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Full Research Article

Physiological and Biochemical Characterization of Pea Genotypes for High Temperature Stress Tolerance

V
Vikash Chaudhary1
M
Madhurya Ray1
K
Kalyan Barman2
M
Manju Jat1
I
Isharani Biswal1
M
Md. Afjal Ahmad1,*
1Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005, Uttar Pradesh, India.
2Department of Horticulture, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005, Uttar Pradesh, India.

ABSTRACT

Background: An experiment was conducted during Rabi 2023-2024 at Banaras Hindu University, Varanasi, to assess the impact of high-temperature stress on four pea (Pisum sativum L.) genotypes: Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3) and Kashi Shakti (V4).

Methods: Plants were evaluated under both optimal and elevated temperature conditions for morphological, physiological, biochemical and yield attributes.

Result: High-temperature stress significantly reduced germination percentage, shoot and root length, relative water content, membrane thermo-stability index and chlorophyll stability index. Among genotypes, V3 exhibited the highest germination (85%) under optimal conditions, whereas V2 showed the greatest decline (45%) under stress. Biochemical parameters, including chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, protein and soluble sugars, decreased markedly under heat stress, with V3 maintaining relatively higher levels, while V2 remained the most susceptible. In contrast, stress indicators such as proline accumulation and catalase activity increased, particularly in V4, suggesting enhanced antioxidative defense. Yield traits, including pods per plant and seeds per pod, were also adversely affected under high temperature, although V3 and V4 performed best under both optimal conditions and heat stress condition. Overall, Kashi Samridhi (V3) and Kashi Shakti (V4) demonstrated superior heat tolerance, highlighting their potential utility in breeding programs aimed at developing climate-resilient pea genotypes.

INTRODUCTION

The Fabaceae family includes the diploid (2n=14) self-pollinating pea (Pisum sativum var. L) (rabi season crop), which is originated in Ethiopia, the Mediterranean and Central Asia. The crop is grown all over the world for its edible seeds and pods, which are eaten fresh, dried, canned and frozen. Peas are a good source of fiber, protein, vitamins and minerals (Devi et al., 2023). Peas have 23-31% protein along with significant levels of lysine, 4-7% fiber and 35-40% starch, which makes them a useful addition to diets based on cereals. Extended exposure to elevated temperatures can impair cellular processes by denaturing proteins, rupturing membranes, impeding photosynthesis and diminishing root and shoot growth (Hasanuzzaman et al., 2013; Ibrahim et al., 2019). Reduced shoot dry mass, reduced net assimilation and changed root architecture are important physiological and biochemical impacts. Indirect effect includes deactivation of enzymes, inhibition of protein synthesis and decreased photosynthetic efficiency are indirect impacts, diminished protein function and loss of membrane stability are direct effects (Jiang et al., 2020). Since a cool season crop, during its maturity stage the crop is exposed to high temperatures, which can result in stunted growth, poor pod formation and decreased yields (Huggins et al., 2018). Therefore, identifying heat-tolerant pea genotypes requires analyzing germplasm for characteristics associated with thermotolerance. Avoidance strategies like leaf rolling and transpirational cooling, as well as tolerance strategies like osmo-protectant accumulation, heat shock protein synthesis and membrane stability, are how plants combat heat stress. High temperatures can trigger early blooming in some crops, which lowers yield (Mohapatra et al., 2020; Jat et al., 2024). In order to ensure sustainable pea production under rising temperatures, the current study was carried out to investigate how specific morphological and physiological traits in various pea genotypes are affected by high temperatures. We have also evaluated the effects of heat stress on yield components and biological features using physiological and biochemical reactions and it identified and screened genotypes for high heat tolerance.

