1988 Volume 57 Issue 4 Pages 636-642
The objective of this study was to examine whether the ripening period is affected by water stress during early stages of panicle development in rice. Sixteen seedlings of a paddy field rice cultivar Koshihikari were transplanted in a 4l pot containing sandyloam soil, and pots were kept flooded. Tillers being removed weekly, only main culms were exposed to 10 different soil moisture stress started either at the primary rachis branch or the floret differentiation stage. The time from sowing to heading increased by water stress. The panicle growth after heading was lowered by water stress and the ripening period was shortened when water stress became severe. As a result, the growth period varied only slightly under water stress. Although a proportional relation existed between the time from sowing to heading and water stress duration, this was not so chose as to cumulative water stress (CWS). It is therefore concluded that the ripening period of rice is shortened under water stress during early stages of panicle development, while the time to heading increases with increasing CWS. The causes of shortening the ripening period and its contribution to grain production were discussed.
