Plant Growth and Morphophysiological Modifications in Perennial Ryegrass under Environmental Stress

*Fuchun Xie, Rahul Datta and Dong Qin*

## **Abstract**

Perennial ryegrass (*Lolium perenne* L.) is a popular and important cool-season turfgrass used in parks, landscapes, sports fields, and golf courses, and it has significant ecological, environmental, and economic values. It is also widely used as forage and pasture grass for animals around the world. However, the growth of perennial ryegrass is often affected by various abiotic stresses, which cause declines in turf quality and forage production. Among abiotic stresses, drought, salinity, temperature, and heavy metal are the most detrimental factors for perennial ryegrass growth in different regions, which result in growth inhibition, cell structure damage, and metabolic dysfunction. Many researches have revealed a lot useful information for understanding the mechanism of tolerance to adverse stresses at morphophysiological level. In this chapter, we will give a systematic literature review about morphological and physiological changes of perennial ryegrass in response to main stress factors and provide detail aspects of improving perennial ryegrass resistance based on research progress. Understanding morphophysiological response in perennial ryegrass under stress will contribute to improving further insights on fundamental mechanisms of perennial ryegrass stress tolerance and providing valuable information for breeding resistance cultivars of perennial ryegrass.

**Keywords:** perennial ryegrass, morphology, physiology, abiotic stress, stress resistance

#### **1. Introduction**

Urban green areas have important various functions contributing to the quality of human health. Well-kept lawns enhance the esthetic value of the entire city and are involved in phytoremediation, leading to an improvement in the quality of the air and soil [1–4]. Perennial ryegrass (*Lolium perenne* L.) is an important and widespread perennial cool-season grass cultivated in temperate climates, originating in Europe, temperate Asia, and North Africa [5]. Perennial ryegrass is commonly used in home lawns, sport fields, and parks with rapid growth and establishing rate, and other elements for ecosystem service due to its massive root system, superior regeneration,

and tillering ability. It is also widely used as nutritive forage and pasture grass for animals around the world [6–8]. Moreover, numerous perennial ryegrass genotypes and hybrids are now released by commercial utilities [9, 10].

In fields, the growth and development process of plants needs to counteract various environmental stresses such as salinity, drought, cold, heat, and heavy metal [11–13]. Harsh environmental conditions may result in growth inhibition, cell structure damage, and metabolic dysfunction [14–20]. Moreover, stresses will further be intensified for the potential impact of climate change in future. Thus, maintaining proper growth of turfgrass with minimal inputs under abiotic stress conditions is a great challenge for turfgrass industry. This challenge could be addressed through improving the stress tolerance of turfgrass [14, 21]. Understanding morphological and physiological mechanisms of turfgrass adaptation to various abiotic stresses is a key step for the development of stress-tolerant ability and cost-effective and efficient management practices [13]. Morphophysiological mechanisms of turfgrass in abiotic stresses tolerance involve phenotypic changes, multiple physiological and biochemical response, and complex metabolic processes, such as water and nutrient relations, carbohydrate metabolism, protein metabolism, hormone metabolism, as well as antioxidant defenses [22, 23]. Current studies on morphophysiological mechanism controlling turfgrass adaptations to various growth conditions have provided important information for production of abiotic stress-tolerant germplasms and the further understanding of regulation mechanism of turfgrass response to abiotic stresses [13, 24, 25]. However, the mechanisms of the adaptive responses are integrated but are not necessarily the same [14]; thus, studies on how perennial ryegrass adapts to stress conditions will become more important with the increasing pressure of utilizing both ecological and economical strategies in the turf management. Furthermore, insights into mechanisms of stress resistance in perennial ryegrass will aid in identifying important characteristics for selecting the criteria of improving stress tolerance and will ultimately lead to better selection of new cultivars adapted to adverse environments. This chapter, therefore, focuses on an extensive overview of the current understanding of changes in physiology and growth/development of perennial ryegrass under various abiotic stresses. In addition, strategies for improving the stress tolerance of perennial ryegrass are also presented. This review can contribute to the better understanding of the mechanisms of perennial ryegrass response to environmental stresses and can provide valuable information for improving resistance characteristics of perennial ryegrass by breeding. Moreover, enhancing our understanding of physiological effects of abiotic stresses can provide guidelines for the practical management strategies of the maintenance of high-quality turf under limited resource availability.

#### **2. Abiotic stresses**

Abiotic stresses are major environmental conditions that reduce plant growth, productivity, and quality. Plants have evolved mechanisms to perceive these environmental challenges, transmit the stress signals within cells as well as between cells and tissues, and make appropriate adjustments in their growth and development for survive and reproduce [26–29]. The morphological and physiological changes of perennial ryegrass under abiotic stress will be discussed in this chapter.

#### **2.1 Responses of drought stress in perennial ryegrass**

Growth and development processes are inhibited when plant is exposed to drought stress [30–36]. Morphological adjustments, such as biomass allocation and leave

**355**

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass…*

changes, have been proposed as the key mechanisms used by turfgrass to enhance survival under drought [37]. There is a series of morphology changes in perennial ryegrass under drought stress. Drought stress reduced the turf quality (TQ ), number of live tillers and dry-matter yield [38–40]. Moreover, drought significantly enhanced root to shoot ratio (R/S) in perennial ryegrass to an less extents, depending on the intensity, the reason may be that perennial ryegrass in drought stress develop a large R/S to maintain water and nutrient uptake [39]. The leaves of perennial ryegrass under drought stress were also dramatically different from that of nonstressed perennial ryegrass, for example, under drought stress, the diurnal variation in the rate of leaf extension was smaller but the leaves tended to grow faster at night compared to normal irrigation controls; however, water stress ultimately reduced the rate of leaf extension and leaf area in perennial ryegrass [40]. Furthermore, the leaves' epidermis of perennial ryegrass under drought reduced the stomatal size and increased the numbers per unit leaf area. Drought also resulted deeper ridging on leaf ad-axial surface, smaller epidermal cells and bigger ridge angle [40]. Under drought stress, leave stomata of perennial ryegrass began to close to reduce their evapotranspiration

Drought stress causes significant physiological changes, including photosynthesis, osmotic adjustment substances, proteins, and antioxidant metabolism, in perennial ryegrass. For instance, the content of leaf total nitrogen and leaf relative water content (RWC) were tested to decrease, on the contrary, antioxidant activity including ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), amino acids such as aspartic acid, threonine, serine, glutamic acid, abscisic acid (ABA) concentration, and proline content increased under drought stress [41]. Photosynthesis is the primary process controlling plant growth and adaption to drought stress [42]. The canopy photosynthesis of perennial ryegrass at saturating light intensity was reduced by about half in the stressed field swards and by more than 80% in the stressed simulated swards [38]. Drought stress inhibits photosynthesis, which may be the result of low CO2 availability caused by stomatal closure and/or the inhibition of photochemical reactions and carbon assimilation metabolism [43]. In addition to the photosynthesis, starchis also considered as a buffer for imbalance between acquisition by photosynthesis and C-sink activities such as growth and respiration resulted from drought, also stress due to the excessive use of inorganic fertilizer [44]. However, use of green manure also has risk of xenobiotic contamination [45–47], and the soluble sugars, including sucrose, fructose and glucose, are involved in multiple physiological functions such as respiration, turgor maintenance, signaling and defense. Under drought conditions, starch of perennial ryegrass significantly decreased in shoots, but did not change in roots, which indicated that perennial ryegrass in drought condition preferentially allocates carbon not only to root growth, but also to root storage, while soluble sugars were enhanced in both shoots and roots. Accumulation of soluble sugars has been widely reported for plants upon water stress as a means to provide osmotic protection [39], which suggested that increasing of soluble sugars was benefit to plants to maintain growth and active

It is generally accepted that there is a noticeable genotypic variation in perennial ryegrass for drought stress responses. The research showed that one self-pollinating genotype "S10" showed higher RWC, shoot dry weight (SDW), proline, ABA, nitrogen and amino acid contents, and antioxidant enzymes activities in comparison with two commercial genotypes of "Vigor" and "Speedy" [41]. Proteins involved in carbon and energy metabolism, photosynthesis, tricarboxylic acid cycle (TCA) cycle, redox, and transport categories were upregulated in the two commercial genotypes of "Vigo" and "Speedy," while the protein profile of the "S10" changed

*DOI: http://dx.doi.org/10.5772/intechopen.93709*

rate (ET), at leaf water potentials below—13 bars [40].

metabolic activities under water deficit.

