**2. Anatomical, morphological, and physiological changes of a red currant leaf due to drought and high temperature**

The study of the assimilation apparatus in red currants gives a complete picture of the plasticity of the genotype in relation to the ecological factors of the environment [11, 22–24]. The investigation of the anatomical and morphological features of red currant leaf structure showed that some morphological features, such as shape and venation, depend on the biological characteristics of the variety and the anatomical structure is more influenced by the growing conditions. During the periods with insufficient water supply, the leaf surface area decreased in all studied currant samples compared to optimal conditions. A positive relationship between leaf area and hydrothermal coefficient (r = +0.99) and a negative relationship between leaf area and ambient temperature (r = −0.97) were identified [10]. Rezanova [14], Patzukova [25], Tokhtar [18], and Panfilova [2] studied the anatomical structure of currant leaves and described the structure of the stomatal apparatus and the conduction system of *Ribes rubrum* L. and *Ribes American* L. According to anatomical studies, the red currant leaf had a mesomorphic structure characteristic of the *Ribesia* (Berl.) Jancz. subgenus. Spongy parenchyma prevailed over palisade parenchyma, epidermal cells were large enough, and on the upper side of the leaf, they were larger than on the lower one (**Figure 1**) [10]. It is shown that stomata are formed on the lower side of the leaf rarely and unevenly, at the level of the epidermis. There are varietal species differences in the size and number of stomata per 1 mm2 of leaf area, in the length of the closing cells, and in their shape. The size of stomata and the degree of their openness depend on the temperature and humidity of the air. During the drought, the degree of stomata opening decreases sharply.

The index of leaf mesostructure is labile in red currant genotypes of different ecological and genetic origins, including *Ribes petraeum* Wulf. ("Hollandische Rote"

**197**

*Physiological Features of Red Currant Adaptation to Drought and High Air Temperatures*

*Anatomical structure of a red currant leaf (cross sectional view, ×40), R. vulgare Lam. Bar represents 10 μm.*

and 1518-37-14), *Ribes vulgare* Lam. ("Jonkheer Van Tets," "Niva" and "Rosa"), and *Ribes multiflorum* Kit. ("Dana," 1426-21-80 and 1432-29-98), depending on the

*The average size (±S.E.) of the cells of adaxial epidermis of a leaf in red currant varieties and selected genotypes* 

High temperature and drought had different effects on cell size of adaxial epidermis and leaf mesostructure. In drought periods (2012, 2013) at the stages of active growth of shoots and formation of berries, the main cells of the adaxial epidermis in "Hollandische Rote" (*Ribes petraeum* Wulf) and 1426-21-80 (*Ribes multiflorum* Kit.) under the action of high temperatures (up to +31.2 … +28.6°C in May and +32.2 … +31.5°C in July) were somewhat stretched due to the decrease in turgor of the cells. The remaining samples showed cell compression in the tangent

Increased temperature and drought lead to the growth of parenchymal cells and increase of the overall thickness of the leaf (**Table 1**). The growth of mesophyll cells occurs mainly due to the increase in the volume of air-bearing cavities of the spongy parenchyma, which contributes to the improvement of gas exchange between the

In some previous studies [2, 26, 27], it was confirmed that significantly greater growth of spongy parenchyma cells and leaf blade thickness in dry periods were found in most samples of *Ribesia* (Berl.) Jancz. (with the exception of "Niva"). The largest increase in the thickness of the leaf was noted in "Hollandische Rote" and 1426-21-80. The authors consider these changes as a manifestation of high

genotypes and phase of plant development.

*of the Russian Research Institute of Fruit Crop Breeding, Orel [10].*

direction (parallel to the stem surface) (**Figure 2**).

leaf and the environment (**Figure 3**).

*DOI: http://dx.doi.org/10.5772/intechopen.85033*

**Figure 1.**

**Figure 2.**

*Physiological Features of Red Currant Adaptation to Drought and High Air Temperatures DOI: http://dx.doi.org/10.5772/intechopen.85033*

#### **Figure 1.**

*Drought - Detection and Solutions*

economic and biological characteristics [21].

