Studies on Leaf Characteristics of Chickpea (Cicer arietinum L.) and Their Contribution to Seed Yield under Different Temperature Stress in North West India

In arid and semi-arid regions of India the increasing temperature causes climate change that lead to adverse effects on agricultural crops (Wahid and Close, 2007). Chickpea (Cicer arietinum L.) is cool season crops and it is normally sown during second fortnight of October and November in Northern India. Due to the fluctuations in the pattern of monsoon and late harvest of preceding kharifcrop like rice and sugarcane its sowing is delayed which ultimately results in poor seed yield (Wang et al., 2006). Any variation in temperature causes significant changes in legume crops because they are very sensitive to variation in temperature as the late-sown crop is exposed to high temperatures (>35°C) at its reproductive stage in the months of March- April and early sown crops experienced low temperature (<5°C) in the month of December-January (Kumar et al., 2012). The adoption of good management practices like sowing dates and tolerant genotypes can enhance the seed yield of chickpea under current scenario of climate change. Sowing time of any crop depends upon specific varieties and particular area so optimum sowing time and highly productive cultivars can boost growth, development and yield of particular crops because sowing time can influence many climatic factors like temperature, moisture, rainfall and sunshine hours (Bazvand et al., 2015). Optimum sowing time coordinates all environmental factors throughout the life cycle of plants from germination to the harvesting. Among all environmental factors the temperature stress is main concerns in agriculture from last decades. High temperature stress can affect important physiological processes of plant cell like photosynthesis, membrane stability, source sink relationship, water status and production of reactive oxygen species (Wahid and Close, 2007) leading to poor seed yield. In other hand low Temperature (<10°C)also causes adverse effects on physiological processes ranging from plant water status, photosynthesis to reactive oxygen species (ROS) resulted into losses in chickpea yield from 15-20% (Chaturvedi et al., 2009). In response to temperature stress the plant leaves plays important role by production of photosynthates, metabolites, antioxidants, phytohormones and accumulation of pigments like carotenoids and anthocyanin for repair, defense and physiological recovery of plant cells (Bita and Gerats, 2013). Therefore, it is very important to study leaves traits to overcome the impact of high or low temperature on chickpea productivity with identification of new chickpea varieties having higher tolerance to temperature stress are needed.

The field trials was conducted at Pulses Section, Chaudhary Charan Singh Haryana Agricultural University, Hisar for two consecutive years (2017-2019) with three sowing dates (15^th October, 15^th November and 15^th December) and ten chickpea genotypes namely HC-1, HC-3, HC-5 (Released varieties), H12-64, H13-01, H13-02, H14-01 and H14-04 (From AVT- advanced varietal trials) ICCV 88503 (Check), ICCV 92944 (Check) were taken in a randomized block design (RBD) with three replications to study the leaf characteristics of chickpea under different temperature stress. Five plants were randomly selected in each plot and sampling was done at 50% flowering stage. The actual mean weekly meteorological data of both years (2017-18 and 2018-19), recorded at observatory located at field of Agro meteorological department, Chaudhary Charan Singh Haryana Agricultural University, Hisar are depicted in Fig 1 and 2. Analysis of soil parameters was done by adopting standard analytical methods. The nutrient and moisture status were controlled by the application of recommended dose of fertilisers and irrigation according to package and practices given by Chaudhary Charan Singh Haryana Agricultural University.
 
 

 

 
Specific leaf area (SLA)
 
Specific leaf area calculated by formula of Kvet et al., (1971).
   
Leaf area index (LAI)
 
Leaf Area Index (LAI)calculated by formula of Williams (1946).
   
Net assimilation rate (NAR) (g g^-1day^-1)
 
NAR was calculated by formula given by Williams (1946).
   
Where,
W₁ and W₂= Dry weight of whole plant at time.
t₁ and t₂= Respectively.
L₁ and L₂= Leaf weights or leaf area at t₁ and t₂ respectivey.
t₁-t₂= Time interval in days. Here NAR was calculated between 60 and 90 DAS.
       