#### *Plant Growth and Morphophysiological Modifications in Perennial Ryegrass… DOI: http://dx.doi.org/10.5772/intechopen.93709*

changes, have been proposed as the key mechanisms used by turfgrass to enhance survival under drought [37]. There is a series of morphology changes in perennial ryegrass under drought stress. Drought stress reduced the turf quality (TQ ), number of live tillers and dry-matter yield [38–40]. Moreover, drought significantly enhanced root to shoot ratio (R/S) in perennial ryegrass to an less extents, depending on the intensity, the reason may be that perennial ryegrass in drought stress develop a large R/S to maintain water and nutrient uptake [39]. The leaves of perennial ryegrass under drought stress were also dramatically different from that of nonstressed perennial ryegrass, for example, under drought stress, the diurnal variation in the rate of leaf extension was smaller but the leaves tended to grow faster at night compared to normal irrigation controls; however, water stress ultimately reduced the rate of leaf extension and leaf area in perennial ryegrass [40]. Furthermore, the leaves' epidermis of perennial ryegrass under drought reduced the stomatal size and increased the numbers per unit leaf area. Drought also resulted deeper ridging on leaf ad-axial surface, smaller epidermal cells and bigger ridge angle [40]. Under drought stress, leave stomata of perennial ryegrass began to close to reduce their evapotranspiration rate (ET), at leaf water potentials below—13 bars [40].

Drought stress causes significant physiological changes, including photosynthesis, osmotic adjustment substances, proteins, and antioxidant metabolism, in perennial ryegrass. For instance, the content of leaf total nitrogen and leaf relative water content (RWC) were tested to decrease, on the contrary, antioxidant activity including ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), amino acids such as aspartic acid, threonine, serine, glutamic acid, abscisic acid (ABA) concentration, and proline content increased under drought stress [41]. Photosynthesis is the primary process controlling plant growth and adaption to drought stress [42]. The canopy photosynthesis of perennial ryegrass at saturating light intensity was reduced by about half in the stressed field swards and by more than 80% in the stressed simulated swards [38]. Drought stress inhibits photosynthesis, which may be the result of low CO2 availability caused by stomatal closure and/or the inhibition of photochemical reactions and carbon assimilation metabolism [43]. In addition to the photosynthesis, starchis also considered as a buffer for imbalance between acquisition by photosynthesis and C-sink activities such as growth and respiration resulted from drought, also stress due to the excessive use of inorganic fertilizer [44]. However, use of green manure also has risk of xenobiotic contamination [45–47], and the soluble sugars, including sucrose, fructose and glucose, are involved in multiple physiological functions such as respiration, turgor maintenance, signaling and defense. Under drought conditions, starch of perennial ryegrass significantly decreased in shoots, but did not change in roots, which indicated that perennial ryegrass in drought condition preferentially allocates carbon not only to root growth, but also to root storage, while soluble sugars were enhanced in both shoots and roots. Accumulation of soluble sugars has been widely reported for plants upon water stress as a means to provide osmotic protection [39], which suggested that increasing of soluble sugars was benefit to plants to maintain growth and active metabolic activities under water deficit.

It is generally accepted that there is a noticeable genotypic variation in perennial ryegrass for drought stress responses. The research showed that one self-pollinating genotype "S10" showed higher RWC, shoot dry weight (SDW), proline, ABA, nitrogen and amino acid contents, and antioxidant enzymes activities in comparison with two commercial genotypes of "Vigor" and "Speedy" [41]. Proteins involved in carbon and energy metabolism, photosynthesis, tricarboxylic acid cycle (TCA) cycle, redox, and transport categories were upregulated in the two commercial genotypes of "Vigo" and "Speedy," while the protein profile of the "S10" changed

*Abiotic Stress in Plants*

and tillering ability. It is also widely used as nutritive forage and pasture grass for animals around the world [6–8]. Moreover, numerous perennial ryegrass genotypes

the maintenance of high-quality turf under limited resource availability.

perennial ryegrass under abiotic stress will be discussed in this chapter.

**2.1 Responses of drought stress in perennial ryegrass**

Abiotic stresses are major environmental conditions that reduce plant growth, productivity, and quality. Plants have evolved mechanisms to perceive these environmental challenges, transmit the stress signals within cells as well as between cells and tissues, and make appropriate adjustments in their growth and development for survive and reproduce [26–29]. The morphological and physiological changes of

Growth and development processes are inhibited when plant is exposed to drought

stress [30–36]. Morphological adjustments, such as biomass allocation and leave

In fields, the growth and development process of plants needs to counteract various environmental stresses such as salinity, drought, cold, heat, and heavy metal [11–13]. Harsh environmental conditions may result in growth inhibition, cell structure damage, and metabolic dysfunction [14–20]. Moreover, stresses will further be intensified for the potential impact of climate change in future. Thus, maintaining proper growth of turfgrass with minimal inputs under abiotic stress conditions is a great challenge for turfgrass industry. This challenge could be addressed through improving the stress tolerance of turfgrass [14, 21]. Understanding morphological and physiological mechanisms of turfgrass adaptation to various abiotic stresses is a key step for the development of stress-tolerant ability and cost-effective and efficient management practices [13]. Morphophysiological mechanisms of turfgrass in abiotic stresses tolerance involve phenotypic changes, multiple physiological and biochemical response, and complex metabolic processes, such as water and nutrient relations, carbohydrate metabolism, protein metabolism, hormone metabolism, as well as antioxidant defenses [22, 23]. Current studies on morphophysiological mechanism controlling turfgrass adaptations to various growth conditions have provided important information for production of abiotic stress-tolerant germplasms and the further understanding of regulation mechanism of turfgrass response to abiotic stresses [13, 24, 25]. However, the mechanisms of the adaptive responses are integrated but are not necessarily the same [14]; thus, studies on how perennial ryegrass adapts to stress conditions will become more important with the increasing pressure of utilizing both ecological and economical strategies in the turf management. Furthermore, insights into mechanisms of stress resistance in perennial ryegrass will aid in identifying important characteristics for selecting the criteria of improving stress tolerance and will ultimately lead to better selection of new cultivars adapted to adverse environments. This chapter, therefore, focuses on an extensive overview of the current understanding of changes in physiology and growth/development of perennial ryegrass under various abiotic stresses. In addition, strategies for improving the stress tolerance of perennial ryegrass are also presented. This review can contribute to the better understanding of the mechanisms of perennial ryegrass response to environmental stresses and can provide valuable information for improving resistance characteristics of perennial ryegrass by breeding. Moreover, enhancing our understanding of physiological effects of abiotic stresses can provide guidelines for the practical management strategies of

and hybrids are now released by commercial utilities [9, 10].

**354**

**2. Abiotic stresses**

slightly under drought stress, and the reason may be that self-pollination in the genetic background of the "S10" genotype may have a lower variation in response to drought stress conditions [41]. Additionally, other research indicated that tetraploid perennial ryegrass exhibited a greater biomass under severe drought, whereas diploids had a greater biomass under the current rainfall [48, 49]. Moreover, tetraploid perennial ryegrass populations were able to develop more shoot and root dry matter than diploid populations in following the application of drought stress [50].