MATERIALS AND METHODS

Experimental conditions
 
The study was carried out in the Rabi season of 2023-2024 to assess the impact of high temperature on morpho-physiological and biochemical and yield of four genotypes of pea (Kashi Mukti, Kashi Nandini, Kashi Samridhi, Kashi Shakti). Located at 25°182 N latitude, 83°032 E longitude and 75.7 m above mean sea level, the experiment was conducted in pots kept in the greenhouse of the Horticulture Unit and the laboratory of the Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The genotypes were obtained from ICAR-IIVR-Varanasi. which were pure and disease free. The genotypes were chosen because they are dwarf, early maturing and high yielding varieties. The high temperature treatment was imposed 50 days after emergence (50 DAE), in plant growth chambers (3 m × 3 m) at 35°C temperature under a 14/10-hour day/night cycle and 85% relative humidity. Pots were filled with a sand: vermiculite: FYM mixture (2:1:1) after being carefully cleaned and dried. On December 11, 2023, five seeds were planted in each pot (Fig 1). Plants were regularly irrigated and maintained under greenhouse conditions until imposition of heat stress in plant growth chamber (Table 1 and Table 2). 3 pots per genotype per treatment per replicate was used for the experiment. Each pot was considered an experimental unit and there were 5 plants retained in each pot after thinning.

Fig 1: General layout of the pot experiment.



Table 1: Meteorological data of Rabi season 2023-24.



Table 2: Details of the experiment.


 
Determination of morpho-physiological parameters
 
The pots were arranged in completely randomized design in green house. The high temperature treatment was imposed 50 days after emergence (50 DAE), in plant growth chambers (3 m × 3 m) at 35°C temperature under a 14/10 hours day/night cycle and 85% relative humidity. The following morpho-physiological, biochemical and yield parameters were observed at after heat stress initiation. Using petri plate assays, the percentage of seeds that germinated relative to the total number of seeds sown was measured in a laboratory setting. Shoot length (cm) was measured from the base of the shoot to the growing tip using a thread and meter scale. Root length (cm) was similarly measured, averaged from three plants per replicate per treatment. Root length was obtained by taking average of root length of three plants obtained from the three replications under each treatment. Root length is expressed in centimetres.
       
Chlorophyll Stability Index was assessed by keeping one set of 0.1 g leaf sample in a test tube containing 10 ml distilled water at 55°C and another set of 0.1 g leaf sample in a test tube containing 10 ml distilled water at room temperature and calculated as:


Membrane stability index (MSI) was determined by placing 0.1 g leaf samples in test tubes with 10 mL distilled water. One set was heated at 40°C for 30 min (C1) and another set was boiled at 100°C for 10 min (C2). Conductivity was measured after cooling.
 
MSI (%) = [1 - (C1/C2)] × 100
 
Relative water content was determined from fresh, turgid and dry weights using


Determination of biochemical parameters
 
Chlorophyll a, chlorophyll b and total chlorophyll contents were quantified from DMSO extracts using absorbance at 645 and 663 nm, calculated as:
 
Chl a (mg g-1 FW) = (12.7A663 - 2.69A645) × V/(1000W); Chl b (mg g-1 FW) = (22.9A645 4.68A663) × V/(1000 W)
 
Total Chl (mg g-1 FW) = (20.2A645+ 8.02A663) × V/(1000 W)
 
where
V = Extract volume.
W= Sample weight.
       
Carotenoid content was estimated from at 450 nm using the formula:
 
Carotenoids (mg g-1 FW) = 4.49 × A450 -0.26 (2.02 × A645+8.02 × A663) × (V/1000 × W)
 
Total protein content was determined from leaf tissues homogenized in 0.2 M Tris-HCl and quantified by the Bradford assay using absorbance at 595 nm and a BSA standard curve. Total soluble sugars were extracted in 80% ethanol and reducing sugars were determined using Somogyi–Nelson reagents with absorbance at 530 nm, calculated from a glucose standard curve (Srivastava et al., 2012).
       
Catalase activity was assayed spectrophotometrically in leaf samples at 60 DAE. Catalase activity was assayed as per protocol of (Aebi et al., 1984).
       
