Nitric oxide counteracts the senescence of detached rice leaves induced by dehydration and polyethylene glycol but not by sorbitol
2002
Cheng, F.Y. | Hsu, S.Y. | Kao, C.H.
In the present study, we evaluated the protective effect of nitric oxide (NO) against senescence of rice leaves enhanced by water deficit. Dehydration (DH), polyethylene glycol (PEG) and sorbitol (ST) treatments were used to induce water deficit. Senescence of rice leaves was determined by the decrease of protein content. NO donors [N-tert-butyl-alpha-phenylnitrone (PBN), sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1), and ascorbic acid + NaNO2] were effective in inhibiting senescence of dehydrated and PEG-treated rice leaves, but had no effect on senescence of ST-treated rice leaves. PEG or DH resulted in a marked increase in malondialdehyde (MDA) content and decrease in superoxide dismutase (SOD) activity, but ST had no effect on MDA content and SOD activity. Treatment with NO donors caused a reduction of PEG- and DH-induced increase in MDA content and decrease in SOD activity. The protective effect of NO donors on promotion of senescence, increase in lipid peroxidation and decrease in SOD activity induced by PEG and DH was reversed by 2-(4-carboxy-2-phenyl)-4,4,5,5- tetra-methylinmidazoline-1-oxyl-3-oxide, a NO specific scavenger, suggesting that the protective effect of NO donors is attributed to NO released. The inhibition of PEG- and DH- enhanced senescence of rice leaves by NO is most likely mediated through increasing SOD activity and decrease in lipid peroxidation.
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