The annual ryegrass (Lolioum multiflorum) was used in this study. The seeds of ryegrass were germinated in a growth chamber at 20±1℃, with 60% to 80% of humidity, under 12h light (400 lx)/12h dark. The continuous illumination was provided by cool-white fluorescent lamps (400 lx). When the second or the fourth leaves fully expanded the normal leaves were selected for the experiments. SNP ([Na_2Fe(CN)_5]·NO, Merck, Karmstadt, Germany) was used as NO donor. In the experiments the stock solution of 10mmol/L SNP...