechopen.94128*

*Abiotic Stress in Plants*

enhancement of growth [44, 45].

in cereal crops is necessary.

**3. eCO2 mitigates oxidative stress in plants**

Besides, plant cells have non-enzymatic components that involve ascorbate and glutathione (GSH) along with phenolic acids, flavonoids, carotenoids anthocyanins, and phenolic composites. The free hydroxyl groups on the phenolic rings or the chromanol rings of these non-enzymatic compounds are responsible for their antioxidant properties [36]. The ring hydrogen atom can be given to free radicals, dropping and counteracting ROS. The phenolic compounds can lose a hydrogen atom which develops a free radical that is directly non-reactive by character delocalization in the entire ring assembly [28, 37]. Several studies reported only an increase in some of the individual phenolic compounds in cereal crops under high CO2 conditions [38]. Furthermore, crop growth responses to eCO2 rely on the tissue category, developmental stage as well as strength and duration of these conditions which also depend on the diversity of apparatuses of construction and purification of ROS, and the result of free radicals on antioxidants [39]. Several studies have reported a high production of hydrogen peroxide (H2O2) after exposure of crops to eCO2, and the concentration of H2O2 is dependent on the duration of these conditions. Besides, H2O2 production differed among various cellular compartments [40]. The outcome of elevated aCO2 meditation on growth and various antioxidant actions is superior in C3 plants to C4 plants [41, 42]. For example, rice as a C3 plant is further sensitive to the variations of the aCO2. However, there are inconsistent studies on the impacts of eCO2 on the antioxidant responses and yield of rice changing from the reduction of the growth responses [43] to increment of antioxidants components and

Kumar et al. [46] reported that rice plants under eCO2 conditions showed modifications in electrolyte leakage, leaf water potential, proline, CAT, and POD activity as compared to ambient CO2, which assisted the plant to battle contrary effects of stressful environments. Thus, these authors suggest that undesirable possessions on rice yield subsequent from abiotic stress conditions may be moderated by the eCO2 meditations [46]. In agreement, leaves of a susceptible wheat cultivar (*Triticum aestivum* L.*cv*. Yitpi) infected with Barley yellow dwarf virus-PAV (*PadiAvenae* virus) and grown under eCO2 presented that the eCO2 conditions may decrease the oxidative stress caused by virus infection [47]. Nevertheless, more evidence for direct communicating possessions of eCO2 and biotic and abiotic stress conditions

Various environmental stresses induce the production of ROS, which triggers

cellular oxidative damages (e.g., protein oxidation, lipid peroxidation) are involved

H2O2. In response to stressful conditions, H2O2 is mainly synthesized by photorespiration, beta (β)-oxidation, or due to the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase [30, 50]. The eCO2 can efficiently reduce the ROS level by increasing RuBisCO carboxylation along with reducing photorespiratory H2O2 production. Several reports have provided indications regarding the eCO2 influences on the mitigation of abiotic stress in plants [30, 51, 52]. Elevated CO2 known to be induced plant growth by supplying additional Carbon (C) sources, subsequently alleviates abiotic stress in plants. Although the elevated CO2 mediated particular physiological and molecular mechanisms related to abiotic stress alleviation are still to be explored. In the physiological aspect, supplying extra C by eCO2 leads to induce stomatal closing, improves WUE that protect drought stress

•−, •

•−, •

OH, and

OH, and H2O2) and

oxidative stress in plants [30, 48, 49]. The most common ROS are O2

in plants [53]. However, abiotic stress-induced ROS (e.g., O2

in non-stomatal factors with metabolic changes [30, 54].

**130**

A systematic study of recently published articles addressed the two major hypotheses such as enhancement of antioxidant (antioxidant hypothesis) and reduction of stress impact (relaxation hypothesis) by reducing ROS generation in the plant under stressful conditions [30, 51, 55]. Several reports have been found in favor of the relaxation hypothesis in plants in response to eCO2 under stressful conditions. The ROS level was found to be reduced by eCO2 in plants under drought, and heat stresses through increasing RuBisCO carboxylation as well as reducing the level of photorespiratory H2O2 [51]. In the same study, glycine/serine (Gly/Ser) ration, glycolate oxidase (GO), and hydroxypiruvate reductase (HPR) level were evaluated as an indicator of photorespiration, which was found to be decreased in response to eCO2 under drought and heat stresses. In barley, these all parameters were found at a lower level in response to eCO2 [56]. Moreover, reduced photorespiration is correlated to the decreased level of NADPH oxidase. Therefore, a combined effect of lower photorespiration and NADPH oxidase responses may lead to reduce H2O2 in plants.

According to the antioxidant approach, the availability of additional C by eCO2 enhances antioxidant molecules, which increase ROS scavenging activity as well as protects grapevine and tomato plants from abiotic stress induced-oxidative damages [57, 58]. More specifically, higher C availability due to eCO2 may enhance the supply of defense molecules, which improve protection against oxidative injury (antioxidant hypothesis) under stressful conditions in plant cells. However, changes in antioxidant levels are not specific, or C3 or C4 based metabolism, or not for a particular group of species. It has been reported in C4 plants that photorespiration mildly active, in which eCO2 reduces ROS level as well as oxidative injury without alteration of antioxidants level. It suggests a distinct non-stomatal process that except antioxidant defense or reduces photorespiration processes. Besides, several reports have provided the evidence regarding eCO2 reduces NADPH oxidase activity and ROS formation in mitochondria and chloroplast in plants [59, 60], but the activity of beta (β)-oxidation is still to be explored.

The ascorbate-glutathione (ASC-GSH) cycle is one of the major mechanisms for stress-induced H2O2 regulation. However, only limited reports have been found concerning eCO2 mediated changes of ASC-GSH cycle components in plants under stress conditions. For example, HS alleviated through enhancement of DHAR, MDHAR, APX, and GR in tomato [58]. Similarly, GR and APX were found to be increased by eCO2 in wheat under ozone stress [61]. Also, responses of ASC-GSH cycle components varied based on the plant species and experimental set-up. Therefore, additional studies are needed concerning the eCO2 mediated oxidative stress alleviation as well as enhancement of ASC-GSH cycle components in plants under abiotic stresses.