The above researches showed that drought stress caused significantly physiological and morphological changes in perennial ryegrass (**Table 1**) [55, 56]. Thus, the growth of perennial ryegrass is severely restricted by soil water deficits [57]. Increasing drought tolerance of perennial ryegrass via strategies is importance for both water conservation and maintaining growth in water limiting environments. For example, the grass-Epichloë endophytic improved water utilization and drought tolerance in perennial ryegrass [58]. Moreover, arbuscular mycorrhizal fungi (AMF) + Epichloë treatments increased phosphorus (P) uptake, net photosynthetic rate (Pn), root activity, soluble sugar concentration, peroxidase (POD) activity, and decreased malonyldialdehyde (MDA) concentration in perennial ryegrass under drought stress, the reason may be that Plant-AMF-Epichloë symbiosis alleviated the damage caused by drought stress by promoting P uptake, photosynthesis, and the accumulation of osmoregulatory substances [59]. Additionally, application of plant growth regulators (PGRs) have been reported to be a promising way of reducing drought stress impacts [60]. The study manifested that trinexapac ethyl (TE) treatment increased chlorophyll content, proline content, the RWC, soluble sugar content, antioxidant enzymes activities, decreased MDA and hydrogen peroxide (H2O2) contents in perennial ryegrass under drought stress, while Paclobutrazol (PAC)- and ABA-treated perennial ryegrasses were all effective in mitigating physiological damages resulting from drought stress [52]. Furthermore, overexpression of some drought-related genes has been shown to effectively improve drought tolerance of plants [61]. According to Patel et al. [53], overexpression of *LpHUB1* gene conferred drought tolerance in perennial ryegrass.

#### **2.2 Responses of temperature stress in perennial ryegrass**

Perennial ryegrass can grow throughout the year, and the major constraint on growth is temperature [51, 62]. Perennial ryegrass has an optimal growth temperature of about 20°C, and it is sensitive to high (30–40°C) and low (−20 to 0°C) temperatures [63, 64]. Common perennial ryegrass germinates quickly and can be used as a temporary ground cover while the slower growing bluegrass plants take


**357**

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass…*

ryegrass will be beneficial to improve heat or freezing tolerance [86].

hold in cool temperate region. In warm climates, it is used as an overseed to maintain winter green in the lawn after the warm season grasses go dormant. However, populations of perennial ryegrass will not survive the summer heat. Severe heat stress (40/35°C day/night) caused significant physiological damages, including declining in TQ, RWC, CAT activity, and enhancing in electrolyte leakage (EL) of leaves and MDA content, in perennial ryegrass [65]. Moreover, heat stress decreased plant height (HT), leaf fresh weight (LFW) and leaf fresh dry (LFD), and increased cytokinin and auxin at 35/30°C (day/night) of temperature [66]. Moreover, low temperature is one of the main factors that limit the persistence of perennial ryegrassdominated grasslands in northern regions. Cold stress decreased TQ, regrowth, dry weight, and tiller density in perennial ryegrass when the winters were mild with short (2–6 weeks) periods of lower than −10°C temperatures and no permanent snow cover [67]. Furthermore, cold stress decreased RWC and increase EL in leaves and roots when perennial ryegrass was exposed to −15 or −25°C [68]. To resolve these problems and maintain high visual quality of perennial ryegrass through the year, it is important to found new cultivars to adapt to temperature stress. Variations of heat- or cold- resistance were also found among different perennial ryegrass cultivars. Thus, selection cold- or heat-tolerant cultivars during perennial ryegrass genotypes can be an effective method for temperature tolerance improvement in perennial ryegrass. The research tested the heat tolerance of 58 cultivars collected from seed companies and research centers in U.S.A., New Zealand, and Europe, the result showed that distinct heat tolerance was found among the cultivars at all the temperature regimes, and the least and most tolerant cultivars were "JPR005" and "JPR178," respectively [69]. The other research indicated that changes of morphology and physiology were different for heat-tolerant accession "PI265351" and sensitive accession "PI225825" [66]. Similarly, the heat-tolerant populations of perennial grass showed significantly lower degree damage in efficiency of photosystem II and cell membrane stability than the sensitive ones at different levels of stress [70]. Additionally, the study showed that 21 accessions sampled from a larger set of 300 accessions with known winter hardiness, the result showed that the degree of semilethal temperature in 21 ryegrass varieties varies from −10.31 to −13.95°C, with 3 accessions possessing significantly greater freezing tolerance than the most freezetolerant check "NK200" [71]. Moreover, tetraploid genotypes of perennial ryegrass demonstrated higher tolerance to cold stress conditions, better spring growth, and regrowth after cuts, and higher dry matter yield compared to diploid genotypes [67]. The studies indicate that temperature stress caused the morphological and physiological damage in plant, and the response of genotypes to temperature stress was different [72–80]. Therefore, founding some strategies which could improve cold- or heat-tolerant of perennial ryegrass is important. It was also reported that 24-epibrassinolide promoted carbohydrates accumulation in crowns of perennial ryegrass during cold acclimation by regulation of gene expression and enzyme activities, and which resulted in increased frost tolerance [81]. Moreover, drought preconditioning increased in crown fructans, proline, and total soluble protein content for "Buccaneer" and "Sunkissed" during cold acclimation, which suggested a synergistic effect between drought exposure and low temperature, and drought preconditioning resulted in an improvement in freezing tolerance of perennial ryegrass [82]. Additionally, previous studies have shown that the enzyme activity level and gene expression of antioxidants are associated with cold and heat tolerance in a cool-season perennial grass species [83, 84]. For instance, *LpHOX21* was positively associated with heat tolerance of perennial ryegrass [85]. Similarly, P450 gene (*LpCYP72A161*) showed remarkable upregulation in perennial ryegrass under heat and cold treatment. Therefore, transferring key genes into perennial

*DOI: http://dx.doi.org/10.5772/intechopen.93709*

#### **Table 1.**

*Morphophysiological response of perennial ryegrass under drought stress.*

#### *Plant Growth and Morphophysiological Modifications in Perennial Ryegrass… DOI: http://dx.doi.org/10.5772/intechopen.93709*

hold in cool temperate region. In warm climates, it is used as an overseed to maintain winter green in the lawn after the warm season grasses go dormant. However, populations of perennial ryegrass will not survive the summer heat. Severe heat stress (40/35°C day/night) caused significant physiological damages, including declining in TQ, RWC, CAT activity, and enhancing in electrolyte leakage (EL) of leaves and MDA content, in perennial ryegrass [65]. Moreover, heat stress decreased plant height (HT), leaf fresh weight (LFW) and leaf fresh dry (LFD), and increased cytokinin and auxin at 35/30°C (day/night) of temperature [66]. Moreover, low temperature is one of the main factors that limit the persistence of perennial ryegrassdominated grasslands in northern regions. Cold stress decreased TQ, regrowth, dry weight, and tiller density in perennial ryegrass when the winters were mild with short (2–6 weeks) periods of lower than −10°C temperatures and no permanent snow cover [67]. Furthermore, cold stress decreased RWC and increase EL in leaves and roots when perennial ryegrass was exposed to −15 or −25°C [68]. To resolve these problems and maintain high visual quality of perennial ryegrass through the year, it is important to found new cultivars to adapt to temperature stress. Variations of heat- or cold- resistance were also found among different perennial ryegrass cultivars. Thus, selection cold- or heat-tolerant cultivars during perennial ryegrass genotypes can be an effective method for temperature tolerance improvement in perennial ryegrass. The research tested the heat tolerance of 58 cultivars collected from seed companies and research centers in U.S.A., New Zealand, and Europe, the result showed that distinct heat tolerance was found among the cultivars at all the temperature regimes, and the least and most tolerant cultivars were "JPR005" and "JPR178," respectively [69]. The other research indicated that changes of morphology and physiology were different for heat-tolerant accession "PI265351" and sensitive accession "PI225825" [66]. Similarly, the heat-tolerant populations of perennial grass showed significantly lower degree damage in efficiency of photosystem II and cell membrane stability than the sensitive ones at different levels of stress [70]. Additionally, the study showed that 21 accessions sampled from a larger set of 300 accessions with known winter hardiness, the result showed that the degree of semilethal temperature in 21 ryegrass varieties varies from −10.31 to −13.95°C, with 3 accessions possessing significantly greater freezing tolerance than the most freezetolerant check "NK200" [71]. Moreover, tetraploid genotypes of perennial ryegrass demonstrated higher tolerance to cold stress conditions, better spring growth, and regrowth after cuts, and higher dry matter yield compared to diploid genotypes [67].

