Barley growth,yield, antioxidant enzymes,and ion accumulation affected by PGRs under salinity stress conditions

Application of plant growth regulator (PGR) may alleviate some negative effects of environmental stresses such as salinity. A controlled environment experiment was conducted to study barley (Hordeum vulgare L. cv. Reyhane) growth, yield, antioxidant enzymes and ions accumulation affected by PGRs under salinity stress conditions at Shiraz University during 2012. The treatments were PGRs at four levels—water (as control), cycocel (CCC, 19 mM), salicylic acid (SA, 1 mM), and jasmonic acid (JA, 0.5 mM)—and four salinity levels—no stress (0.67 dS m^?1, as control), 5, 10, and 15 dS m^?1, which were arranged in a factorial experiment based on completely randomized design with four replicates. The results showed that salinity stress significantly decreased plant height, peduncle length, leaf area, ear length, grain number, dry weight, grain yield, harvest index, potassium (K⁺) accumulation, and potassium/sodium (K⁺/Na⁺) concentration ratio, which were closely associated with stress severity. However, PGRs compensated some of these negative effects, so that SA foliar application had the most ameliorative effect. Salt stress also increased Na⁺ accumulation as well as the activity of peroxidase, catalase, and superoxide dismutase (SOD). Since ion discrimination and enhanced antioxidant enzymes are associated with salt tolerance, in this experiment PGRs application might have enhanced K⁺ accumulation and antioxidant enzyme activity. The activity of SOD and K⁺/Na⁺ ratio were found to be useful in salt tolerance manipulation in barley plants.