#### **4. eCO2 improves photosynthesis under high temperature**

Several researchers on the consequences of eCO2 and stress factors on crops have been made using monitored situation amenities like plant growth chambers, free-air concentration enrichment (FACE) experiment, open-top chamber (OTC) or stimulated crop growth models [13]. The eCO2 contributes to global warming causing alterations in the precipitations patterns, water scarcity, flood, and changes at extreme temperatures in several regions affecting the growth and development of plants [3]. However, the interactive effects of eCO2 and environmental stress conditions on the development of crops and metabolism are not well documented. It has been shown the average reduction of stomatal conductance (20–30%), stomatal density (5–7%), stomatal developments, and increment in WUE (8–18%)

under eCO2 conditions. However, these changes vary with the crop species, developmental stages, nature of stressors and duration, surrounding environments, and plant attributes [62]. Likewise, the interactions between an eCO2 with stress factors are crucial to understanding the photosynthesis performance. Therefore, there is a considerable deviation in the light-saturated photosynthetic assimilation rate under eCO2 rely upon the plant type, plant functional traits, micro or surrounding environment, and resource availability. For instance, the stimulation in photosynthetic assimilation rate under eCO2 is varied from 30 to 80% (strong stimulations in C3 species as compared to C4) in FACE experiment or pot conditions but diminished in field conditions because of the integration of other multiple stressors such as drought, heat, flood and nutrient deficiencies.

In this regard, several studies were conducted to observe the combining effects of eCO2 and drought and reveals that the growth mechanisms are distinct to the singular eCO2 or drought. The combined stress resulted in the longer retention time of dissolved organic carbon (accumulation of soil organic C), induce invertase and catalase activity in the soil, and ameliorate stress conditions via improving plant physiological traits and activates feedback mechanisms [63]. Further, it limits the activity of some antioxidant enzymes such as proline and MDA content and stimulates others such as SOD, CAT, and GPX [46, 64]. Abscisic acid, calcium-dependent protein kinase and glutathione *S*-transferase (GST) play an important role in the amelioration of drought stress responses by inducing signaling mechanisms under the combined form. Conclusively, it is suggested that drought and HS generate ROS, and affect the antioxidant defense mechanism of plants, which might be ameliorated by the eCO2 via stimulation of antioxidant defense enzymes [51, 62]. Similarly, eCO2 combined with drought and HS regulates the sugars (starch, sucrose) and amino acids (alanine, pyruvate, arginine, glutamate) and secondary metabolites (coumaric acid, salicylic acid) metabolism, protective proteins and readjusted the metabolic, redox, and osmotic equilibrium of plants under combined eCO2 and drought [65, 66].

The impact of combined eCO2 and drought are varied with crop stage such as during the vegetative phase decreased the shoot elongation and leaf area, diminished mobilization of nutrients due to weak root growth, reduced stomatal conductance by increasing stomatal resistance and stomatal movements, plant hydraulic conductance, aquaporins, and reduce transpiration and RWC. However, at certain levels, it enhances the biomass allocations to the reproductive part, improves resource use efficiencies of plants including WUE, LUE, and NUE [67]. Similarly, eCO2 and drought affect reproductive growth severely such as its impacts on the assimilate partitioning, pollen abortion, pollination, flower formation, panicle length, panicle weight, productive tiller number, seed formation, seed size, and yield potential of important crops [22, 68]. Besides the yield potential, eCO2 decreased the grain quality via affecting macro- and micro-nutrients content such as phosphorus (P), Sulphur (S), and Iron (Fe), Zinc (Zn) contents of dryland legumes, which further associated with yield dilutions [23].

Several findings have stated the biological responses to CO2 enhancement and their communication with conservation alteration at diverse levels [26]. In these aspects, the temperature has an important role in plant growth and development and regulates the several functions and enzymatic reactions in plants. Although, the increased value of temperature cause several abnormalities in plants such as change the emission of volatile organic compounds, reduce nitrogen uptake, chlorophyll contents, leaf growth, fresh and dry biomass, photosynthesis, and stomata limitations (by membrane damage and photosystem II (PSII) activity), enhance the activity of mitochondrial electron transport, stress proteins and plant growth regulators, limitation of several temperature-sensitive enzymes such as RuBisCO.

**133**

climatic conditions [79].

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops*

quality, and yield potential of major crops [20, 22, 69].

senger signaling, and expression of stress proteins.

**5. eCO2 improves yield under high temperature**

would also accelerate the procedure of growth in plants [58, 74].

The combined effects of eCO2 and temperature stresses are very destructive at the reproductive phase. They may cause changes in flowering time, pollination, spike sterility, less filling of grain, reduction of grain size and number, test weight, grain

Besides the drought and HS (major), other stressors also interact with the eCO2 under field conditions and influence the plant growth and development. For instance, eCO2 and salt stress conditions influence the nitrogen metabolism, water balance, photosynthetic inhibitions, nutrient deficiency or toxicity, stomatal conductance, carbohydrate metabolism, phenolic enrichments, and generation of secondary metabolites [63, 70]. Similarly, limited nitrogen supply under eCO2 modifies the C/N ratio, nitrogen metabolism, protein supply, protein structure, gene expression, sugar metabolism, and decreases antioxidant enzyme, amino acid synthesis, photosynthetic pigments, and elevated ROS, which influence the redox equilibrium and leads to early senescence in plants [71]. Likewise, under N limitations, the photosynthetic rate is more affected in C3 species (because of more N requirement for RuBisCO synthesis), and eCO2 could help in mitigation of N limitations by reducing photorespiration, elevating starch level, increase chloroplast size, higher stomatal resistance, mitochondrial respiration, metabolites and dilution of chlorophyll concentrations [62]. Therefore, the eCO2 and stressors impacts have differed than singular stress, and up to a certain level of eCO2 try to recover plants via inducing defense machinery, feedback mechanisms, activating secondary mes-

