Abstract:
Effect of air temperature on duration of spikelet opening and rate of grain filling of
five rice varieties; At307, Bg300, Bg305, Bg358 and Bg359 of different seed sizes
were studied at Rice Research and Development Institute (RRDI), Batalagoda.
Spikelet opening duration was lowest in Bg300 and higher in Bg358 and Bg359.
Mean thermal time , requirement (GDD) from spikelet opening to completion of
anthesis of a panicle was significantly higher in Bg358 and Bg359 than At307,
Bg300 and Bg305. At307 recorded the highest GDD to mature from heading.
Bg300, At307 and Bg305 showed higher initial grain filling rate than Bg358 and
Bg359. Individual panicles of Bg300, At307 and Bg305 completed grain filling in a
shorter duration than other varieties. If an adverse climatic condition which occurs
within shorter period, the probability of spikelet fertilization of the whole panicle of
Bg300, At307 and Bg305 is much lower than Bg358 and Bg359. Varieties having
higher grain filling rate require better environmental conditions during that period
than varieties with longer grain filling period. Thus, Bg358 and Bg359 are more
adaptable to sudden changes in adverse environmental conditions than that of
Bg300, Bg305 and At307.