**leaf due to drought and high temperature**

[6, 7]. The study of morphological features, structure of photosynthetic apparatus, and water exchange of plants in connection with the area of growth is the main condition for solving fundamental and applied problems in the biology of the culture. The use of physiological and biochemical rapid methods of diagnostics of plant resistance to adverse weather and climatic factors can significantly optimize the long breeding process, minimize crop losses, and obtain genotypes resistant to the destructive effects of climatic anomalies [8–10]. Plant organisms have different mechanisms of adaptation to stressors [9, 11]. Xeromorphic structure of a plant leaf, changes in a pigment complex, and water balance are important diagnostic signs of drought resistance and heat resistance [12–14]. Issues of adaptation of berry crops to drought and high temperatures are poorly studied. Red currant is one of the valuable berry crops due to the high content of vitamins, microelements, sugars, and organic acids. It is valued as a source of healthy nutrition [15–18]. Vitamin and the healing properties of the berries of this culture are also preserved in processed products [19]. Introduction is considered to be an important link in the distribution and production of new red currant genotypes. The success of the introduction is determined by the nature of the interaction of hereditary biological characteristics of plants with specific environmental conditions [18]. Red currants belong to the *Ribes* L. genus and *Ribesia* (Berl.) Jancz. subgenus. As a culture, it was developed on the basis of four species, i.e., *Ribes vulgare* Lam., *Ribes petraeum* Wulf., *Ribes multiflorum* Kit., and *Ribes rubrum* L., and their hybrids [20]. The world assortment of the *Ribes* L. genus includes more than 200 varieties; however, the genetic resources of the *Ribesia* (Berti.) Jancz. subgenus are poorly studied, since there are a number of wild species that exceed the existing varieties by a number of

**2. Anatomical, morphological, and physiological changes of a red currant** 

The study of the assimilation apparatus in red currants gives a complete picture of the plasticity of the genotype in relation to the ecological factors of the environment [11, 22–24]. The investigation of the anatomical and morphological features of red currant leaf structure showed that some morphological features, such as shape and venation, depend on the biological characteristics of the variety and the anatomical structure is more influenced by the growing conditions. During the periods with insufficient water supply, the leaf surface area decreased in all studied currant samples compared to optimal conditions. A positive relationship between leaf area and hydrothermal coefficient (r = +0.99) and a negative relationship between leaf area and ambient temperature (r = −0.97) were identified [10]. Rezanova [14], Patzukova [25], Tokhtar [18], and Panfilova [2] studied the anatomical structure of currant leaves and described the structure of the stomatal apparatus and the conduction system of *Ribes rubrum* L. and *Ribes American* L. According to anatomical studies, the red currant leaf had a mesomorphic structure characteristic of the *Ribesia* (Berl.) Jancz. subgenus. Spongy parenchyma prevailed over palisade parenchyma, epidermal cells were large enough, and on the upper side of the leaf, they were larger than on the lower one (**Figure 1**) [10]. It is shown that stomata are formed on the lower side of the leaf rarely and unevenly, at the level of the epidermis. There are varietal species differences in the size and number of stomata per

 of leaf area, in the length of the closing cells, and in their shape. The size of stomata and the degree of their openness depend on the temperature and humidity of the air. During the drought, the degree of stomata opening decreases sharply. The index of leaf mesostructure is labile in red currant genotypes of different ecological and genetic origins, including *Ribes petraeum* Wulf. ("Hollandische Rote"

**196**

1 mm2

#### **Figure 2.**

*The average size (±S.E.) of the cells of adaxial epidermis of a leaf in red currant varieties and selected genotypes of the Russian Research Institute of Fruit Crop Breeding, Orel [10].*

and 1518-37-14), *Ribes vulgare* Lam. ("Jonkheer Van Tets," "Niva" and "Rosa"), and *Ribes multiflorum* Kit. ("Dana," 1426-21-80 and 1432-29-98), depending on the genotypes and phase of plant development.

High temperature and drought had different effects on cell size of adaxial epidermis and leaf mesostructure. In drought periods (2012, 2013) at the stages of active growth of shoots and formation of berries, the main cells of the adaxial epidermis in "Hollandische Rote" (*Ribes petraeum* Wulf) and 1426-21-80 (*Ribes multiflorum* Kit.) under the action of high temperatures (up to +31.2 … +28.6°C in May and +32.2 … +31.5°C in July) were somewhat stretched due to the decrease in turgor of the cells. The remaining samples showed cell compression in the tangent direction (parallel to the stem surface) (**Figure 2**).

Increased temperature and drought lead to the growth of parenchymal cells and increase of the overall thickness of the leaf (**Table 1**). The growth of mesophyll cells occurs mainly due to the increase in the volume of air-bearing cavities of the spongy parenchyma, which contributes to the improvement of gas exchange between the leaf and the environment (**Figure 3**).