The studies indicate that temperature stress caused the morphological and physiological damage in plant, and the response of genotypes to temperature stress was different [72–80]. Therefore, founding some strategies which could improve cold- or heat-tolerant of perennial ryegrass is important. It was also reported that 24-epibrassinolide promoted carbohydrates accumulation in crowns of perennial ryegrass during cold acclimation by regulation of gene expression and enzyme activities, and which resulted in increased frost tolerance [81]. Moreover, drought preconditioning increased in crown fructans, proline, and total soluble protein content for "Buccaneer" and "Sunkissed" during cold acclimation, which suggested a synergistic effect between drought exposure and low temperature, and drought preconditioning resulted in an improvement in freezing tolerance of perennial ryegrass [82]. Additionally, previous studies have shown that the enzyme activity level and gene expression of antioxidants are associated with cold and heat tolerance in a cool-season perennial grass species [83, 84]. For instance, *LpHOX21* was positively associated with heat tolerance of perennial ryegrass [85]. Similarly, P450 gene (*LpCYP72A161*) showed remarkable upregulation in perennial ryegrass under heat and cold treatment. Therefore, transferring key genes into perennial ryegrass will be beneficial to improve heat or freezing tolerance [86].

*Abiotic Stress in Plants*

slightly under drought stress, and the reason may be that self-pollination in the genetic background of the "S10" genotype may have a lower variation in response to drought stress conditions [41]. Additionally, other research indicated that tetraploid perennial ryegrass exhibited a greater biomass under severe drought, whereas diploids had a greater biomass under the current rainfall [48, 49]. Moreover, tetraploid perennial ryegrass populations were able to develop more shoot and root dry matter

than diploid populations in following the application of drought stress [50].

**2.2 Responses of temperature stress in perennial ryegrass**

**Morphological responses Physiological responses Strategies**

substances

[39, 41, 51]

*Morphophysiological response of perennial ryegrass under drought stress.*

• Decline biomass

• Decline photosynthetic rate • Increased osmotic adjustment • Application of plant growth regulators (PGRs)

from different cultivars • Using endophytes

• Selected drought resistance cultivars

• Using transgenic technology [52–54]

• Increased antioxidant activity • Increased amino acid content

Perennial ryegrass can grow throughout the year, and the major constraint on growth is temperature [51, 62]. Perennial ryegrass has an optimal growth temperature of about 20°C, and it is sensitive to high (30–40°C) and low (−20 to 0°C) temperatures [63, 64]. Common perennial ryegrass germinates quickly and can be used as a temporary ground cover while the slower growing bluegrass plants take

The above researches showed that drought stress caused significantly physiological and morphological changes in perennial ryegrass (**Table 1**) [55, 56]. Thus, the growth of perennial ryegrass is severely restricted by soil water deficits [57]. Increasing drought tolerance of perennial ryegrass via strategies is importance for both water conservation and maintaining growth in water limiting environments. For example, the grass-Epichloë endophytic improved water utilization and drought tolerance in perennial ryegrass [58]. Moreover, arbuscular mycorrhizal fungi (AMF) + Epichloë treatments increased phosphorus (P) uptake, net photosynthetic rate (Pn), root activity, soluble sugar concentration, peroxidase (POD) activity, and decreased malonyldialdehyde (MDA) concentration in perennial ryegrass under drought stress, the reason may be that Plant-AMF-Epichloë symbiosis alleviated the damage caused by drought stress by promoting P uptake, photosynthesis, and the accumulation of osmoregulatory substances [59]. Additionally, application of plant growth regulators (PGRs) have been reported to be a promising way of reducing drought stress impacts [60]. The study manifested that trinexapac ethyl (TE) treatment increased chlorophyll content, proline content, the RWC, soluble sugar content, antioxidant enzymes activities, decreased MDA and hydrogen peroxide (H2O2) contents in perennial ryegrass under drought stress, while Paclobutrazol (PAC)- and ABA-treated perennial ryegrasses were all effective in mitigating physiological damages resulting from drought stress [52]. Furthermore, overexpression of some drought-related genes has been shown to effectively improve drought tolerance of plants [61]. According to Patel et al. [53], overexpression of *LpHUB1* gene conferred drought tolerance in perennial ryegrass.

**356**

**Table 1.**

• Decreased turf quality • Enhanced R/S • Decreased leaf area • Reduce the number of live

• Had smaller stomata and epidermal cells • Had bigger ridge angle • Controlled stomatal opening [38–40]

tillers

#### **2.3 Responses of salt stress in perennial ryegrass**

Salinity stress has become a more significant problem in turfgrass management in many areas [13]. Responses of plants to salinity stress occur mainly through two distinct phases over time: osmotic-changing and ion specific phases [87–89]. Like other turfgrasses, salt stress caused morphology, physiology, molecular changes in growth and development of perennial ryegrass, such as TQ LFW, LED, and RWC of perennial ryegrass decreasing after exposure to salinity [89, 90]. The alterations of morphological characteristics of turfgrass under salt stress are derived from the changes of physiological traits such as cell membrane stability [14]. It was reported that MDA content and EL enhanced by NaCl concentration in perennial ryegrass [54]. Simultaneously, superoxide radical (O2−), H2O2, and singlet oxygen (O2) concentration increased observably in perennial ryegrass after salt stress treatment [54, 91]. To scavenge reactive oxygen species (ROS), salt-stressed leaves of perennial ryegrass exhibited greater activities of SOD, APX, and CAT at the initial stage of salt stress, but lower levels of enzyme with the extension of salt stress [89]. Salt stress also negatively affected on the total chlorophyll (Chl), Chl a and Chl b, in perennial ryegrass [89], which showed that salt stress induced Chl decomposition in leaves. Moreover, a further research of PSII changes in perennial ryegrass discovered that quantum yields, efficiencies, and energy fluxes were impacted after salt stress treatment [92, 93]. Additionally, a vast amount of Na+ accumulated in plants could induce ionic imbalance in the cells. It was reported that Na<sup>+</sup> concentration accumulated rapidly and other ion concentrations including K<sup>+</sup> , Ca2+ and Mg2+ were decreased in response to salt stress in perennial ryegrass [89].

Salt stress causes dramatically changes in morphology and physiology of perennial ryegrass as showed above and summaries in **Figure 1**. However, these responses varied greatly among different genotypes. The research compared the salt tolerance in 10 accessions of perennial ryegrass, and determined that "PI275660"

**359**

ryegrass [99, 111, 112].