By the end of the 21st century, CO2 is expected to rise from the current level 370 μmol·mol−1 to 540–970 μmol·mol−1, and about to grasp 550 μmol·mol−1 near 2050 and 750 μmol·mol−1 in 2100. In the meantime, Earth's global temperature will rise by about 2–4°C [72]. The increased concentration of CO2 in the atmosphere would increase the temperature of Earth that is why global heating will develop, the most important aspect of upcoming climate variation. The relations between the temperature and CO2 will have an intense effect on global agricultural production and the Earth's environment [73]. The rise in the atmospheric temperature and CO2

Climate change impacts on crop growth are becoming global concerns. They are particularly important for food supply and sustainable agricultural development [75, 76]. CO2 concentration and temperature are two key factors affecting crop growth, development and yield [77]. Combined or individual possessions of temperature increase and eCO2 meditation change on crop growth and yield during the recent decades have been observed [78]. For instance, the modeled improvements in soybean absorption of CO2 with an increase in the growing season temperature, and aCO2 hindered the photorespiration by 23–48%, which depends on the future

The growth and distribution of crops are reduced by environmental factors like CO2 and temperature. The production of the biomass of modern C3 plants was decreased by 50% when it was grown at a low concentration of CO2 (180–220 ppm), while the other conditions were optimal. Crops need the almost dual amount of water at 2°C increase in temperatures at a higher elevation of agricultural plains. Elevated CO2 concentration increases the yield of the crop once the substrate for the photosynthesis process of leaf and the incline of CO2 absorption of air increases. C3 plants are more benefitted at eCO2 than C4 plants [80]. However, the doubling of CO2 does not deteriorate the adverse effects of high temperature on the reproductive

*DOI: http://dx.doi.org/10.5772/intechopen.94128*

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops DOI: http://dx.doi.org/10.5772/intechopen.94128*

*Abiotic Stress in Plants*

drought [65, 66].

drought, heat, flood and nutrient deficiencies.

under eCO2 conditions. However, these changes vary with the crop species, developmental stages, nature of stressors and duration, surrounding environments, and plant attributes [62]. Likewise, the interactions between an eCO2 with stress factors are crucial to understanding the photosynthesis performance. Therefore, there is a considerable deviation in the light-saturated photosynthetic assimilation rate under eCO2 rely upon the plant type, plant functional traits, micro or surrounding environment, and resource availability. For instance, the stimulation in photosynthetic assimilation rate under eCO2 is varied from 30 to 80% (strong stimulations in C3 species as compared to C4) in FACE experiment or pot conditions but diminished in field conditions because of the integration of other multiple stressors such as

In this regard, several studies were conducted to observe the combining effects of eCO2 and drought and reveals that the growth mechanisms are distinct to the singular eCO2 or drought. The combined stress resulted in the longer retention time of dissolved organic carbon (accumulation of soil organic C), induce invertase and catalase activity in the soil, and ameliorate stress conditions via improving plant physiological traits and activates feedback mechanisms [63]. Further, it limits the activity of some antioxidant enzymes such as proline and MDA content and stimulates others such as SOD, CAT, and GPX [46, 64]. Abscisic acid, calcium-dependent protein kinase and glutathione *S*-transferase (GST) play an important role in the amelioration of drought stress responses by inducing signaling mechanisms under the combined form. Conclusively, it is suggested that drought and HS generate ROS, and affect the antioxidant defense mechanism of plants, which might be ameliorated by the eCO2 via stimulation of antioxidant defense enzymes [51, 62]. Similarly, eCO2 combined with drought and HS regulates the sugars (starch, sucrose) and amino acids (alanine, pyruvate, arginine, glutamate) and secondary metabolites (coumaric acid, salicylic acid) metabolism, protective proteins and readjusted the metabolic, redox, and osmotic equilibrium of plants under combined eCO2 and

The impact of combined eCO2 and drought are varied with crop stage such as during the vegetative phase decreased the shoot elongation and leaf area, diminished mobilization of nutrients due to weak root growth, reduced stomatal conductance by increasing stomatal resistance and stomatal movements, plant hydraulic conductance, aquaporins, and reduce transpiration and RWC. However, at certain levels, it enhances the biomass allocations to the reproductive part, improves resource use efficiencies of plants including WUE, LUE, and NUE [67]. Similarly, eCO2 and drought affect reproductive growth severely such as its impacts on the assimilate partitioning, pollen abortion, pollination, flower formation, panicle length, panicle weight, productive tiller number, seed formation, seed size, and yield potential of important crops [22, 68]. Besides the yield potential, eCO2 decreased the grain quality via affecting macro- and micro-nutrients content such as phosphorus (P), Sulphur (S), and Iron (Fe), Zinc (Zn) contents of dryland

Several findings have stated the biological responses to CO2 enhancement and their communication with conservation alteration at diverse levels [26]. In these aspects, the temperature has an important role in plant growth and development and regulates the several functions and enzymatic reactions in plants. Although, the increased value of temperature cause several abnormalities in plants such as change the emission of volatile organic compounds, reduce nitrogen uptake, chlorophyll contents, leaf growth, fresh and dry biomass, photosynthesis, and stomata limitations (by membrane damage and photosystem II (PSII) activity), enhance the activity of mitochondrial electron transport, stress proteins and plant growth regulators, limitation of several temperature-sensitive enzymes such as RuBisCO.

legumes, which further associated with yield dilutions [23].

