Chlorophyll a fluorescence of safflower affected by salt stress and hormonal treatments

Abstract

Salicylic and jasmonic acids are classified as stress hormones, which can affect numerous physiological characteristics of plants such as electron transporting systems in thylakoid membrane under normal and stressful conditions. A greenhouse experiment was conducted with factorial arrangement based on a randomized complete block design with three replications to assess the possible effects of salicylic acid (1 mM) and jasmonic acid (0.5 mM) on different parameters of chlorophyll a fluorescence in safflower (Carthamus tinctorius L. cv. Goldasht) under salt stress [0, 4, 8, and 12 dS m−1 NaCl (about 0, 40, 80 and 120 mM NaCl, respectively)]. Leaf chlorophyll content index, relative water content, leaf area and seed yield were decreased with increasing salinity. Salinity caused a significant decrease in the variable fluorescence, the maximum quantum yield of photosystem II, efficiency of water-splitting complex on the donor side of the photosystem II and total performance index (PItotal). The highest time needed to reach maximum fluorescence was recorded at 12 dS m−1. Maximum fluorescence and PItotal were increased, but initial fluorescence and maximum fluorescence were significantly decreased by salicylic acid and jasmonic acid treatments under saline conditions. Salicylic acid and jasmonic acid considerably improved the variable fluorescence, maximum quantum yield of photosystem II, the efficiency of water-splitting complex, PItotal, physiological parameters and seed yield under salinity. In this way, foliar application of salicylic acid and jasmonic acid could play a key role in salt stress tolerance of safflower plants.