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass…*

and "BrightStar" showed the best tolerance to salt stress, while "PI231595" and "PI251141" were the most sensitive accessions [5]. The other research reported that the effect on parameters of photosynthetic efficiency in perennial ryegrass "Roadrunner" was less than that in "Nira" under salt stress condition [6]. Moreover, the highest salt tolerance accessions were from the European group, wild accessions and exhibited more variation in functional traits and salt tolerance than commercial cultivars [90]. Some other strategies can also improve the salt-tolerance in perennial ryegrass. Salt-tolerant transgenic perennial ryegrass could be obtained by *Agrobacterium tumefaciens*-mediated transformation of the vacuolar Na+

antiporter gene [94]. Additionally, exogenous cytokinin applications alleviated salt-induced leaf senescence in perennial ryegrass [8]. Furthermore, salt tolerance of perennial ryegrass can increase by a novel bacterium strain from the rhizosphere

The continuing industrialization has led to extensive environmental problems worldwide [96–98]. Heavy metals produced from industry are released to soil. Thus, high accumulation of heavy metal in soil can induce environmental stress on plants [14]. Research on the response of perennial ryegrass to heavy metal stress has also progressed in recent years. It has been proved that heavy metals can induce damage and affect metabolic processes in perennial ryegrass [98–100]. For example, perennial ryegrass had characters in yield reduction and visible symptoms of phytotoxicity under cadmium (Cd) and zinc (Zn) stress [98]. Moreover, the cellular membrane system was damaged because of elevated MDA and EL contents when perennial ryegrass was exposed to salt condition [101]. According to studies, a dramatic inhibition of root and shoot growth was detected in perennial ryegrass after heavy metals treatment [101–103]. Moreover, the composition of the leaves of perennial ryegrass, including apparently opposite effects on the calcium (Ca), potassium (K) and P levels, was changed under the aluminum (Al) stress [104]. Additionally, ROS bursts occurred in perennial ryegrass under heavy mental stress conditions. For instance, H2O2 and O2− were significantly accumulated in perennial ryegrass under Cd stress [105]. Hence, the protection mechanisms in perennial ryegrass such as the antioxidant system were triggered under heavy stress, resulting in the increase of SOD, CAT, and POD activities and their corresponding genes [106]. Moreover, content of fructan, sugar, and starch showed an increasing trend in perennial ryegrass after heavy metal stress [98]. However, certain concentrations of heavy metal were beneficial for the growth of perennial ryegrass [107]. Heavy metal stresses not only induce physiological damage, but also inhibit germination and growth of perennial ryegrass [108]. To improve the heavy metal stress tolerance of perennial ryegrass, several investigations were conducted in recent years. It was reported that signal messengers such as nitricoxide (NO) and glycine betaine (GB) play crucial roles in alleviating Cd and Cu-induced damages in perennial ryegrass [109, 110]. Moreover, the exogenous P was testified to improve the Cd tolerance of perennial ryegrass, the reason may be that exogenous P facilitates chelation-mediated Cd detoxification processes [105]. Similarly, a high dose of P amendment alleviated Mn-toxicity in Mn-sensitive genotype in perennial ryegrass [102]. Furthermore, the addition of biochar to a contaminated mine soil improved the nutrient status of this mine soil and contributed to a better establishment of perennial ryegrass [100]. Additionally, AMF enhance both absorption and stabilization of Cd by perennial ryegrass in a Cd-contaminated acidic soil [96], and ethylene diamine tetra acetate (EDTA) enhanced phytoremediation of heavy metals from municipal waste compost and sludge soil by perennial

of a desert shrub *Haloxylon ammodendron* induced [95].

**2.4 Responses of heavy metals stress in perennial ryegrass**

/H+

*DOI: http://dx.doi.org/10.5772/intechopen.93709*

*Morphophysiological response and strategies for salt stress in perennial ryegrass.*

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass… DOI: http://dx.doi.org/10.5772/intechopen.93709*

and "BrightStar" showed the best tolerance to salt stress, while "PI231595" and "PI251141" were the most sensitive accessions [5]. The other research reported that the effect on parameters of photosynthetic efficiency in perennial ryegrass "Roadrunner" was less than that in "Nira" under salt stress condition [6]. Moreover, the highest salt tolerance accessions were from the European group, wild accessions and exhibited more variation in functional traits and salt tolerance than commercial cultivars [90]. Some other strategies can also improve the salt-tolerance in perennial ryegrass. Salt-tolerant transgenic perennial ryegrass could be obtained by *Agrobacterium tumefaciens*-mediated transformation of the vacuolar Na<sup>+</sup> /H+ antiporter gene [94]. Additionally, exogenous cytokinin applications alleviated salt-induced leaf senescence in perennial ryegrass [8]. Furthermore, salt tolerance of perennial ryegrass can increase by a novel bacterium strain from the rhizosphere of a desert shrub *Haloxylon ammodendron* induced [95].

#### **2.4 Responses of heavy metals stress in perennial ryegrass**

The continuing industrialization has led to extensive environmental problems worldwide [96–98]. Heavy metals produced from industry are released to soil. Thus, high accumulation of heavy metal in soil can induce environmental stress on plants [14]. Research on the response of perennial ryegrass to heavy metal stress has also progressed in recent years. It has been proved that heavy metals can induce damage and affect metabolic processes in perennial ryegrass [98–100]. For example, perennial ryegrass had characters in yield reduction and visible symptoms of phytotoxicity under cadmium (Cd) and zinc (Zn) stress [98]. Moreover, the cellular membrane system was damaged because of elevated MDA and EL contents when perennial ryegrass was exposed to salt condition [101]. According to studies, a dramatic inhibition of root and shoot growth was detected in perennial ryegrass after heavy metals treatment [101–103]. Moreover, the composition of the leaves of perennial ryegrass, including apparently opposite effects on the calcium (Ca), potassium (K) and P levels, was changed under the aluminum (Al) stress [104]. Additionally, ROS bursts occurred in perennial ryegrass under heavy mental stress conditions. For instance, H2O2 and O2− were significantly accumulated in perennial ryegrass under Cd stress [105]. Hence, the protection mechanisms in perennial ryegrass such as the antioxidant system were triggered under heavy stress, resulting in the increase of SOD, CAT, and POD activities and their corresponding genes [106]. Moreover, content of fructan, sugar, and starch showed an increasing trend in perennial ryegrass after heavy metal stress [98]. However, certain concentrations of heavy metal were beneficial for the growth of perennial ryegrass [107]. Heavy metal stresses not only induce physiological damage, but also inhibit germination and growth of perennial ryegrass [108].

To improve the heavy metal stress tolerance of perennial ryegrass, several investigations were conducted in recent years. It was reported that signal messengers such as nitricoxide (NO) and glycine betaine (GB) play crucial roles in alleviating Cd and Cu-induced damages in perennial ryegrass [109, 110]. Moreover, the exogenous P was testified to improve the Cd tolerance of perennial ryegrass, the reason may be that exogenous P facilitates chelation-mediated Cd detoxification processes [105]. Similarly, a high dose of P amendment alleviated Mn-toxicity in Mn-sensitive genotype in perennial ryegrass [102]. Furthermore, the addition of biochar to a contaminated mine soil improved the nutrient status of this mine soil and contributed to a better establishment of perennial ryegrass [100]. Additionally, AMF enhance both absorption and stabilization of Cd by perennial ryegrass in a Cd-contaminated acidic soil [96], and ethylene diamine tetra acetate (EDTA) enhanced phytoremediation of heavy metals from municipal waste compost and sludge soil by perennial ryegrass [99, 111, 112].

*Abiotic Stress in Plants*

**2.3 Responses of salt stress in perennial ryegrass**

stress treatment [92, 93]. Additionally, a vast amount of Na+

could induce ionic imbalance in the cells. It was reported that Na<sup>+</sup>

Salt stress causes dramatically changes in morphology and physiology of perennial ryegrass as showed above and summaries in **Figure 1**. However, these responses varied greatly among different genotypes. The research compared the salt tolerance in 10 accessions of perennial ryegrass, and determined that "PI275660"

accumulated rapidly and other ion concentrations including K<sup>+</sup>

decreased in response to salt stress in perennial ryegrass [89].