**132**

The combined effects of eCO2 and temperature stresses are very destructive at the reproductive phase. They may cause changes in flowering time, pollination, spike sterility, less filling of grain, reduction of grain size and number, test weight, grain quality, and yield potential of major crops [20, 22, 69].

Besides the drought and HS (major), other stressors also interact with the eCO2 under field conditions and influence the plant growth and development. For instance, eCO2 and salt stress conditions influence the nitrogen metabolism, water balance, photosynthetic inhibitions, nutrient deficiency or toxicity, stomatal conductance, carbohydrate metabolism, phenolic enrichments, and generation of secondary metabolites [63, 70]. Similarly, limited nitrogen supply under eCO2 modifies the C/N ratio, nitrogen metabolism, protein supply, protein structure, gene expression, sugar metabolism, and decreases antioxidant enzyme, amino acid synthesis, photosynthetic pigments, and elevated ROS, which influence the redox equilibrium and leads to early senescence in plants [71]. Likewise, under N limitations, the photosynthetic rate is more affected in C3 species (because of more N requirement for RuBisCO synthesis), and eCO2 could help in mitigation of N limitations by reducing photorespiration, elevating starch level, increase chloroplast size, higher stomatal resistance, mitochondrial respiration, metabolites and dilution of chlorophyll concentrations [62]. Therefore, the eCO2 and stressors impacts have differed than singular stress, and up to a certain level of eCO2 try to recover plants via inducing defense machinery, feedback mechanisms, activating secondary messenger signaling, and expression of stress proteins.

#### **5. eCO2 improves yield under high temperature**

By the end of the 21st century, CO2 is expected to rise from the current level 370 μmol·mol−1 to 540–970 μmol·mol−1, and about to grasp 550 μmol·mol−1 near 2050 and 750 μmol·mol−1 in 2100. In the meantime, Earth's global temperature will rise by about 2–4°C [72]. The increased concentration of CO2 in the atmosphere would increase the temperature of Earth that is why global heating will develop, the most important aspect of upcoming climate variation. The relations between the temperature and CO2 will have an intense effect on global agricultural production and the Earth's environment [73]. The rise in the atmospheric temperature and CO2 would also accelerate the procedure of growth in plants [58, 74].

Climate change impacts on crop growth are becoming global concerns. They are particularly important for food supply and sustainable agricultural development [75, 76]. CO2 concentration and temperature are two key factors affecting crop growth, development and yield [77]. Combined or individual possessions of temperature increase and eCO2 meditation change on crop growth and yield during the recent decades have been observed [78]. For instance, the modeled improvements in soybean absorption of CO2 with an increase in the growing season temperature, and aCO2 hindered the photorespiration by 23–48%, which depends on the future climatic conditions [79].

The growth and distribution of crops are reduced by environmental factors like CO2 and temperature. The production of the biomass of modern C3 plants was decreased by 50% when it was grown at a low concentration of CO2 (180–220 ppm), while the other conditions were optimal. Crops need the almost dual amount of water at 2°C increase in temperatures at a higher elevation of agricultural plains. Elevated CO2 concentration increases the yield of the crop once the substrate for the photosynthesis process of leaf and the incline of CO2 absorption of air increases. C3 plants are more benefitted at eCO2 than C4 plants [80]. However, the doubling of CO2 does not deteriorate the adverse effects of high temperature on the reproductive growth of crops or fiber quality. Therefore, increased CO2 concentration is associated with higher temperatures, crop yield, and quality that reduce particularly in areas where current temperatures are near to optimal [81].

Elevated CO2 resulted in major changes in morpho-physiological restrictions. Besides, eCO2 along with atmospheric temperatures during the phenological stages of rice cultivars showed contrasting results of the time of flowering and maturation such as eCO2 in combination with the lower atmospheric temperature that stopped flowering g in the CR-1014 cultivar while with the higher temperature increased grain yield the in Naveen cultivar [82].

Growth and photosynthesis of C3 crops are enhanced when it is grown at a high level of CO2, although, the degree of stimulation differs with temperature among cultivars as well as species. The probable decline in the transpiration process due to the partial closure of stomata in the eCO2 level is largely invalid by the energy balance between the crop and its environment, which could result in total water use in similar climate conditions. The yield of seeds is increased by an increase in the CO2 under the ideal temperature. On the other hand, at supra-optimal temperature, the yield of seeds is decreased under both raised and ambient CO2. The yield of kidney bean decreased in that region where temperatures are at or above optimal conditions in combination with increased CO2 concentration [83].

The effects of HS on the grain and biomass yield of plants depend on the duration and magnitude of HS. HS at the vegetative phase decreased the grain and biomass yield mostly by increasing plant growth and dropping the time obtainable to capture possessions, and also by dropping the rate of photosynthesis [84]. At the anthesis or flowering phase, HS decreases the amount of grain due to pollen abortion. In contrast, at the grain-filling phase, HS decreases the heaviness of grain by restraining the translocation of integrating, and margarine the period of grainfilling [85, 86].

Notably, eCO2 may lessen the harmful influence of heat stress on the grain and biomass yield by inspiration of photosynthesis, defense of the photosynthetic devices from HS injury, and improvement in the water status of plants owing to reduced transpiration. Moreover, high levels of hexoses and sucrose in plants with eCO2 are related to increase fertile florets and dry spike mass [87], and osmotic modification [88], which can develop heat stress tolerance [89]. It is hypothesized that HS at anthesis has a drastic impact on the grain yield and plant biomass, but it has a less impact eCO2 than ambient CO2 [90].

#### **6. Conclusion**

It is very important to know that the impacts of climate change on crop growth are becoming global concerns. Interactive effects of eCO2 and environmental stress conditions on crop growth and carbon metabolism are not well predictable. The influence of eCO2 with the connection of temperature is considerable on crops under stress environments. The CO2 concentration improves the productivity of crops because of improved carbon exchange rates, and superior vegetative and reproductive growth. In contrast, crop productivity is decreased with increased temperatures. Hence, there is a need to develop genotypes that are different intolerant to various environments or to identify genotypes that perform better under predicted climate change. In this review, cereal genotypes have been characterized by differing responses to eCO2 and HS and identified the mechanisms of tolerance to HS. It can promote the crop potential to assist the breeding program for the development of new genotypes tolerance to HS.