In some previous studies [2, 26, 27], it was confirmed that significantly greater growth of spongy parenchyma cells and leaf blade thickness in dry periods were found in most samples of *Ribesia* (Berl.) Jancz. (with the exception of "Niva"). The largest increase in the thickness of the leaf was noted in "Hollandische Rote" and 1426-21-80. The authors consider these changes as a manifestation of high


*Notes: PP—palisade parenchyma, μm; SP—sponge parenchyma, μm; TLT—total leaf thickness, μm. LSD05 for palisade parenchyma A = 1.57, B = 2.56, and AB = 4.42; LSD05 for sponge parenchyma A = 1.92, B = 3.14, and AB = 5.43; LSD05 for total leaf thickness A = 1.39, B = 2.27, and AB = 3.93.*

#### **Table 1.**

*Leaf mesostructural parameters in red currant varieties from the Russian Research Institute of Fruit Crop Breeding, Orel, in 2011–2013 vegetation period [10].*

#### **Figure 3.**

*The leaf mesophyll cells in a red currant exposed to drought ((cross sectional view, ×40), R. multiflorum Kit.). Bar represents 10 μm.*

adaptability of the anatomical structure of the leaf to stressors (high temperature) during the growing season (**Table 1**).

Knowledge of the anatomical structure of the leaves helps to fully reveal the biological characteristics of the variety and species as well as the flow of the most important physiological processes [28]. In the process of evolution, many currant species have acquired a high potential of photosynthetic productivity, and, for the most part, in the real environment, this potential is not fully used [29, 30].

Drought is one of the reasons for the decrease in the intensity of photosynthesis, respiration, and changes in the hormonal status of plants. Violation of hormonal metabolism significantly increases the process of natural fall of the ovaries of red currants, as well as the appearance of necrotic points on the leaves and a decrease in the number of laid generative buds; leads to a decrease in yield, during both current and subsequent years; and also reduces the stability of plants in winter [31–33].

**199**

**Figure 4.**

*Physiological Features of Red Currant Adaptation to Drought and High Air Temperatures*

The process of photosynthesis largely depends on the quantitative and qualitative composition of pigments. Changes in the pigment complex can be considered as important mechanisms of culture adaptation to environmental conditions. The impact of high temperatures and low soil moisture leads to a decrease in the concentration of chlorophyll [22, 34–36]. Studies of different red currant species have confirmed the impact of air and soil drought on the work of

In the dry period (in the Orel region it was 2012), there was a decrease in the content of chlorophyll *a* and chlorophylls *a*+*b* in the leaves of all red currant genotypes in comparison with the favorable weather conditions (2011) (**Figure 4**). A sharp (maximum) decrease in the number of pigments was observed in all derivatives of *R. vulgare* Lam. in 2012; the minimum decrease was observed in the representatives of *R. petraeum* Wulf. and *R. multiflorum* Kit. A slight decrease in

Drought at high temperatures stimulates the formation of carotenoids in the cell, which is consistent with the literature data on the protective function of this group of pigments under stress [5, 37, 38]. In the representatives of *Ribesia* (Berl.) Jancz. subgenus, the content of carotenoids in drought conditions increased by 2–3 times compared to a favorable period. A positive correlation in red currants was found between the carotenoid content and temperature (r = +0.77) [2, 10]. An indirect indicator of drought resistance and high temperature is the ratio of the sum of chlorophylls to carotenoids [23, 39, 40]. In stressful conditions, the high value of this indicator was observed in the variety "Hollandische Rote" (the value of the coefficient 5.14) and the selected form 1426-21-80 (the value of the coefficient 5.51), which may indicate the stability of these samples to drought and high summer temperatures. Hydrothermal regime affects productivity by affecting the functional state of plants, which was confirmed by high correlations between the amount of chlorophyll *a* and yield (r = +0.85) and the sum of chlorophylls and

*Content of chlorophyll a and sum of chlorophylls a+b in red currant varieties and selected genotypes of the* 

*Russian Research Institute of Fruit Crop Breeding, Orel [10].*

drought in 2013 contributed to a slight increase in pigment content.

*DOI: http://dx.doi.org/10.5772/intechopen.85033*

the assimilation apparatus.

yield (r = +0.78) [10].

#### *Physiological Features of Red Currant Adaptation to Drought and High Air Temperatures DOI: http://dx.doi.org/10.5772/intechopen.85033*

The process of photosynthesis largely depends on the quantitative and qualitative composition of pigments. Changes in the pigment complex can be considered as important mechanisms of culture adaptation to environmental conditions. The impact of high temperatures and low soil moisture leads to a decrease in the concentration of chlorophyll [22, 34–36]. Studies of different red currant species have confirmed the impact of air and soil drought on the work of the assimilation apparatus.