Chlorophyll a and Carotenoids content (mg/gm DW) were calculated by the method of Hiscox and Israelstam (1979).
       
Anthocyanin content (mg/gm DW) was estimated according to the method of Lobos et al., (2014).
       
Photochemical efficiency/quantum yield of PS-II (Fv/Fm) was measured as the chlorophyll fluorescence using a chlorofluorometer.
 
Statistical analysis
 
Data were analysed through (ANOVA) using Online Statistical Analysis Package (OPSTAT) software of Computer Section, CCS Haryana Agricultural University, Hisar by pooled analysis of both year (2017-18 and 2018-19).

In the present investigation the maximum specific leaf area (SLA) was observed in genotype H13-01 and H12-64 whereas minimum in H14-04 at 50% flowering stages (80-90 DAS). This might be due to genetic potential of genotypes. Among sowing dates, maximum specific leaf area (SLA) were observed in 15^th December and minimum were observed in 15^th November sowing (Table 1). This might be due to higher accumulation of dry matter in proportionate with leaf area in 15^th November sowing as compared to15^th October and 15^th December sowing due to suitable environmental condition prevailing at 15^th November sown crop. Similar results due to different sowing dates has also has been reported earlier in the literature by Mrudula et al., (2013); Patil et al., (2017) in chiPckpea.
 

       
The results of the present investigation showed that delayed sowing significantly decreased the leaf area index (Table 1). In present investigation, the minimum leaf area index (LAI) was observed in plants sown on 15^th December and maximum leaf area index was observed on 15^th November sowing followed by 15^th October sowing. This variation in leaf area index might be due to optimum temperature (maximum temp. 21.9°C, minimum temp. 7.2°C) prevailing at 15^th November sown crop that resulted into increased leaf area while low temperature (maximum temp. 17.1°C, minimum temp. 4.8°C)  at 15^th October sowing and high temperature (maximum temp. 38°C, minimum temp. 18.2°C)  in 15^th December sowing at 50% flowering stages (80-90 DAS) resulted into decreased leaf area index. The maximum leaf area index was observed in genotype H12-64 and H13-01 whereas minimum leaf area index was observed in genotype H14-04. This variation in genotypes might be due their tolerance behavior against temperature stress. Similar results also observed due to different sowing dates (Mrudula et al., 2013; Patil et al., 2017) in chickpea.
       
The minimum net assimilation rate (NAR) was observed in plants sown on 15^th December and maximum was on 15^th November sown crop. This might be due to suitable environmental conditions that resulted into more accumulation of dry matter in 15^th November sowing at 50% flowering stages (80-90 DAS) as compared to other sowing dates. The maximum net assimilation rate was observed in genotype H12-64 and H13-01 whereas, minimum was in H14-04. The variation in genotypes might be due their high leaf area index and tolerance behavior against temperature stress.Similar results due to sowing dates has also reported earlier in the literature (Mrudula et al., 2013; Patil et al., 2017) in chickpea.
       
In present investigation, minimum chlorophyll (CHL) and carotenoids (CHR) contents were observed in plants sown on 15^th December and maximum were observed on 15^th November sowing followed by 15^th October sowing. This variation in chlorophyll and carotenoids contents due to optimum temperature (maximum temp. 21.9°C, minimum temp. 7.2°C) prevailing at 15^th November sown crop and high leaf area index while low temperature (maximum temp. 17.1°C, minimum temp. 4.8°C) at 15thOctober and high temperature (maximum temp. 38°C, minimum temp. 18.2°C) in 15^th December sowing at 50% flowering stages (80-90 DAS) resulted into decreased chlorophyll and carotenoids contents (Table 1). These results also in the same line as observed by Kumar et al., (2011) in mungbean; Kaushal et al., 2011 in chickpea). Among genotypes, highest chlorophylland carotenoids contentwere recorded in genotype H13-01 and H12-64 whereas minimum were in H14-04.This variation among genotypes might be due their  tolerance behaviour against temperature stress.
       