**135**

**Author details**

Abdul Rehman7

Kafrelsheikh, Egypt

Muhammad Aamir Iqbal5

Ayman EL Sabagh1,2\*, Akbar Hossain3

provided the original work is properly cited.

, Ali Raza6

Muhammad Ali Raza11, Muhammad Mubeen12, Wajid Nasim13,

Celaleddin Barutçular14, Ram Swaroop Meena15 and Hirofumi Saneoka16

1 Department of Agronomy, Faculty of Agriculture, Kafrelsheikh University,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

, Md Atikur Rahman8

, Mohammad Sohidul Islam4

, Rajesh Kumar Singhal9

, Çetin Karademir2

,

, Analía Llanes10,

,

, Emine Karademir2

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops*

Authors declare that no conflict of interest could arise.

*DOI: http://dx.doi.org/10.5772/intechopen.94128*

The authors declare no conflicts of interest.

**Conflicts of interest**

**Disclosure statement**

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops DOI: http://dx.doi.org/10.5772/intechopen.94128*

## **Conflicts of interest**

*Abiotic Stress in Plants*

growth of crops or fiber quality. Therefore, increased CO2 concentration is associated with higher temperatures, crop yield, and quality that reduce particularly in

Elevated CO2 resulted in major changes in morpho-physiological restrictions. Besides, eCO2 along with atmospheric temperatures during the phenological stages of rice cultivars showed contrasting results of the time of flowering and maturation such as eCO2 in combination with the lower atmospheric temperature that stopped flowering g in the CR-1014 cultivar while with the higher temperature increased

Growth and photosynthesis of C3 crops are enhanced when it is grown at a high level of CO2, although, the degree of stimulation differs with temperature among cultivars as well as species. The probable decline in the transpiration process due to the partial closure of stomata in the eCO2 level is largely invalid by the energy balance between the crop and its environment, which could result in total water use in similar climate conditions. The yield of seeds is increased by an increase in the CO2 under the ideal temperature. On the other hand, at supra-optimal temperature, the yield of seeds is decreased under both raised and ambient CO2. The yield of kidney bean decreased in that region where temperatures are at or above optimal conditions in combination with increased

The effects of HS on the grain and biomass yield of plants depend on the duration and magnitude of HS. HS at the vegetative phase decreased the grain and biomass yield mostly by increasing plant growth and dropping the time obtainable to capture possessions, and also by dropping the rate of photosynthesis [84]. At the anthesis or flowering phase, HS decreases the amount of grain due to pollen abortion. In contrast, at the grain-filling phase, HS decreases the heaviness of grain by restraining the translocation of integrating, and margarine the period of grain-

Notably, eCO2 may lessen the harmful influence of heat stress on the grain and biomass yield by inspiration of photosynthesis, defense of the photosynthetic devices from HS injury, and improvement in the water status of plants owing to reduced transpiration. Moreover, high levels of hexoses and sucrose in plants with eCO2 are related to increase fertile florets and dry spike mass [87], and osmotic modification [88], which can develop heat stress tolerance [89]. It is hypothesized that HS at anthesis has a drastic impact on the grain yield and plant biomass, but it

It is very important to know that the impacts of climate change on crop growth are becoming global concerns. Interactive effects of eCO2 and environmental stress conditions on crop growth and carbon metabolism are not well predictable. The influence of eCO2 with the connection of temperature is considerable on crops under stress environments. The CO2 concentration improves the productivity of crops because of improved carbon exchange rates, and superior vegetative and reproductive growth. In contrast, crop productivity is decreased with increased temperatures. Hence, there is a need to develop genotypes that are different intolerant to various environments or to identify genotypes that perform better under predicted climate change. In this review, cereal genotypes have been characterized by differing responses to eCO2 and HS and identified the mechanisms of tolerance to HS. It can promote the crop potential to assist the breeding program for the

areas where current temperatures are near to optimal [81].

grain yield the in Naveen cultivar [82].

has a less impact eCO2 than ambient CO2 [90].

development of new genotypes tolerance to HS.

CO2 concentration [83].

filling [85, 86].

**6. Conclusion**

**134**

The authors declare no conflicts of interest.

## **Disclosure statement**

Authors declare that no conflict of interest could arise.

## **Author details**

Ayman EL Sabagh1,2\*, Akbar Hossain3 , Mohammad Sohidul Islam4 , Muhammad Aamir Iqbal5 , Ali Raza6 , Çetin Karademir2 , Emine Karademir2 , Abdul Rehman7 , Md Atikur Rahman8 , Rajesh Kumar Singhal9 , Analía Llanes10, Muhammad Ali Raza11, Muhammad Mubeen12, Wajid Nasim13, Celaleddin Barutçular14, Ram Swaroop Meena15 and Hirofumi Saneoka16

1 Department of Agronomy, Faculty of Agriculture, Kafrelsheikh University, Kafrelsheikh, Egypt

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 Department of Field Crops, Faculty of Agriculture, Siirt University, Turkey

3 Bangladesh Wheat and Maize Research Institute, Dinajpur, Bangladesh

4 Department of Agronomy, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh

5 Department of Agronomy, University of Poonch Rawalakot Azadkashmir, Pakistan

6 Key Lab of Biology and Genetic Improvement of Oil Crops, Oil Crops Research Institute, Chinese Academy of Agricultural Sciences (CAAS), Wuhan, China

