Effect of foliar application of salicylic acid in adjustment of the effects of drought stress on some morphological characteristics and photosynthetic pigments in sunflower (Helianthus annuus L.)

Salicylic acid is one of the regulators of physiological processes causing increased resistance of plants to environmental stresses. This research was conducted with the aim of investigating the effect of drought stress and salicylic acid on morphological parameters and photosynthetic pigments in sunflower An experiment was performed as factorial in a fully random design with three replications in laboratory of physiology at Islamic Azad University, Kaleybar Branch in the agricultural year of 2017. The experimental treatments included salicylic acid at four levels (0, 0.5, 1, and 1.5 mMolar), and water potential at five levels (0, -5, -10, -15, and -20 MPa). The results obtained from the analysis of variance indicated that the interaction between drought stress and salicylic acid and level of chlorophyll-a, total chlorophyll, length, wet and dry weight of the aerial parts was significant. The results of comparing the mean of the interaction between drought stress and salicylic acid indicated that the maximum level of photosynthetic pigments and morphological parameters was obtained by the treatment involving no application of stress plus salicylic acid 1 mM. The results obtained from this research indicated that drought stress resulted in a significant reduction in the growth of aerial parts and root, wet and dry weight of the aerial parts and root, and photosynthetic pigments. On the other hand, in the plants pretreated with salicylic acid, the extent of this reduction has been modified. Based on the obtained results, salicylic acid culminated in diminished damage incurred in response to drought.