*Morphophysiological response and strategies for salt stress in perennial ryegrass.*

Salinity stress has become a more significant problem in turfgrass management in many areas [13]. Responses of plants to salinity stress occur mainly through two distinct phases over time: osmotic-changing and ion specific phases [87–89]. Like other turfgrasses, salt stress caused morphology, physiology, molecular changes in growth and development of perennial ryegrass, such as TQ LFW, LED, and RWC of perennial ryegrass decreasing after exposure to salinity [89, 90]. The alterations of morphological characteristics of turfgrass under salt stress are derived from the changes of physiological traits such as cell membrane stability [14]. It was reported that MDA content and EL enhanced by NaCl concentration in perennial ryegrass [54]. Simultaneously, superoxide radical (O2−), H2O2, and singlet oxygen (O2) concentration increased observably in perennial ryegrass after salt stress treatment [54, 91]. To scavenge reactive oxygen species (ROS), salt-stressed leaves of perennial ryegrass exhibited greater activities of SOD, APX, and CAT at the initial stage of salt stress, but lower levels of enzyme with the extension of salt stress [89]. Salt stress also negatively affected on the total chlorophyll (Chl), Chl a and Chl b, in perennial ryegrass [89], which showed that salt stress induced Chl decomposition in leaves. Moreover, a further research of PSII changes in perennial ryegrass discovered that quantum yields, efficiencies, and energy fluxes were impacted after salt

accumulated in plants

concentration

, Ca2+ and Mg2+ were

**358**

**Figure 1.**

#### **3. Conclusions and future research perspectives**

Significant progress has been made in the understanding of morphological and physiological mechanisms associated with perennial ryegrass tolerance to drought, salinity, temperature, and heavy mental stresses. Harsh stress conditions inhibit the growth and development and decrease TQ, root length, and dry weight in perennial ryegrass. Moreover, physiological response to abiotic stress in perennial ryegrass displays changes of the cell membrane, photosystem, metabolites, and antioxidant system. The contents of MDA and EL are increased, while Chl content and photosynthesis are decreased under stress conditions. To regulate the osmotic potential of the cell after stress treatment, some metabolites such as proline, soluble sugars, and proteins accumulate. Meanwhile, antioxidant enzymes' activities increase in perennial ryegrass for scavenging ROS. Perennial ryegrass has protective responses against unfavorable conditions, but there is a threshold to these physiological changes. To understand the response to abiotic stress and resistance attributes in perennial ryegrass will be beneficial to breeding in future.

For improving the stress tolerance of perennial ryegrass, some practical strategies are exploited currently, such as application of phytohormones, endophytes, and chemical compounds. Further research on increasing perennial ryegrass stress tolerance should pay more attention to transgenic technology to identify effective genes for modifying stress-tolerance ability.

#### **Author details**

Fuchun Xie1 , Rahul Datta2 and Dong Qin1 \*

1 College of Horticulture and Landscape Architecture, Northeast Agricultural University, Harbin, China

2 Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of AgriSciences, Mendel University in Brno, Brno, Czech Republic

\*Address all correspondence to: dongq9876@126.com

© 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.

**361**

10.1093/jxb/ert018

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass…*

[7] Yu X, Pijut PM, Byrne S, Asp T, Bai G, Jiang Y. Candidate gene

[8] Ma X, Zhang J, Huang B. Cytokinin-mitigation of salt-

envexpbot.2016.01.002

induced leaf senescence in perennial ryegrass involving the activation of antioxidant systems and ionic balance. Environmental and Experimental Botany. 2016;**125**:1-11. DOI: 10.1016/j.

[9] Dabrowski P, Pawluśkiewicz B, Kalaji HM, Baczewska AH. The effect of light availability on leaf area index, biomass production and plant species composition of park grasslands in Warsaw. Plant, Soil and Environment. 2013;**59**:543-548.

DOI: 10.17221/140/2013-PSE

[10] Dabrowski P, Pawluśkiewicz B, Baczewska AH, Oglecki P, Kalaji H. Chlorophyll a fluorescence of perennial ryegrass (*Lolium perenne* L.) varieties under long term exposure to shade. Zemdirbyste-Agriculture. 2015;**102**: 305-312. DOI: 10.13080/z-a.2015.102.039

[11] Shah S, Li X, Chen YJ, Zhang L, Fahad S, Hussain S, et al. Silicon application increases drought tolerance of Kentucky bluegrass by improving plant water relations and morphophysiological functions. The Scientific World Journal. 2014.

DOI: 10.1155/2014/368694

[12] Muhammad Z, Abdul MK,

Shahen S, et al. Performance of *Aeluropus lagopoides* (mangrove grass) ecotypes, a potential turfgrass, under high saline conditions. Environmental Science and Pollution Research. 2019. DOI: 10.1007/s11356-019-04838-3

Abdul MS, Kenneth BM, Muhammad S,

association mapping for winter survival and spring regrowth in perennial ryegrass. Plant Science. 2015;**235**:37-45. DOI: 10.1016/j.plantsci.2015.03.003

*DOI: http://dx.doi.org/10.5772/intechopen.93709*

[2] Hafiz MH, Muhammad A, Farhat A, Hafiz FB, Saeed AQ, Muhammad M, et al. Environmental factors affecting the frequency of road traffic accidents: A case study of sub-urban area of Pakistan. Environmental Science and Pollution Research. 2019. DOI: 10.1007/

[3] Sajjad H, Muhammad M, Ashfaq A, Waseem A, Hafiz MH, Mazhar A, et al. Using GIS tools to detect the land use/land cover changes during forty years in Lodhran district of Pakistan. Environmental Science and Pollution Research. 2019. DOI: 10.1007/

[4] Adnan M, Zahir S, Fahad S, Arif M, Mukhtar A, Imtiaz AK, et al. Phosphate-

antagonistic effect of soil calcification on bioavailability of phosphorus in alkaline soils. Scientific Reports. 2018;**8**:4339. DOI: 10.1038/s41598-018-22653-7

[5] Tang J, Camberato JJ, Yu X, Luo N, Bian S, Jiang Y. Growth response, carbohydrate and ion accumulation of diverse perennial ryegrass accessions to increasing salinity. Scientia Horticulturae. 2013;**154**:73-81. DOI: 10.1016/j.scienta.2013.02.021

[6] Yu X, Bai G, Liu S, Luo N, Wang Y, Richmond DS, et al. Association of candidate genes with drought tolerance traits in diverse perennial ryegrass accessions. Journal of Experimental Botany. 2013;**64**:1537-1551. DOI:

solubilizing bacteria nullify the

[1] Dabrowski P, Kalaji MH, Baczewska AH, Pawluśkiewicz B, Mastalerczuk G, Borawska-Jarmulowicz B, et al. Delayed chlorophyll a fluorescence, MR 820, and gas exchange changes in perennial ryegrass under salt stress. Journal of Luminescence. 2017;**183**:322-333. DOI: 10.1016/j.jlumin.2016.11.031

s11356-019-04752-8

s11356-019-06072-3

**References**

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass… DOI: http://dx.doi.org/10.5772/intechopen.93709*

#### **References**

*Abiotic Stress in Plants*

**3. Conclusions and future research perspectives**

perennial ryegrass will be beneficial to breeding in future.

genes for modifying stress-tolerance ability.