Proline estimation was based on the formation of brick red coloured proline- ninhydrin complex in acidic medium. This complex was soluble in toluene and it was separated from aqueous phase. This ensured that there was no interference with other amino acids, which also farmed a blue coloured complex with ninhydrin. The toluene solubilised brick red coloured complex absorbed at 520 nm. Free proline content in leaves was determined following the method of Bates et al. (1973). The protocol was based on the formation of red coloured formazine substance by proline with ninhydrin in acidic medium, which was soluble in organic solvents like toluene.
       
The statistical analysis including ANOVA and post hoc analysis DMRT (Duncan’s Multiple Range Test) was done using OPSTAT (https://opstat.somee.com/opstat/).

RESULTS AND DISCUSSION

Morpho-physiological parameters
 
The results showed that high temperature had negative effect on the germination percentage of garden pea. The germination percentage descreased significantly under high temperature. Shoot length was greatest under optimum temperature in Kashi Samridhi (V3) with a mean value 58.13 cm. In high temperature condition shoot length was decreased due to heat stress, plants often undergo a reduction in the net assimilation rate, which is closely associated with plant growth. Under high temperature root lengths were significantly reduced in all varieties. At 60 days after emergence (DAE), the highest mean root length was observed in the variety Kashi Samridhi (V3) when grown at the optimum temperature and the mean value of root length for this variety was 12.83 cm. At 60 days after emergence (DAE), the highest mean relative water content was observed in Kashi Samridhi (V3), with a mean value of 89.66%, among the four different genotypes of pea grown under optimum temperature (T1). A significant reduction in relative water content was observed when the genotypes were subjected to high temperature stress, under these conditions, the variety Kashi Mukti (V1) exhibited the lowest mean relative water content with a mean value of 62.33%. Membrane thermo-stability index reduction has been noticed in high temperature condition due to enhanced membrane leakage (Islam et al., 2025). Kashi Nandini (V2) has least membrane stability index. The reduction in membrane thermo-stability index (MSI) at elevated temperatures is mainly due to alterations in lipid composition, oxidative stress from increased reactive oxygen species (ROS) and protein denaturation (Dasgan et al., 2021; Sharma et al., 2023). In high temperature condition chlorophyll stability index has also been found to significantly decrease. Highest Chlorophyll stability index was observed in the variety Kashi Shakti (V4) under favourable temperature and least chlorophyll stability index was observed in Kashi Mukti (V1). Elevated temperature speeds up the degradation of chlorophyll, a process where enzymes known as chlorophyllases become activated and reactive oxygen species (ROS) accumulate (Lamichaney et al., 2021; Mukherjee et al., 2025) (Table 3).

Table 3: The variation of morpho-physiological parameters across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2- High Temperature).


 
Biochemical parameters
 
At 60 DAE, chlorophyll a, b and total chlorophyll were recorded. Significantly greater value for chlorophyll ‘a’, ‘b’, total chlorophyll content was obtained in the Kashi Samridhi (V3), with a mean value of 1.501 mg/g FW, 0.524 mg/g FW, 2.027 mg/g FW under optimum temperature (T1) in comparison to the other genotypes. Chlorophyll ‘a’, ‘b’ and total chlorophyll content was significantly decreased when pea plants are exposed to high temperature condition (Fig 2). The reduction in carotenoid content under high temperature was not significant. Kashi Samridhi (V3) showed the highest carotenoid content and Kashi Mukti (V1) the lowest under high temperature. Leaf protein content decreased with increasing temperature due to denaturation (Devi et al., 2025). The genotype Kashi Shakti (V4) recorded highest mean value of protein content whereas under high temperature Kashi Mukti (V1) recorded lowest. High temperatures can cause proteins to denature, leading to the unfolding of their structures (Rampe et al., 2026). According to the experimental findings it can be concluded that the total soluble sugar content got reduced significantly under heat stress. Kashi Samridhi (V3) had the highest soluble sugar content and  Kashi Nandini (V2) the least under high temperature regime (Fig 3). High temperature can significantly impact the soluble sugar content in peas. Plants under high-temperature conditions tend to have increased respiration rates, which leads to higher sugar consumption and consequently less sugar accumulation in plant tissues (Biswal et al., 2025; Reddy et al., 2025). Proline content and catalase activity was significantly increased when pea plants are exposed to high temperature condition. Highest amount of proline and catalase activity was found in the genotype Kashi Shakti (V4). The increased ROS detoxification and enhancement of antioxidant enzymes are responsible for the better performance of V3 and V4 genotypes. All varieties showed a significant reduction in pods per plant and seeds per pod under high temperature as photosynthates gets allocated more towards injury repairing caused due to heat stress (Hitesh et al., 2026; Sharma and Manjeet, 2020). Research indicates that elevated temperature heightens the chances of flower abortion and diminishes the pod-set ratio (Camejo et al., 2005; Ray et al., 2025) (Fig 4).

