Growth and survival rate after maturity in Oryza sativa L. and O-glaberrima Steud

Ten cultivars of O. sativa (6 japonica, 2 indica, and 2 japonica X indica) and five cultivars of O. glaberrima were grown in pots. Half of each cultiv ar was cut at 10 cm above the ground at maturity, and the other half remain ed uncut. Both were grown under two different day-length conditions with a suitable temperature. The growth state at maturity, the changes in the numb er of living tillers after maturity, and the survival rate after maturity w ere examined. The starch content in the stem (stem+leaf sheath) of O. sativ a at maturity tended to be higher than that of O. glaberrima. The nodal roo t number and the total leaf length of the tiller bud from the node of a ste m section at maturity were greater in O. sativa than in O. glaberrima. New tillers appeared in both O. sativa and O. glaberrima after maturity. The nu mber of living tillers after maturity was always greater in O. sativa than in O. glaberrima, though the relation was reversed for some period in the l ong day uncut plot because of the appearance of new tillers from higher nod es. The long day and the uncut conditions enhanced the survival of tillers. In O. glaberrima, the survival rate of all cultivars at 250 days after mat urity was nil. In O. sativa, japonica cultivars were higher than indica cul tivars, including japonica X indica cultivars in the survival rate at 250 d ays after maturity. All plants of some indica cultivars had died before 250 days after maturity. The long-day condition favored the survival rate. The continued appearance of new tillers in both O, sativa and O. glaberrima af ter maturity suggested that both O. sativa and O. glaberrima had potential perennial ability. It was inferred that the perennial ability of O. glaberr ima was very small compared with that of O. sativa. It was also inferred th at varietal differences in the survival rate existed in O. sativa.