Significant progress has been made in the understanding of morphological and physiological mechanisms associated with perennial ryegrass tolerance to drought, salinity, temperature, and heavy mental stresses. Harsh stress conditions inhibit the growth and development and decrease TQ, root length, and dry weight in perennial ryegrass. Moreover, physiological response to abiotic stress in perennial ryegrass displays changes of the cell membrane, photosystem, metabolites, and antioxidant system. The contents of MDA and EL are increased, while Chl content and photosynthesis are decreased under stress conditions. To regulate the osmotic potential of the cell after stress treatment, some metabolites such as proline, soluble sugars, and proteins accumulate. Meanwhile, antioxidant enzymes' activities increase in perennial ryegrass for scavenging ROS. Perennial ryegrass has protective responses against unfavorable conditions, but there is a threshold to these physiological changes. To understand the response to abiotic stress and resistance attributes in

For improving the stress tolerance of perennial ryegrass, some practical strategies are exploited currently, such as application of phytohormones, endophytes, and chemical compounds. Further research on increasing perennial ryegrass stress tolerance should pay more attention to transgenic technology to identify effective

**360**

**Author details**

University, Harbin, China

, Rahul Datta2

\*Address all correspondence to: dongq9876@126.com

provided the original work is properly cited.

and Dong Qin1

\*

1 College of Horticulture and Landscape Architecture, Northeast Agricultural

2 Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of AgriSciences, Mendel University in Brno, Brno, Czech Republic

© 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,

Fuchun Xie1

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plants. Plant Growth Regulation. 2020. DOI: 10.1007/s10725-020-00647-8

[20] Kamarn M, Wenwen C, Irshad A, Xiangping M, Xudong Z, Wennan S, et al. Effect of paclobutrazol, a potential growth regulator on stalk mechanical strength, lignin accumulation and its relation with lodging resistance of maize. Plant Growth Regulation. 2017;**84**:317- 332. DOI: 10.1007/s10725-017-0342-8

[21] Huang S, Jiang S, Liang J, Chen M, Shi Y. Current knowledge of bermudagrass responses to abiotic stresses. Breeding Science. 2019;**69**: 215-226. DOI: 10.1270/jsbbs.18164

[22] Saud S, Chen Y, Fahad S, Hussain S, Na L, Xin L, et al. Silicate application increases the photosynthesis and its associated metabolic activities in Kentucky bluegrass under drought stress and post-drought recovery. Environmental Science and Pollution Research. 2016;**23**(17):17647-17655. DOI: 10.1007/s11356-016-6957-x

[23] Chen Y, Pettersen T, Kvalbein A, Aamlid TS. Playing quality, growth rate, thatch accumulation and tolerance to moss and annual bluegrass invasion as influenced by irrigation strategies on red fescue putting greens. Journal of Agronomy and Crop Science. 2018;**204**:185-195. DOI: 10.1111/

[24] Saud S, Chen Y, Long B, Fahad S, Sadiq A. The different impact on the growth of cool season turf grass under the various conditions on salinity and drought stress. International Journal of Agricultural Science and Research.

[25] Saud S, Fahad S, Cui G, Chen Y, Anwar S. Determining nitrogen isotopes discrimination under drought stress on enzymatic activities, nitrogen isotope abundance and water contents of Kentucky bluegrass. Scientific

jac.12246

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Comparative physiological and

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[99] Li F, Qiu Y, Xu X, Yang F, Wang Z, Feng J, et al. EDTA-enhanced phytoremediation of heavy metals from sludge soil by Italian ryegrass (*Lolium perenne* L.). Ecotoxicology and Environmental Safety. 2020;**191**:110185. DOI: 10.1016/j.ecoenv.2020.110185

[100] Norini M, Thouin H, Miard F, Battaglia-Brunet F, Gautret P, Guégan R, et al. Mobility of Pb, Zn, Ba, As and Cd toward soil pore water and plants (willow and ryegrass) from a mine soil amended with biochar. Journal of Environmental Management. 2019;**232**:117-130. DOI: 10.1016/j.jenvman.2018.11.021

[101] Zhao S, Liu Q, Qi Y, Duo L. Responses of root growth and protective enzymes to copper stress in turfgrass. Acta Biologica Cracoviensia Series Botanica. 2010;**52**:7-11. DOI: 10.2478/ v10182-010-0017-5

[102] Berríos GA, Escobar AL, Alberdi MR, Nunes-Nesi A, Reyes-Díaz MM. Manganese toxicity amelioration by phosphorus supply in contrasting Mn resistant genotypes of ryegrass. Plant Physiology and Biochemistry. 2019;**144**:144-156. DOI: 10.1016/j.plaphy.2019.09.034

[103] Hu Y, Habibul N, Hu Y, Meng F, Zhang X, Sheng G. Mixture toxicity and uptake of 1-butyl-3-methylimidazolium bromide and cadmium co-contaminants in water by perennial ryegrass (*Lolium perenne* L.). Journal of Hazardous Materials. 2020;**386**:121972. DOI: 10.1016/j.jhazmat.2019.121972

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[105] Jia H, Hou D, Connor DO, Pan S, Zhu J, Bolan NS, et al. Exogenous

**369**

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass…*

[112] Zhao S, Lian F, Duo L. EDTAassisted phytoextraction of heavy metals by turfgrass from municipal solid waste compost using permeable barriers and associated potential leaching risk. Bioresource Technology. 2011;**102**:621-626. DOI: 10.1016/j.

biortech.2010.08.006

*DOI: http://dx.doi.org/10.5772/intechopen.93709*

Hazardous Materials. 2020;**389**:121849. DOI: 10.1016/j.jhazmat.2019.121849

expression in perennial ryegrass (*Lolium perenne* L.) under cadmium stress. Ecotoxicology. 2011;**20**:770-778. DOI:

phosphorus treatment facilitates chelation-mediated cadmium detoxification in perennial ryegrass (*Lolium perenne* L.). Journal of

[106] Luo H, Li H, Zhang X, Fu J. Antioxidant responses and gene

10.1007/s10646-011-0628-y

[107] Hua L, Wang Y, Wu W, McBride MB, Chen Y. Biomass and Cu and Zn uptake of two turfgrass species grown in sludge compost–soil mixtures. Water, Air, and Soil Pollution.

2008;**188**:225-234. DOI: 10.1007/

[108] Taghizadeh M, Solgi E. Impact of heavy metal stress on in vitro seed germination and seedling growth indices of two turfgrass species. Journal of Rangeland Science. 2017;**7**:

[109] Lou Y, Yang Y, Hu L, Liu H, Xu Q. Exogenous glycinebetaine alleviates the detrimental effect of Cd stress on perennial ryegrass. Ecotoxicology. 2015;**24**:1330-1340. DOI: 10.1007/

[110] Dong Y, Xu L, Wang Q, Fan Z, Kong J, Bai X. Effects of exogenous nitric oxide on photosynthesis, antioxidative ability, and mineral element contents of perennial ryegrass under copper stress. Journal of Plant Interactions. 2014;**9**:402-411. DOI: 10.1080/17429145.2013.845917

[111] Duo LA, Lian F, Zhao SL. Enhanced uptake of heavy metals in municipal solid waste compost by turfgrass following the application of EDTA. Environmental Monitoring and Assessment. 2010;**165**:377-387. DOI:

10.1007/s10661-009-0953-2

s11270-007-9539-1

s10646-015-1508-7

220-231

*Plant Growth and Morphophysiological Modifications in Perennial Ryegrass… DOI: http://dx.doi.org/10.5772/intechopen.93709*

phosphorus treatment facilitates chelation-mediated cadmium detoxification in perennial ryegrass (*Lolium perenne* L.). Journal of Hazardous Materials. 2020;**389**:121849. DOI: 10.1016/j.jhazmat.2019.121849

*Abiotic Stress in Plants*

[93] Li X, Han S, Wang G, Liu X, Amombo E, Xie Y, et al. The fungus *Aspergillus aculeatus* enhances salt-stress tolerance, metabolite accumulation, and improves forage quality in perennial ryegrass. Frontiers in Microbiology.