Fig 2: Variation of chlorophyll content (mg/g FW) across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2-High temperature).



Fig 3: Variation of different biochemical parameters across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2-High temperature).



Fig 4: Variation of different biochemical parameters across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2- High temperature).

CONCLUSION

High temperature stress significantly decreased growth and physiological performance in all pea genotypes, according to the study; however, Kashi Samridhi (V3) and Kashi Shakti (V4) as relatively heat-tolerant genotypes. Kashi Samridhi (V3) excelled in germination, growth parameters, water retention and biochemical traits under stress conditions. Meanwhile, Kashi Shakti demonstrated superior physiological adaptations, including chlorophyll stability, protein synthesis and enzyme activities. Therefore, Kashi Samridhi(V3) and Kashi Shakti (V4) are promising candidates for cultivation in heat-affected areas and for inclusion in heat tolerance breeding programs.

CONFLICT OF INTEREST

I hereby declare that on behalf of all the authors, there is no conflict of interest regarding the manuscript.

REFERENCES


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    Full Research Article

    Physiological and Biochemical Characterization of Pea Genotypes for High Temperature Stress Tolerance

    V
    Vikash Chaudhary1
    M
    Madhurya Ray1
    K
    Kalyan Barman2
    M
    Manju Jat1
    I
    Isharani Biswal1
    M
    Md. Afjal Ahmad1,*
    1Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005, Uttar Pradesh, India.
    2Department of Horticulture, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005, Uttar Pradesh, India.

    ABSTRACT

    Background: An experiment was conducted during Rabi 2023-2024 at Banaras Hindu University, Varanasi, to assess the impact of high-temperature stress on four pea (Pisum sativum L.) genotypes: Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3) and Kashi Shakti (V4).

    Methods: Plants were evaluated under both optimal and elevated temperature conditions for morphological, physiological, biochemical and yield attributes.

    Result: High-temperature stress significantly reduced germination percentage, shoot and root length, relative water content, membrane thermo-stability index and chlorophyll stability index. Among genotypes, V3 exhibited the highest germination (85%) under optimal conditions, whereas V2 showed the greatest decline (45%) under stress. Biochemical parameters, including chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, protein and soluble sugars, decreased markedly under heat stress, with V3 maintaining relatively higher levels, while V2 remained the most susceptible. In contrast, stress indicators such as proline accumulation and catalase activity increased, particularly in V4, suggesting enhanced antioxidative defense. Yield traits, including pods per plant and seeds per pod, were also adversely affected under high temperature, although V3 and V4 performed best under both optimal conditions and heat stress condition. Overall, Kashi Samridhi (V3) and Kashi Shakti (V4) demonstrated superior heat tolerance, highlighting their potential utility in breeding programs aimed at developing climate-resilient pea genotypes.

