Effects of ascorbic and salicylic acid foliar application on physiological traits of two chickpea cultivars (Cicer arietinum L.) under drought stress conditions

Chickpea (Cicer arietinum L.) is the third most important food legume. Drought is one of the main constraints restricting the growth and yield of crop plants. Most chickpea producing areas are in the arid and semi-arid zones, and approximately 90% of world’s chickpea is grown under rainfed conditions. The water deficit stress condition decrease chickpea yield and produced biomass. If the drought stress lasts long, the plant will face the oxidative damage inevitably, and can be resulted in producing reactive oxygen species (ROS) which are the result of incomplete reduction of oxygen. It is suggested that antioxidants, like salicylic acid (SA) and ascorbic acid (AA), may enhance drought tolerance in plants. Salicylic acid is one of the antioxidants which prevent the high activity of ROS and is introduced as an important messenger molecule in plant responses to different biotic and abiotic stresses. It is reported that ascorbic acid increases the cell division and causes increasing dry and fresh weight of leaf on plants and also antioxidant decreases the damage from oxygen radicals produced due to drought stress. The purpose of this research was to study the effects of SA and AA foliar application on physiological traits of two chickpea genotypes under different drought stress conditions. In this study the effects of drought stress and foliar application of salicylic acid and ascorbic acid on different characteristics of chickpea including seed yield, seed protein content, leaf relative water content and photosynthetic pigments were investigated in Agriculture and Natural Resources Research Station of Sanandaj. The experimental layout was a split plot factorial as RCBD with four replications. Four levels of water stress were considered arrangement in main plots including: Complete irrigation as control, Drought stress at vegetative stage, Drought stress at reproductive stage, and Drought stress at vegetative and reproductive stages. Combination of chickpea cultivars (ILC482 and local landrace) and ascorbic acid (100 mg/l) and salicylic acid (200 mg/l) were allocated to subplot. All the experimental plots from sowing to branching were fully watered to achieve a proper stand establishment. Foliar spraying of the plants was performed when the fifth lateral branch emerged. Plots were irrigated by a drip irrigation system. Soil moisture content was measured by gravimetric method and thus the volume of water applied to each plot was determined. Transparent plastic covers over the plots were used to avoid the effects of periodic rains and then removed when the rain stopped. Accumulated rainfall and irrigation were determined in four levels of irrigation. The measured data were analyzed statistically by analysis of variance operations using the SAS computer package version 9.1. Means of treatments were compared by Duncan’s multiple range test at the 0.05 level of significance. Results showed that drought stress reduced seed yield, biomass, hundred-seed weight, relative water content, leaf protein content, concentration of chlorophyll a and b, carotenoids and total chlorophyll. The mean seed yield of chickpea under the stress treatments of vegetative, reproductive and continues stress was decreased at the ratios of 53, 63 and 68% respectively as compared with control. In well watered conditions, photosynthesis rate and assimilates production are increased which consequently results in the elevation of seed yield through increasing in seed filling rate and seed weight. Moreover comparison between the recorded yields in vegetative and reproductive stress treatments revealed that the yield reduction in reproductive stress treatment was more pronounced compared to vegetative stress, indicating the vulnerability of chickpea yield to terminal drought stress prevailing and occurring at reproductive stage of chickpea development. Terminal drought stress is considered as a primary constraint to chickpea productivity in countries such as Iran, where the crop is generally sown after the main rainy season and grown on stored soil moisture. The results indicated that ascorbic acid application resulted in the increase of seed yield, chlorophyll a, carotenoids and total chlorophyll. Results also indicated that application of salicylic acid increased the amount of chlorophyll a content. Whereas hundred-seed weight and leaf relative water content were not affected by growth regulator substances. Results showed that drought stress decreased agronomic and physiological characteristics in this study. Generally it was concluded that SA and AA have the potential of diminishing injury effects of drought stress and promoting crop productivity. Results also indicated that application of ascorbic acid and ILC482 cultivar are suitable in climatic conditions of Sanandaj.