7 Department of Crop Sciences and Biotechnology, Dankook University, 119, Dandae-ro, Dongnam-gu, Cheonan-si, Korea

8 Grassland and Forage Division, National Institute of Animal Science, Rural Development Administration, Cheonan, Korea

9 ICAR-Indian Grassland and Fodder Research Institute, Jhansi, India

10 Plant Physiology Laboratory, Universidad Nacional de Río Cuarto (UNRC)-Instituto Nacional de Investigaciones Agrobiotecnológicas (INIAB), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Río Cuarto, Argentina

11 College of Agronomy, Sichuan Agricultural University, Chengdu, P.R. China

12 Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus, Pakistan

13 Department of Agronomy, University College of Agriculture and Environmental Sciences, The Islamia University of Bahawalpur (IUB), Bahawalpur, Pakistan

14 Department of Field Crops, Faculty of Agriculture, Cukurova University, Turkey

15 Department of Agronomy, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, UP, India

16 Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Japan

\*Address all correspondence to: aymanelsabagh@agr.kfs.edu.eg

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**137**

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops*

Bulletin of American Meteorological

[8] Wallace JS. Increasing agricultural water use efficiency to meet future food production. Agriculture, Ecosystems &Environment. 2000;**82**:105-119

[10] Young KJ, Long SP. Crop ecosystem responses to climatic change: maize and sorghum. In: Reddy KR, Hodges HF (Eds.). Climate change and global crop productivity, CABI International, Oxon, United Kingdom; 2000. pp. 107-131

[11] Hunt R, Hand D, Hannah M, Neal A. Response to CO2 enrichment in 27 herbaceous species. Functional

[12] Rogers HH, Dahlman RC. Crop responses to CO2 enrichment. CO2 and biosphere. Advances in vegetation

[13] Pathak H, Aggarwal PK, Singh SD. Climate change impacts, adaptations and mitigation in agriculture: methodology for assessment and application, Indian Agricultural Research Institute, New Delhi, India,

Ecology. 1991;**5**:410-421

Science. 1993;14:117-131

[14] Leakey A, Uribelarrea M,

[15] Kim SH, Gitz DC, Sicher RC, Baker JT, Timlin DJ. Temperature

Ainsworth E, Naidu S, Rogers A, et al. Photosynthesis, productivity and yield of maize are not affected by open-air elevation of CO2 concentration in the absence of drought. Plant Physiology.

2012;pp. 1-302

2006;140:779-790

[9] Johkan M, Oda M, Maruo T, Shinohara Y. Crop Production and Global Warming Impacts, Case Studies on the Economy, Human Health, and on Urban and Natural Environments. 2011;**9**:139-152. http://www.intechopen.

com.

Society. 2000;**81:**417-425

*DOI: http://dx.doi.org/10.5772/intechopen.94128*

[1] Raza A, Razzaq A, Mehmood SS, Zou X, Zhang X, Lv Y, Xu J. Impact of climate change on crops adaptation and strategies to tackle its outcome: A

[2] Hossain A, Farooq M, EL Sabagh A, Hasanuzzaman M, Erman M, Islam T. Morphological, Physiobiochemical and Molecular Adaptability of Legumes of Fabaceae to Drought Stress, with Special Reference to *Medicago sativa* L. In: Hasanuzzaman M, Araújo S, Gill S. (eds) The Plant Family Fabaceae.

review. Plants. 2019;**8**:34

**References**

Springer, Singapore; 2020. pp. 289-317. https://doi.org/10.1007/

[3] IPCC. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri RK, Meyer LA (eds.)]. IPCC, Geneva, Switzerland, 2014. p.151

[4] Calzadilla A, Zhu T, Rehdanz K, Tol RSJ, Ringler C. Economy wide impacts of climate change on agriculture in Sub-Saharan Africa. Ecological Economics.2013;**93**:150-165

[5] Cairns JE, Sonder K, Zaidi PH, Verhulst N, Mahuku G, et al. Maize Production in a Changing Climate: Impacts, Adaptation, and Mitigation Strategies. Advances in Agronomy.

[6] Ziska L. Observed changes in soyabean growth and seed yield from *Abutilon theophrasti* competition as a function of carbon dioxide concentration. Weed Research.

[7] Easterling DR, Evans JL, Groisman PY, Karl TR, Kunkel KE, et al. Observed variability and trends in extreme climate events: a brief review.

2012;**114:**1-65

2013;53:140-145

978-981-15-4752-2\_11.

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops DOI: http://dx.doi.org/10.5772/intechopen.94128*

#### **References**

*Abiotic Stress in Plants*

University, Dinajpur, Bangladesh

Dandae-ro, Dongnam-gu, Cheonan-si, Korea

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Turkey

Pakistan

Wuhan, China

Argentina

Turkey

Vehari Campus, Pakistan

University, Varanasi, UP, India

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provided the original work is properly cited.

2 Department of Field Crops, Faculty of Agriculture, Siirt University,

3 Bangladesh Wheat and Maize Research Institute, Dinajpur, Bangladesh

4 Department of Agronomy, Hajee Mohammad Danesh Science and Technology

5 Department of Agronomy, University of Poonch Rawalakot Azadkashmir,

7 Department of Crop Sciences and Biotechnology, Dankook University, 119,

8 Grassland and Forage Division, National Institute of Animal Science, Rural

(UNRC)-Instituto Nacional de Investigaciones Agrobiotecnológicas (INIAB), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Río Cuarto,

11 College of Agronomy, Sichuan Agricultural University, Chengdu, P.R. China

12 Department of Environmental Sciences, COMSATS University Islamabad,

14 Department of Field Crops, Faculty of Agriculture, Cukurova University,

15 Department of Agronomy, Institute of Agricultural Sciences, Banaras Hindu

16 Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: aymanelsabagh@agr.kfs.edu.eg

13 Department of Agronomy, University College of Agriculture and Environmental Sciences, The Islamia University of Bahawalpur (IUB), Bahawalpur, Pakistan

9 ICAR-Indian Grassland and Fodder Research Institute, Jhansi, India

10 Plant Physiology Laboratory, Universidad Nacional de Río Cuarto

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[6] Ziska L. Observed changes in soyabean growth and seed yield from *Abutilon theophrasti* competition as a function of carbon dioxide concentration. Weed Research. 2013;53:140-145

[7] Easterling DR, Evans JL, Groisman PY, Karl TR, Kunkel KE, et al. Observed variability and trends in extreme climate events: a brief review.