    INTRODUCTION

    The Fabaceae family includes the diploid (2n=14) self-pollinating pea (Pisum sativum var. L) (rabi season crop), which is originated in Ethiopia, the Mediterranean and Central Asia. The crop is grown all over the world for its edible seeds and pods, which are eaten fresh, dried, canned and frozen. Peas are a good source of fiber, protein, vitamins and minerals (Devi et al., 2023). Peas have 23-31% protein along with significant levels of lysine, 4-7% fiber and 35-40% starch, which makes them a useful addition to diets based on cereals. Extended exposure to elevated temperatures can impair cellular processes by denaturing proteins, rupturing membranes, impeding photosynthesis and diminishing root and shoot growth (Hasanuzzaman et al., 2013; Ibrahim et al., 2019). Reduced shoot dry mass, reduced net assimilation and changed root architecture are important physiological and biochemical impacts. Indirect effect includes deactivation of enzymes, inhibition of protein synthesis and decreased photosynthetic efficiency are indirect impacts, diminished protein function and loss of membrane stability are direct effects (Jiang et al., 2020). Since a cool season crop, during its maturity stage the crop is exposed to high temperatures, which can result in stunted growth, poor pod formation and decreased yields (Huggins et al., 2018). Therefore, identifying heat-tolerant pea genotypes requires analyzing germplasm for characteristics associated with thermotolerance. Avoidance strategies like leaf rolling and transpirational cooling, as well as tolerance strategies like osmo-protectant accumulation, heat shock protein synthesis and membrane stability, are how plants combat heat stress. High temperatures can trigger early blooming in some crops, which lowers yield (Mohapatra et al., 2020; Jat et al., 2024). In order to ensure sustainable pea production under rising temperatures, the current study was carried out to investigate how specific morphological and physiological traits in various pea genotypes are affected by high temperatures. We have also evaluated the effects of heat stress on yield components and biological features using physiological and biochemical reactions and it identified and screened genotypes for high heat tolerance.

    MATERIALS AND METHODS

    Experimental conditions
     
    The study was carried out in the Rabi season of 2023-2024 to assess the impact of high temperature on morpho-physiological and biochemical and yield of four genotypes of pea (Kashi Mukti, Kashi Nandini, Kashi Samridhi, Kashi Shakti). Located at 25°182 N latitude, 83°032 E longitude and 75.7 m above mean sea level, the experiment was conducted in pots kept in the greenhouse of the Horticulture Unit and the laboratory of the Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The genotypes were obtained from ICAR-IIVR-Varanasi. which were pure and disease free. The genotypes were chosen because they are dwarf, early maturing and high yielding varieties. The high temperature treatment was imposed 50 days after emergence (50 DAE), in plant growth chambers (3 m × 3 m) at 35°C temperature under a 14/10-hour day/night cycle and 85% relative humidity. Pots were filled with a sand: vermiculite: FYM mixture (2:1:1) after being carefully cleaned and dried. On December 11, 2023, five seeds were planted in each pot (Fig 1). Plants were regularly irrigated and maintained under greenhouse conditions until imposition of heat stress in plant growth chamber (Table 1 and Table 2). 3 pots per genotype per treatment per replicate was used for the experiment. Each pot was considered an experimental unit and there were 5 plants retained in each pot after thinning.

    Fig 1: General layout of the pot experiment.



    Table 1: Meteorological data of Rabi season 2023-24.



    Table 2: Details of the experiment.


     
    Determination of morpho-physiological parameters
     
    The pots were arranged in completely randomized design in green house. The high temperature treatment was imposed 50 days after emergence (50 DAE), in plant growth chambers (3 m × 3 m) at 35°C temperature under a 14/10 hours day/night cycle and 85% relative humidity. The following morpho-physiological, biochemical and yield parameters were observed at after heat stress initiation. Using petri plate assays, the percentage of seeds that germinated relative to the total number of seeds sown was measured in a laboratory setting. Shoot length (cm) was measured from the base of the shoot to the growing tip using a thread and meter scale. Root length (cm) was similarly measured, averaged from three plants per replicate per treatment. Root length was obtained by taking average of root length of three plants obtained from the three replications under each treatment. Root length is expressed in centimetres.
           