The production and accumulation of anthocyanin (ANTH) in plant tissues especially in leaves leads to development of resistance against various environmental stresses. In present investigation, among three dates of sowings, lowest anthocyanin contentwas recorded in crop sown on 15^th November and highest in December 15^th sowing at 50% flowering stage (Table 1). This variation in anthocyanin content might be due to comparatively high temperature (maximum temp. 38°C, minimum temp. 18.2°C) at 50% flowering in 15^th December sowing and low temperature (maximum temp. 17.1°C, minimum temp. 4.8°C) in 15^th October sowing resulted into more accumulation of anthocyanin. Among genotypes, highest anthocyanin was recorded in genotype H12-64 and H13-01, whereas minimum was in H14-04 and this might be due to different genetic potential of genotypes to combat with environmental stresses. Similar results also observed by Qiu et al., 2016 in tomato; Bhasker et al., 2018 in chickpea.
       
Data presented in Table 1 indicated that among three dates of sowings, lowest chlorophyll a fluorescence (Fv/Fm) was recorded in crop sown on 15^th December and highest in November 15th sowing at 50% flowering stages. This variation among sowing dates might be due to low net assimilation rate and low production of photosynthates as well as low chlorophyll contents in 15^th December and15^th October sowings as compared to 15^th November sowing at 50% flowering stages. The data in Table 1 showed that highest chlorophyll a fluorescencein genotypes was recorded in genotype H13-01 and H12-64 whereas minimum was in H14-04 this could be due to differences in leaf area and production potential of photosynthates in different genotypes. Similar results also confirmed by Basu et al., (2011); Kumar et al., (2013) in chickpea.
       
The main functions of leaves are photosynthesis, exchange of gasses and transpiration. Photosynthesis is the primary determinant of crop yield and the efficiency by which a crop captures light and converts it into biomass over the growing season is a key determinant of final yield. Leaf area and production of pigments like chlorophyll, carotenoids and anthocyanin causes enhancement in seed yield through improvement in photosynthetic efficiency. In the present investigation all the traits of chickpea leaves plays significant role in the enhancement of seed yield. The minimum seed yield were observed in plants sown on 15^th December and maximum were observed on 15^th November sown crop. This might be due to comparatively favorable climatic conditions such as temperature, photoperiod, sunshine hours and higher values of leaf area, total dry matter, photosynthetic rate and chlorophyll content in 15^th November sowing than 15^th October and 15^th December sowing. Lower seed yield during late sowing (15^th December) might be due to shorter grain filling period as a result of high temperature at grain filling stages and low temperature at vegetative and flowering stages in 15^th October sowing causes reduced yield (Table 1). Among genotypes, highest seed yield was recorded in genotype H12-64 and H13-01, whereas minimum was in H14-04 and this might be due to different tolerance behavior of genotypes against temperature stress. Similar result also reported earlier in the literature (Krishnamurthy et al., 2011; Mrudula et al., 2013; Patil et al., 2017; Bhasker et al., 2018) in chickpea and Meena et al., (2018) in cluster bean and Chaudhary et al., (2020) in Indian bean at different sowing dates.
 
Correlation analysis
 
The correlations between different leaf parameters with seed yield in 15^th October, 15^th November and 15^th December sowing dates are shown in Table 2. Seed yield was significant and positively correlated with all traits of leaf in all three dates of sowing but significant correlation was found only in 15^th October and 15^th November sowing while non-significant was on 15^th December sowing.
 

The present study showed variation in most of the leaf traits which can be exploited in various breeding programmes for the improvement of seed yield. Maximum leaf parameters and seed yield were recorded between 15^th October and 15^th November sowing, however, further delay in sowing to 15^th December, significant reduction in leaf parameters as well as seed yield were recorded. The promising genotypes identified in this study are H13-01 and H12-64 which could serve as potential source in breeding programmes for high and low temperature tolerance. These leaves traits are easy to evaluate and further can be used as best indices for screening of genotypes against temperature tolerance at other developmental stages.

The authors are grateful to the department of Botany and Plant Physiology for providing all the necessary facilities to carry out the research work.

All authors declare that they have no conflicts of interest.