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[75] Tan K, Zhou G, Lv X, Guo J, Ren S. Combined effects of elevated temperature and CO2 enhance threat from low temperature hazard to winter wheat growth in North China. Scientific Reports. 2018;**8**:1-9

[76] EL Sabagh A, Hossain A, Barutçular C, Gormus O, Ahmad Z, Hussain S, Islam MS, Alharby H, Bamagoos A, Kumar N, Akdeniz A, Fahad S, Meena RS, Abdelhamid M, Wasaya A, Hasanuzzaman M, Sorour S, Saneoka H. Effects of drought stress on the quality of major oilseed crops: implications and possible mitigation strategies–a review. Appllied Ecology and Environmental Research. 2019;**17**:4019-4043. https://doi. org/10.15666/aeer/1702\_40194043

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[79] Walker BJ, VanLoocke A, Bernacchi CJ, Ort DR. The costs of photorespiration to food production now and in the future. Annual Review of Plant Biology. 2016;**67**:107-129.

[80] Madan P, Jagadish S, Craufurd P, Fitzgerald M, Lafarge T, Wheeler T. Effect of elevated CO2 and high temperature on seed-set and grain quality of rice. Journal of Experimental Botany. 2012;**63**:3843-3852

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*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops*

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[90] Chavan SG, Duursma RA,

Tausz M, Ghannoum O. ECO2alleviates the negative impact of heat stress on wheat physiology but not on grain yield. Journal of Experimental Botany.2019;**70**:6447-6459. doi:10.1093/

2013;**199**:340-350

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[83] Prasad PV, Boote KJ, Allen Jr LH, Thomas JM. Effects of elevated temperature and carbon dioxide on seed-set and yield of kidney bean (*Phaseolus vulgaris* L.). Global Change

[84] Lobell DB, Gourdji SM. The influence of climate change on global crop productivity. Plant Physiology. 2012;**160**:1686-1697. Doi: https://doi.

[85] Farooq M, Bramley H, Palta JA, Siddique KHM. Heat stress in wheat during reproductive and grain-filling phases. Critical Reviewsin Plant

Sciences. 2011;**30**:491-507.DOI: 10.1080/

[86] Prasad PVV, Djanaguiraman M. Response of floret fertility and individual grain weight of wheat to high temperature stress: sensitive stages and thresholds for temperature and duration. Functional Plant Biology. 2014;**41**:1261-1269.http://dx.doi.

[87] Dreccer MF, Wockner KB, Palta JA,

McIntyre CL, Borgognone MG, Bourgault M, Reynolds M, Miralles DJ. More fertile florets and grains per spike can be achieved at higher temperature in wheat lines with high spike biomass and sugar content at booting. Functional Plant Biology 2014;**41**:482-495.http://

dx.doi.org/10.1071/FP13232.

[88] Wahid A, Gelani S, Ashraf M, Foolad MR. Heat tolerance in plants:

Biology. 2002;**8**:710-721

org/10.1104/pp.112.208298

07352689.2011.615687

org/10.1071/FP14061

*Elevated CO2 Concentration Improves Heat-Tolerant Ability in Crops DOI: http://dx.doi.org/10.5772/intechopen.94128*

temperature: cotton. Journal of Crop Improvement. 2005;**13**:157-191

*Abiotic Stress in Plants*

[69] Vicente R, Bolger AM, Martinez-Carrasco R, Pérez P,

Plant Science. 2019;**10**:1605.

[70] Sgherri C, Pérez-López U, Micaelli F, Miranda-Apodaca J, Mena-Petite A, Muñoz-Rueda A, Quartacci MF. Elevated CO2 and salinity are responsible for phenolicsenrichment in two differently pigmented lettuces. Plant Physiology and Biochemistry. 2017;**115**:269-278

[71] Agüera E, De la Haba P. Leaf senescence in response to elevated atmospheric CO2 concentration and low nitrogen supply. Biologia Plantarum.

[72] Collins M, Knutti R, Arblaster J, Dufresne JL, Fichefet T, Friedlingstein P,

….Krinner G. Long-term climate change: projections, commitments and irreversibility. In Climate Change 2013. The Physical Science Basis: Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press.

2018;**62**:401-408

2013. pp. 1029-1136

2014;**111**:3268-3273

[73] Rosenzweig C, Elliott J, Deryng D, Ruane AC, Müller C, Arneth A, ….Khabarov N. Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison. Proceedings of the National Academy of Sciences.

[74] Cai C, Yin X, He S, Jiang W, Si C, Struik PC, . . .Xiong Y. Responses of wheat and rice to factorial combinations of ambient and elevated CO2 and temperature in FACE experiments. Global Change Biology. 2016;**22**:856-874

Gutiérrez E, Usadel B, Morcuende R. De novo transcriptome analysis of durum wheat flag leaves provides new insights into the regulatory response to elevated CO2 and high temperature. Frontiers in

[75] Tan K, Zhou G, Lv X, Guo J, Ren S. Combined effects of elevated temperature and CO2 enhance threat from low temperature hazard to winter wheat growth in North China. Scientific

[76] EL Sabagh A, Hossain A, Barutçular C, Gormus O, Ahmad Z, Hussain S, Islam MS, Alharby H, Bamagoos A, Kumar N, Akdeniz A, Fahad S, Meena RS, Abdelhamid M, Wasaya A, Hasanuzzaman M, Sorour S, Saneoka H. Effects of drought stress on the quality of major oilseed crops: implications and possible mitigation strategies–a review. Appllied Ecology

and Environmental Research. 2019;**17**:4019-4043. https://doi. org/10.15666/aeer/1702\_40194043

wcc.2019.179.

