Time of Flowering Affects Grain Quality and Spikelet Partitioning Within the Rice Panicle

Anthesis of spikelets in the panicle of a tall indica rice cultivar, Kajalghara, was completed within a period of 7 days. Development progressed in basipetal fashion from the spikelets of the uppermost primary branch of the panicle to the lowermost. According to the timing of onset of anthesis, spikelets of the panicle were segregated into seven groups. Dry mass accumulation and starch and assimilate (soluble carbohydrates and amino acids) contents of each group were studied from anthesis to grain maturity. Spikelets that anthesed earlier produced better quality grains and also had higher sink efficiency in converting soluble assimilates into reserve structural matter than those which anthesed later. These results rule out deficiency in supply of assimilates as a cause of partial filling of grains in the rice panicle. The study also emphasises the need for improving the percentage of high density grains in the rice panicle to maximise the use of available assimilates and enhance the grain yield potential of the plant.