GROWTH OF AN ANNUAL STRAIN OF ORYZA-GLABERRIMA STEUD AND A PERENNIAL CULTIVAR OF ORYZA-SATIVA L AFTER HEADING

The growth of W492 (an annual strain of Oryza glaberrima Steud.) and Koshihikari (a perennial cultivar of Oryza sativa L.) after heading were compared to determine the growth characteristics of annual and perennial types in the genus Oryza. The plants were grown individually in 1/5000a pots. At heading and every week thereafter, 10 plants of each strain were sampled. The dry matter and the starch content of each plant part were determined. Greater differences were found between W492 and Koshihikari in: (1) the rate of dry matter accumulation in the panicle; (2) the rate of decrease of leaf area; (3) starch content of stem + leaf sheath and (4) new shoot emergence after heading. There was no marked difference in the harvest index between the two strains, which is typically a distinguishing characteristic between annuals and perennials. In the aforementioned differences, (3) and (4) have already been reported as differences between annuals and perennials but (1) and (2) have not. Based on these results, we assume that monocarpic annuality is closely associated with faster dry matter accumulation in the panicles and faster leaf area reduction. More extensive experiments using many annual and perennial strains are needed to confirm our assumption.