[99] Li F, Qiu Y, Xu X, Yang F,

Wang Z, Feng J, et al. EDTA-enhanced phytoremediation of heavy metals from sludge soil by Italian ryegrass (*Lolium perenne* L.). Ecotoxicology and Environmental Safety. 2020;**191**:110185. DOI: 10.1016/j.ecoenv.2020.110185

[100] Norini M, Thouin H, Miard F, Battaglia-Brunet F, Gautret P, Guégan R, et al. Mobility of Pb, Zn, Ba, As and Cd toward soil pore water and plants (willow and ryegrass) from a mine soil amended with biochar. Journal of Environmental Management. 2019;**232**:117-130. DOI:

10.1016/j.jenvman.2018.11.021

v10182-010-0017-5

[101] Zhao S, Liu Q, Qi Y, Duo L.

[102] Berríos GA, Escobar AL, Alberdi MR, Nunes-Nesi A, Reyes-Díaz MM. Manganese toxicity amelioration by phosphorus supply in contrasting Mn resistant genotypes of ryegrass. Plant Physiology and Biochemistry. 2019;**144**:144-156. DOI:

10.1016/j.plaphy.2019.09.034

[104] Bennet J, Stewart A. The aluminium response network in perennial ryegrass (*Lolium perenne*): II. Water fluxes and ion transport. South African Journal of Plant and Soil. 1999;**16**(1):1-9. DOI: 10.1080/02571862.1999.10634837

[105] Jia H, Hou D, Connor DO, Pan S, Zhu J, Bolan NS, et al. Exogenous

[103] Hu Y, Habibul N, Hu Y, Meng F, Zhang X, Sheng G. Mixture toxicity and uptake of 1-butyl-3-methylimidazolium bromide and cadmium co-contaminants in water by perennial ryegrass (*Lolium perenne* L.). Journal of Hazardous Materials. 2020;**386**:121972. DOI: 10.1016/j.jhazmat.2019.121972

Responses of root growth and protective enzymes to copper stress in turfgrass. Acta Biologica Cracoviensia Series Botanica. 2010;**52**:7-11. DOI: 10.2478/

2017;**8**:1664. DOI: 10.3389/

[94] Wu Y, Chen Q, Chen M, Chen J, Wang X. Salt-tolerant transgenic perennial ryegrass (*Lolium perenne* L.) obtained by *Agrobacterium tumefaciens*mediated transformation of the vacuolar

2005;**169**(1):65-73. DOI: 10.1016/j.

strain from the rhizosphere of a desert shrub *Haloxylon ammodendron*. International Journal of Molecular Sciences. 2018;**19**:469. DOI: 10.3390/

[95] He A, Niu S, Zhao Q, Li Y, Gou J, Gao H. Induced salt tolerance of

[96] Fahad S, Rehman A, Shahzad B, Tanveer M, Saud S, Kamran M, et al. Rice responses and tolerance to metal/metalloid toxicity. In:

Hasanuzzaman M, Fujita M, Nahar K, Biswas JK, editors. Advances in Rice Research for Abiotic Stress Tolerance. Cambridge, England: Woodhead Publ

Muhammad Y, Muhammad ZI, Abdul K, Fahad S, et al. Zinc biofortification in rice: Leveraging agriculture to moderate hidden hunger in developing countries. Archives of Agronomy and Soil Science. 2017;**64**:147-161. DOI: 10.1080/03650340.2017.1338343

perennial ryegrass by a novel bacterium

antiporter gene. Plant Science.

fmicb.2017.01664

plantsci.2005.02.030

ijms19020469

Ltd; 2019. pp. 299-312

[97] Qamar-uz Z, Zubair A,

[98] Frossard R, Stadelmann FX, Niederhauser J. Effects of different heavy metals on fructan, sugar and starch content of ryegrass. Journal of Plant Physiology. 1989;**134**:180-185. DOI: 10.1016/s0176-1617(89)80052-5

Na+ /H+

**368**

[106] Luo H, Li H, Zhang X, Fu J. Antioxidant responses and gene expression in perennial ryegrass (*Lolium perenne* L.) under cadmium stress. Ecotoxicology. 2011;**20**:770-778. DOI: 10.1007/s10646-011-0628-y

[107] Hua L, Wang Y, Wu W, McBride MB, Chen Y. Biomass and Cu and Zn uptake of two turfgrass species grown in sludge compost–soil mixtures. Water, Air, and Soil Pollution. 2008;**188**:225-234. DOI: 10.1007/ s11270-007-9539-1

[108] Taghizadeh M, Solgi E. Impact of heavy metal stress on in vitro seed germination and seedling growth indices of two turfgrass species. Journal of Rangeland Science. 2017;**7**: 220-231

[109] Lou Y, Yang Y, Hu L, Liu H, Xu Q. Exogenous glycinebetaine alleviates the detrimental effect of Cd stress on perennial ryegrass. Ecotoxicology. 2015;**24**:1330-1340. DOI: 10.1007/ s10646-015-1508-7

[110] Dong Y, Xu L, Wang Q, Fan Z, Kong J, Bai X. Effects of exogenous nitric oxide on photosynthesis, antioxidative ability, and mineral element contents of perennial ryegrass under copper stress. Journal of Plant Interactions. 2014;**9**:402-411. DOI: 10.1080/17429145.2013.845917

[111] Duo LA, Lian F, Zhao SL. Enhanced uptake of heavy metals in municipal solid waste compost by turfgrass following the application of EDTA. Environmental Monitoring and Assessment. 2010;**165**:377-387. DOI: 10.1007/s10661-009-0953-2

[112] Zhao S, Lian F, Duo L. EDTAassisted phytoextraction of heavy metals by turfgrass from municipal solid waste compost using permeable barriers and associated potential leaching risk. Bioresource Technology. 2011;**102**:621-626. DOI: 10.1016/j. biortech.2010.08.006

**371**

**Chapter 18**

**Abstract**

QTLs, rice, yield

**1. Introduction**

Rice Varieties

Advances in Developing Multigene

Abiotic and Biotic Stress-Tolerant

Increasing incidences of multiple abiotic stresses together with increasing population are the major constraints to attain the global food security. Rice, the major staple food crop is very much prone to various abiotic and biotic stresses, which can occur one at a time or two or more together in a single crop growing season and adversely affects the rice production and productivity. The devastating effect of multiple stresses on rice crop is much more erratic and complex leading to higher losses in the crop grain yield. The concurrent occurrence of multiple streeses can destroy rice production in many of the rainfed areas of South and Southeast-Asia. Genomics-assisted breeding strategies have been instrumental in introgression of various major effect QTLs/genes into rice mega varieties and have proven successful in achieving the desired level of tolerance/resistance to various abiotic stresses in diffferent crop species. Keeping the present scenario of changing climate in mind, the chapter discusses the recent past success in combining tolerance to two or more abiotic stresses in mega rice varieties applying genomicsassisted breeding and development of high-yielding climate resilient rice through stacking of multiple genes/QTLs, which can withstand in a cascade of multiple

**Keywords:** abiotic stress, biotic stress, genomic-assisted breeding, pyramiding,

Global warming and the changing climatic conditions lead to the concurrence of multiple abiotic and biotic stresses individually/or in combination [1, 2] thus adversely affecting the rice crop growth and yield [3]. The changing climate, more and more extreme weather events are increasing the probability of simultaneous multiple abiotic stresses, including extra pressure from biotic stresses. Abiotic and biotic stresses reported to have significant negative impact on rice crop survival, growth, development and yield in most parts of the world, especially the Asia and Africa [4, 5]. The abiotic stresses such as drought, salinity, cold, high temperature and heavy metals are known to influence the occurrence of biotic stresses [6–8]. The combined effect of multiple stresses may resulted the minor pests to become

*Nitika Sandhu, Shailesh Yadav and Arvind Kumar*

stresses occurring regularly in rainfed environments.

the potential threats in the coming future [1, 9, 10].

#### **Chapter 18**
