Ethylene production by the flag leaf and panicle and their effects on grain quality in rice (Oriza sativa).

Ethylene is a plant hormone that regulates several physiological processes, such as, senescence of leaves and ripeness of inflorescence in cereals. The aim of this work was to determine if ethylene is involved in rice grain ripeness and its culinary quality. AVG (aminoethoxyvinylglycine) and Ethephon (chloroethylphosphonic acid) were sprayed on different rice plots cv. Yeruá P.A. from anthesis to grain ripeness. Ethylene production was quantified in both, panicles and flag leaves. Chlorophyll content, as a senescence index, was measured on the latter. Grain culinary quality was evaluated by calculating the starch amilose percentage and by recording starch gelatinization temperature. Ethylene production increased during flag leaves senescence and panicle ripeness in all plots. The amilose percentage also increased significantly in grains treated with AVG and Ethephon, while gelatinization temperature did not decrease significatively in both treatments. These results showed that ethylene might play a rol in rice grain quality.

Key words: amylose, rice, grain quality, ethylene, gelatinization temperature.