    Chlorophyll Stability Index was assessed by keeping one set of 0.1 g leaf sample in a test tube containing 10 ml distilled water at 55°C and another set of 0.1 g leaf sample in a test tube containing 10 ml distilled water at room temperature and calculated as:


    Membrane stability index (MSI) was determined by placing 0.1 g leaf samples in test tubes with 10 mL distilled water. One set was heated at 40°C for 30 min (C1) and another set was boiled at 100°C for 10 min (C2). Conductivity was measured after cooling.
     
    MSI (%) = [1 - (C1/C2)] × 100
     
    Relative water content was determined from fresh, turgid and dry weights using


    Determination of biochemical parameters
     
    Chlorophyll a, chlorophyll b and total chlorophyll contents were quantified from DMSO extracts using absorbance at 645 and 663 nm, calculated as:
     
    Chl a (mg g-1 FW) = (12.7A663 - 2.69A645) × V/(1000W); Chl b (mg g-1 FW) = (22.9A645 4.68A663) × V/(1000 W)
     
    Total Chl (mg g-1 FW) = (20.2A645+ 8.02A663) × V/(1000 W)
     
    where
    V = Extract volume.
    W= Sample weight.
           
    Carotenoid content was estimated from at 450 nm using the formula:
     
    Carotenoids (mg g-1 FW) = 4.49 × A450 -0.26 (2.02 × A645+8.02 × A663) × (V/1000 × W)
     
    Total protein content was determined from leaf tissues homogenized in 0.2 M Tris-HCl and quantified by the Bradford assay using absorbance at 595 nm and a BSA standard curve. Total soluble sugars were extracted in 80% ethanol and reducing sugars were determined using Somogyi–Nelson reagents with absorbance at 530 nm, calculated from a glucose standard curve (Srivastava et al., 2012).
           
    Catalase activity was assayed spectrophotometrically in leaf samples at 60 DAE. Catalase activity was assayed as per protocol of (Aebi et al., 1984).
           
    Proline estimation was based on the formation of brick red coloured proline- ninhydrin complex in acidic medium. This complex was soluble in toluene and it was separated from aqueous phase. This ensured that there was no interference with other amino acids, which also farmed a blue coloured complex with ninhydrin. The toluene solubilised brick red coloured complex absorbed at 520 nm. Free proline content in leaves was determined following the method of Bates et al. (1973). The protocol was based on the formation of red coloured formazine substance by proline with ninhydrin in acidic medium, which was soluble in organic solvents like toluene.
           
    The statistical analysis including ANOVA and post hoc analysis DMRT (Duncan’s Multiple Range Test) was done using OPSTAT (https://opstat.somee.com/opstat/).

    RESULTS AND DISCUSSION

    Morpho-physiological parameters
     
    The results showed that high temperature had negative effect on the germination percentage of garden pea. The germination percentage descreased significantly under high temperature. Shoot length was greatest under optimum temperature in Kashi Samridhi (V3) with a mean value 58.13 cm. In high temperature condition shoot length was decreased due to heat stress, plants often undergo a reduction in the net assimilation rate, which is closely associated with plant growth. Under high temperature root lengths were significantly reduced in all varieties. At 60 days after emergence (DAE), the highest mean root length was observed in the variety Kashi Samridhi (V3) when grown at the optimum temperature and the mean value of root length for this variety was 12.83 cm. At 60 days after emergence (DAE), the highest mean relative water content was observed in Kashi Samridhi (V3), with a mean value of 89.66%, among the four different genotypes of pea grown under optimum temperature (T1). A significant reduction in relative water content was observed when the genotypes were subjected to high temperature stress, under these conditions, the variety Kashi Mukti (V1) exhibited the lowest mean relative water content with a mean value of 62.33%. Membrane thermo-stability index reduction has been noticed in high temperature condition due to enhanced membrane leakage (Islam et al., 2025). Kashi Nandini (V2) has least membrane stability index. The reduction in membrane thermo-stability index (MSI) at elevated temperatures is mainly due to alterations in lipid composition, oxidative stress from increased reactive oxygen species (ROS) and protein denaturation (Dasgan et al., 2021; Sharma et al., 2023). In high temperature condition chlorophyll stability index has also been found to significantly decrease. Highest Chlorophyll stability index was observed in the variety Kashi Shakti (V4) under favourable temperature and least chlorophyll stability index was observed in Kashi Mukti (V1). Elevated temperature speeds up the degradation of chlorophyll, a process where enzymes known as chlorophyllases become activated and reactive oxygen species (ROS) accumulate (Lamichaney et al., 2021; Mukherjee et al., 2025) (Table 3).

