Protective roles of nitric oxide on antioxidant systems in tall fescue leaves under high-light stress

Abstract

Nitric oxide (NO) is an important molecule involved in many physiological processes. In this study, the effect of NO on oxidative damage caused by high levels of light was investigated in tall fescue leaves. Tall fescue was developed in relative low light intensity (100 mol m-2 s-1) for 21 days and then transferred to high light (500 mol m-2 s-1). Tall fescue leaves was supplied with NO donor, sodium nitroprusside (SNP), before high-light treatment to determine the physiological mechanisms of NO on
tall fescue tolerance to high-light stress. Treatment of tall fescue leaves with 100 M SNP before highlight stress resulted in alleviated light-induced electrolyte leakage, malondialdehyde and carbonyl contents in tall fescue leaves. The levels of H2O2 and superoxide radical ( ·- 2 O ) were reduced as well. Moreover, the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) increased in tall fescue in presence of SNP under high-light stress. This pattern was reversed by application of NO scavenger, 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) before light treatment. Pronounced increases of NO production were found in tall fescue leaves after exposure to high-light stress. The results suggested that high-light stress elevated NO level and
that NO might act as a signalling molecule to enhance antioxidant enzyme activities, further protecting against injuries caused by high-light stress.