| |
| This study tested the hypothesis that abscisic acid (ABA) and ethylene may mediate the effect of postanthesis soil-drying on grain filling of rice (Oryza sativa L.) through regulating antioxidative systems. Two rice cultivars were pot-grown, and three soil-drying treatments, well-watered (WW), moderately soil-drying (MD) and severely soil-drying (SD), were imposed from 9 days post anthesis until maturity. Levels of ABA and ethylene, activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), and contents of superoxide anion (O2-) and malondialdehyde (MDA) and their relationships with grain filling rate were investigated. The results showed that, when compared with the WW treatment, the MD treatment increased, whereas the SD treatment decreased, grain filling rate and activities of CAT, POD, and SOD in both superior and inferior spikelets. Both MD and SD treatments increased contents of ABA, superoxide anion and MDA in grains, with more increases under the SD than under the MD. The MD treatment decreased, whereas the SD treatment increased, ethylene evolution rate and 1-aminocycopropane-1-carboxylic acid (ACC) content. The ratio of ABA to ACC (ABA/ACC) was the highest under the MD and the lowest under the SD among the three soil-drying treatments. ABA content, activities of CAT, POD, SOD, and ABA/ACC very significantly and positively, while the levels of ethylene and ACC and contents of superoxide anion and MDA significantly and negatively, correlated with grain filling rate. Application of cobalt ion (inhibitor of ethylene synthesis) or ABA at early grain filling stage significantly decreased contents of superoxide anion and MDA, and increased activities of CAT, POD, SOD and grain filling rate. Spraying with ethephon (ethylene-releasing agent) or fluridone (inhibitor of ABA synthesis) had the opposite effect. The results suggest that an increase in ABA and decrease in ethylene in the grains under postanthesis moderate soil-drying could enhance the activities of antioxidative enzymes and reduce free radicals in grains, and therefore, accelerate the grain filling rate of rice. |
|
| Keywords:Rice (Oryza sativa L.); ABA; Ethylene; Antioxidative enzymes system; Grain filling; Soil-drying |
|
