Physiological Responses and Antioxidant of Wheat Cultivars in PGR -Mediated Alleviation of Drought Stress

Abstract

Drought is one of the most important abiotic stresses and factors limiting the successful production of plant products worldwide and has adverse effects on plant growth and other metabolic processes. The role of exogenous individual or combined application of Silicon (Si) and Cycocel (CCC) (control, 3.6gL-1 Si, 210mgL-1 CCC, and 3.6gL-1 Si + 210mgL-1 CCC) on grain yield and some key physiological characteristics of wheat (Triticum aestivum L.) cv. Gascogen (drought-sensitive) and Aflak (drought-tolerant) was investigated under field water-stress conditions (100% and 40% field capacity). Drought stress caused a considerable reduction in biological yield, yield and yield components, relative water content and leaf water potential of both cultivars. Application of Si and CCC effectively improved these parameters in water-deficit treatments. Moreover, water-limited conditions markedly promoted the activities of key antioxidant enzymes including peroxidase, ascorbate peroxidase, catalase and superoxide dismutase as well as the levels of Malondialdehyde (MDA) and hydrogen peroxide (H2O2), while enhancing the accumulation of soluble sugars, potassium, magnesium and calcium in leaf tissues. Application of Si and CCC further enhanced the activities of the key antioxidant enzymes and accumulation of osmolytes, and decreased the levels of H2O2 and MDA in drought stressed plants; the positive effects of Si were greatest when it was applied with CCC. Synergistic effects of Si + CCC application on yield and physiological parameters were apparent compared with Si or CCC applied separately water-stress alleviation and yield improvement in the wheat cultivars by Si and CCC application was attributable to partly improved osmotic adjustment and antioxidant activity as well as to more favorable water status under stress conditions. Overall, Si and CCC application proved to have great potential in promoting grain yield of wheat in drought-prone areas.