    Table 3: The variation of morpho-physiological parameters across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2- High Temperature).


     
    Biochemical parameters
     
    At 60 DAE, chlorophyll a, b and total chlorophyll were recorded. Significantly greater value for chlorophyll ‘a’, ‘b’, total chlorophyll content was obtained in the Kashi Samridhi (V3), with a mean value of 1.501 mg/g FW, 0.524 mg/g FW, 2.027 mg/g FW under optimum temperature (T1) in comparison to the other genotypes. Chlorophyll ‘a’, ‘b’ and total chlorophyll content was significantly decreased when pea plants are exposed to high temperature condition (Fig 2). The reduction in carotenoid content under high temperature was not significant. Kashi Samridhi (V3) showed the highest carotenoid content and Kashi Mukti (V1) the lowest under high temperature. Leaf protein content decreased with increasing temperature due to denaturation (Devi et al., 2025). The genotype Kashi Shakti (V4) recorded highest mean value of protein content whereas under high temperature Kashi Mukti (V1) recorded lowest. High temperatures can cause proteins to denature, leading to the unfolding of their structures (Rampe et al., 2026). According to the experimental findings it can be concluded that the total soluble sugar content got reduced significantly under heat stress. Kashi Samridhi (V3) had the highest soluble sugar content and  Kashi Nandini (V2) the least under high temperature regime (Fig 3). High temperature can significantly impact the soluble sugar content in peas. Plants under high-temperature conditions tend to have increased respiration rates, which leads to higher sugar consumption and consequently less sugar accumulation in plant tissues (Biswal et al., 2025; Reddy et al., 2025). Proline content and catalase activity was significantly increased when pea plants are exposed to high temperature condition. Highest amount of proline and catalase activity was found in the genotype Kashi Shakti (V4). The increased ROS detoxification and enhancement of antioxidant enzymes are responsible for the better performance of V3 and V4 genotypes. All varieties showed a significant reduction in pods per plant and seeds per pod under high temperature as photosynthates gets allocated more towards injury repairing caused due to heat stress (Hitesh et al., 2026; Sharma and Manjeet, 2020). Research indicates that elevated temperature heightens the chances of flower abortion and diminishes the pod-set ratio (Camejo et al., 2005; Ray et al., 2025) (Fig 4).

    Fig 2: Variation of chlorophyll content (mg/g FW) across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2-High temperature).



    Fig 3: Variation of different biochemical parameters across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2-High temperature).



    Fig 4: Variation of different biochemical parameters across varieties [Kashi Mukti (V1), Kashi Nandini (V2), Kashi Samridhi (V3), Kashi Shakti (V4)] and temperature regimes (T1-Control, T2- High temperature).

    CONCLUSION

    High temperature stress significantly decreased growth and physiological performance in all pea genotypes, according to the study; however, Kashi Samridhi (V3) and Kashi Shakti (V4) as relatively heat-tolerant genotypes. Kashi Samridhi (V3) excelled in germination, growth parameters, water retention and biochemical traits under stress conditions. Meanwhile, Kashi Shakti demonstrated superior physiological adaptations, including chlorophyll stability, protein synthesis and enzyme activities. Therefore, Kashi Samridhi(V3) and Kashi Shakti (V4) are promising candidates for cultivation in heat-affected areas and for inclusion in heat tolerance breeding programs.

    CONFLICT OF INTEREST

    I hereby declare that on behalf of all the authors, there is no conflict of interest regarding the manuscript.

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