Effect of Salicylic Acid Seed Priming on Some Physiological Traits of Cowpea (Vigna unguiculata L.) Under Water Deficit at Podding Stage

The effects of seed priming by salicylic acid on some physiological traits of cowpea (Vigna unguiculata L.) cv. Parastou were investigated under water deficit conditions at podding stage. Experiment was done as a split block design with 3 replications in 2008 at Research Station of Zanjan University. Main factor consisted of two levels of irrigation (normal irrigation and deficit irrigation at podding stages) and seed priming with salicylic acid as a sub factor in 5 levels (0, 900, 1800, 2700, 3600 µM). Analysis of variance showed that irrigation and salicylic acid had significant effects on all characters. Furthermore, interaction between irrigation and salicylic acid were significant only for leaf relative water content, photosynthetic rates, content of chlorophyll a, total chlorophyll and seed yield. Mean comparisons showed that relative water content, photosynthetic rates, content of chlorophyll a and total chlorophyll and seed yield decreased due to water deficit as compared to normal irrigation, but leaf internal CO2 increased. These traits, except leaf internal CO2 wereincreased through primed seed priming as compared to untreated seeds. Priming of seeds with 2700 µM salicylic acid had desirable effect on all traits compared to other treatments in irrigated and water deficit conditions. Seed priming with 2700 µM salicylic acid caused higher relative water content, which protects plants against water stress. In addition to increasing chlorophyll content and stomatal conductance, photosynthetic rates of plant increased. Thus, seed priming with 2700 µM salicylic acid produced highest seed yield (4424 and 2475 kg.ha-1) in both regular and deficits irrigations at podding stage, respectively.