Evaluation of salicylic acid efficacy on photosynthesis, gas exchange and adjustment of drought stress on medicine pumpkin (Cucurbita pepo var. Styriaca)

Salicylic acid is a phenolic compound that plays an important role in inducing drought resistance in various plant species as a growth regulator.

Methods & Materials: 

In this study, the effect of foliar application of salicylic acid on chlorophyll content, relative water content, accumulation of osmotic compounds and fruit and seeds yield of medicine pumpkin under different levels of drought stress was investigated. Experimental treatments were included the foliar application of salicylic acid at 4 levels (control (spray with distilled water), 0.5, 1 and 1.5 mg L-1) and drought stress at 4 levels (100% field capacity, 85% field capacity, 70% field capacity and 55% field capacity).

According to the present results, with increasing drought stress, chlorophyll content, stomatal conductance, transpiration rate, photosynthesis rate and leaf water content significantly decreased, however drought stress increased the amount of proline and soluble carbohydrates. These changes were accompanied by a reduction of fruit and seed yield of medicine pumpkin, so that the lowest yield was achieved under severe drought stress (55% of field capacity). Foliar application of salicylic acid by enhancing the accumulation of osmotic and protein compounds led to the mitigation of the drought stress and improved plant water status, photosynthesis and fruit and seed yield.

Based on the present results, the use of 1 mg L-1 salicylic acid is recommended to improve the yield of medicine pumpkin especially under drought stress condition.