Ziska L, Izaurralde RC,

2011;**103**:351-370

[77] Mubeen M. et al. Evaluating the climate change impact on crop water requirement of cotton- wheat in semi-arid conditions using DSSAT model. Journal of Water and Climate Change. 2019; 201979. doi: 10.2166/

[78] Hatfield JL, Boote KJ, Kimball B,

Ort D, . . . Wolfe D. Climate impacts on agriculture: implications for crop production. Agronomy Journal.

[79] Walker BJ, VanLoocke A, Bernacchi CJ, Ort DR. The costs of photorespiration to food production now and in the future. Annual Review of Plant Biology. 2016;**67**:107-129.

[80] Madan P, Jagadish S,

Botany. 2012;**63**:3843-3852

[81] Reddy KR, Vara Prasad P,

Craufurd P, Fitzgerald M, Lafarge T, Wheeler T. Effect of elevated CO2 and high temperature on seed-set and grain quality of rice. Journal of Experimental

Kakani VG. Crop responses to elevated carbon dioxide and interactions with

Reports. 2018;**8**:1-9

**142**

[82] Ziska LH. et al. Food security and climate change: on the potential to adapt global crop production by active selection to rising atmospheric carbon dioxide. Proceedings of the Royal Society B: Biological Sciences. 2012;**279**:4097-4105 http://doi. org/10.1098/rspb.2012.1005

[83] Prasad PV, Boote KJ, Allen Jr LH, Thomas JM. Effects of elevated temperature and carbon dioxide on seed-set and yield of kidney bean (*Phaseolus vulgaris* L.). Global Change Biology. 2002;**8**:710-721

[84] Lobell DB, Gourdji SM. The influence of climate change on global crop productivity. Plant Physiology. 2012;**160**:1686-1697. Doi: https://doi. org/10.1104/pp.112.208298

[85] Farooq M, Bramley H, Palta JA, Siddique KHM. Heat stress in wheat during reproductive and grain-filling phases. Critical Reviewsin Plant Sciences. 2011;**30**:491-507.DOI: 10.1080/ 07352689.2011.615687

[86] Prasad PVV, Djanaguiraman M. Response of floret fertility and individual grain weight of wheat to high temperature stress: sensitive stages and thresholds for temperature and duration. Functional Plant Biology. 2014;**41**:1261-1269.http://dx.doi. org/10.1071/FP14061

[87] Dreccer MF, Wockner KB, Palta JA, McIntyre CL, Borgognone MG, Bourgault M, Reynolds M, Miralles DJ. More fertile florets and grains per spike can be achieved at higher temperature in wheat lines with high spike biomass and sugar content at booting. Functional Plant Biology 2014;**41**:482-495.http:// dx.doi.org/10.1071/FP13232.

[88] Wahid A, Gelani S, Ashraf M, Foolad MR. Heat tolerance in plants: an overview. Environmental and Experimental Botany. 2007;**61**:199-223

[89] Shanmugam S, Kjaer KH, Ottosen CO, Rosenqvist E, Kumari Sharma D, Wollenweber B. The alleviating effect of elevated CO2 on heat stress susceptibility of two wheat (*Triticumaestivum* L.) cultivars. Journal of Agronomy and Crop Science. 2013;**199**:340-350

[90] Chavan SG, Duursma RA, Tausz M, Ghannoum O. ECO2alleviates the negative impact of heat stress on wheat physiology but not on grain yield. Journal of Experimental Botany.2019;**70**:6447-6459. doi:10.1093/ jxb/erz386

**145**

**Chapter 8**

**Abstract**

Ecological and Economic Potential

of Major Halophytes and Salt

*Anil Chinchmalatpure and Parbodh Chander Sharma*

Soil salinization is a global and climatic phenomenon that affects various spheres of life. The present rate of salinization is perilously fast because of global climate change and associated events leading to enhanced land degradation, loss of soil fertility and crop productivity. In this chapter, we tried to focus on the arid and semiarid regions of India along with our coastal zone which are economically fragile regions and need much closer attention. In future, India will face extreme pressure on its land resources in agriculture because of likely rapid degradation of these resources. Thus, salt affected soils must be brought under cultivation by adopting site specific strategies to ensure national food and nutritional security. In this regard, a comprehensive review of the major halophytes of these ecological zones, its mechanism of salt tolerance, ecological and economic potential is done. The potential applications of saline land vegetation including halophytes in climate change mitigation, phytoremediation, desalination, food, secondary metabolite and nutraceutical production, medicine, and saline agriculture have been discussed. Further, we tried to focus on popular farmer adopted halophytic species including edible ones, their uses, products of economic significance etc. which is highly imperative for effective utilization of these saline soils leading to improved livelihood and sustenance of resource poor farmers along with improved ecological balance.

**Keywords:** coastal soil, dry land, ecology, economic products, halophytes,

Food security and ecological security are the two pillars of all societies. The incessant growth of human population across the world is evident from the United Nations projection of 9.7 billion people by 2050 [1]. The global food demand is expected to rise by 70–100% and to meet this additional food demand, a predicted 50% increase in yields of the major food crops will be required [2]. Moreover, our global food security is significantly affected by drastic alterations in the climate [3]. This unpredictable change in climate has resulted in to several abiotic stresses such as salinity, drought, heat and low temperature, threatening the agricultural sustenance and productivity [4]. This has also brought about a significant spike in the occurrences of extreme climatic events like flood, cyclones, storms etc. [5]. Land degradation is one

saline vegetation, salinity stress

**1. Introduction**

Tolerant Vegetation in India

*T.V. Vineeth, Shrvan Kumar, Monika Shukla,* 

#### **Chapter 8**