In the dry period (in the Orel region it was 2012), there was a decrease in the content of chlorophyll *a* and chlorophylls *a*+*b* in the leaves of all red currant genotypes in comparison with the favorable weather conditions (2011) (**Figure 4**).

A sharp (maximum) decrease in the number of pigments was observed in all derivatives of *R. vulgare* Lam. in 2012; the minimum decrease was observed in the representatives of *R. petraeum* Wulf. and *R. multiflorum* Kit. A slight decrease in drought in 2013 contributed to a slight increase in pigment content.

Drought at high temperatures stimulates the formation of carotenoids in the cell, which is consistent with the literature data on the protective function of this group of pigments under stress [5, 37, 38]. In the representatives of *Ribesia* (Berl.) Jancz. subgenus, the content of carotenoids in drought conditions increased by 2–3 times compared to a favorable period. A positive correlation in red currants was found between the carotenoid content and temperature (r = +0.77) [2, 10]. An indirect indicator of drought resistance and high temperature is the ratio of the sum of chlorophylls to carotenoids [23, 39, 40]. In stressful conditions, the high value of this indicator was observed in the variety "Hollandische Rote" (the value of the coefficient 5.14) and the selected form 1426-21-80 (the value of the coefficient 5.51), which may indicate the stability of these samples to drought and high summer temperatures. Hydrothermal regime affects productivity by affecting the functional state of plants, which was confirmed by high correlations between the amount of chlorophyll *a* and yield (r = +0.85) and the sum of chlorophylls and yield (r = +0.78) [10].

#### **Figure 4.**

*Drought - Detection and Solutions*

**Variety name/code (В) Year (А)**

*AB = 5.43; LSD05 for total leaf thickness A = 1.39, B = 2.27, and AB = 3.93.*

*Fruit Crop Breeding, Orel, in 2011–2013 vegetation period [10].*

*Leaf mesostructural parameters in red currant varieties from the Russian Research Institute of* 

**2011 2012 2013 PP SP TLT PP SP TLT PP SP TLT**

1426-21-80 10.29 13.62 26.94 12.00 20.00 37.30 9.75 15.80 29.91 "Hollandische Rote" 9.56 15.24 27.70 11.25 18.45 35.35 9.55 16.95 31.40 "Niva" 9.28 12.65 24.63 10.15 15.35 29.60 10.35 15.30 29.10 "Dana" 8.10 12.00 22.70 10.05 16.30 29.92 9.10 14.85 27.70 1432-29-98 7.90 12.35 23.25 11.65 17.55 33.65 10.15 15.10 29.10 1518-37-14 7.70 14.68 25.38 9.15 18.15 30.80 8.55 16.90 29.15 "Jonkheer Van Tets" 7.30 10.10 20.33 10.50 15.90 30.05 9.00 12.30 24.80 "Rosa" 6.80 11.23 20.53 7.95 13.85 25.60 8.10 13.80 25.10 *Notes: PP—palisade parenchyma, μm; SP—sponge parenchyma, μm; TLT—total leaf thickness, μm. LSD05 for palisade parenchyma A = 1.57, B = 2.56, and AB = 4.42; LSD05 for sponge parenchyma A = 1.92, B = 3.14, and* 

**198**

**Figure 3.**

**Table 1.**

*represents 10 μm.*

adaptability of the anatomical structure of the leaf to stressors (high temperature)

*The leaf mesophyll cells in a red currant exposed to drought ((cross sectional view, ×40), R. multiflorum Kit.). Bar* 

Knowledge of the anatomical structure of the leaves helps to fully reveal the biological characteristics of the variety and species as well as the flow of the most important physiological processes [28]. In the process of evolution, many currant species have acquired a high potential of photosynthetic productivity, and, for the

Drought is one of the reasons for the decrease in the intensity of photosynthesis, respiration, and changes in the hormonal status of plants. Violation of hormonal metabolism significantly increases the process of natural fall of the ovaries of red currants, as well as the appearance of necrotic points on the leaves and a decrease in the number of laid generative buds; leads to a decrease in yield, during both current and subsequent years; and also reduces the stability of plants in winter [31–33].

most part, in the real environment, this potential is not fully used [29, 30].

during the growing season (**Table 1**).

*Content of chlorophyll a and sum of chlorophylls a+b in red currant varieties and selected genotypes of the Russian Research Institute of Fruit Crop Breeding, Orel [10].*
