Exogenous nitric oxide alleviates shade-induced oxidative stress in tall fescue (Festuca arundinacea Schreb.)

Summary

Nitric oxide (NO) is an important signalling molecule involved in a diverse range of physiological processes. In this study, the effects of sodium nitroprusside (SNP), a donor of NO, on the growth and anti-oxidant capacity of leaves of tall fescue [Festuca arundinacea (Schreb.) cv. Arid3] were investigated under low shade (LS), moderate shade (MS), and heavy shade (HS) applied for 7 d and 14 d in all cases. LS plants exhibited slight injury, while MS and HS caused a significant increase in cell membrane damage throughout the stress period, which was measured by enhanced electrolyte leakage (EL) and increased malondialdehyde (MDA) concentrations. Exogenous application of 0.1 mM SNP alleviated this oxidative stress, increased leaf widths and chlorophyll (Chl) concentrations, and decreased leaf lengths in plants grown under shade stress. Spray applications of of 0.1 mM SNP also increased the activities of the anti-oxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX), and the accumulation of proline in stressed leaves. Significant increases in endogenous NO concentration were found in tall fescue leaves after 7 d and 14 d of shade. SNP-treated plants grown under shade stress produced higher concentrations of NO than untreated, shaded plants. The application of SNP was more effective at reducing the detrimental effects of shade stress on tall fescue leaves under MS than under LS or HS stress. These results suggest that one or more of the breakdown product(s) of SNP might be signalling molecule(s) which enhance the activities of anti-oxidant enzymes and increase proline concentrations to alleviate oxidative damage in the leaves of tall fescue plants grown under shade stress.