Abstract:

The objectives of this study were to measure the contents of ethylene and 1-aminocylopropane -1-carboxylic acid (ACC) in rice grains and root bleeding sap during the grain filling period and the grain filling rate. Using two high lodging-resistant rice (Oryza sativa L.) cultivars grown by pot or tank with these treatments, well watered (WW), moderate soil-drying (MD), and severe water-deficit (SD) from 9 d post-anthesis until maturity. The effects of chemical regulators on the concentrations of ethylene and ACC in the grains were also studied. The results indicated that MD significantly increased, whereas SD significantly reduced, grain-filling rate and grain weight. Concentrations of ethylene and ACC in the grains were very high at early grain filling stage and sharply decreased during the linear period of grain growth. MD reduced, whereas SD remarkably increased, ACC concentrations and ethylene evolution rate. Both the ethylene evolution rate in rice grains and ACC concentrations in root-bleeding sap were significantly and positively correlated with ACC concentrations in rice grains. The ethylene evolution rate was significantly and inversely correlated with grain-filling rate. Application of amino-ethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, at 9–13 d post-anthesis significantly reduced ACC concentrations and ethylene evolution rate of the grains, whereas significantly enhanced the activities of sucrose synthase, ADP glucose pyrophosphorylase and soluble starch synthase, and the results were reversed when ethephon (ethylene-releasing agent) was applied. The results suggested that a moderate water stress during the grain-filling period of rice could inhibit the production of ethylene and ACC and therefore accelerate grain filling and increase grain weight.

Key words: Rice, 1-Aminocylopropane-1-carboxylic acid (ACC), Ethylene, Grain filling, Root-bleeding sap, Soil moisture