J Integr Plant Biol. ›› 1962, Vol. 10 ›› Issue (2): -.

• Research Articles •    

A Dynamic Analysis of Grain Weight Distribution During Maturation of Rice

Wang Tian-duo   

Abstract: 1. The supply of photosynthates to the rice panicles was increased by providing more light through thinning or diminished by stripping off the leaves at the time of flowering. The rate of grain weight increase varied accordingly. Samples of panicles are taken every week thereafter, and grain weight distribution was determined by weighing single grains. 2. All the distribution patterns of grain weight after the grains begin to fill have at least two peaks, one of them is at 4–5 mg, representing empty hulls. As growth proceeds, the peaks of the larger grains merge into one of about 30 mg, i.e. the weight of full grain. The photosynthates are neither evenly nor randomly distributed to all grains. In plants with artificially enhanced and diminished photosynthate supply the proportion of empty and full grains differs markedly, while the weight of the single full grain remains similar. 3. When the data was calculated and plotted in another way with time, weight class and accumulated frequency (expressed as percentage) as the three axes, it can be shown that in plants with cnhanced photosynthate supply most of the grains increase in weight simultaneously, while in plants with diminished photosynthate supply a large portion of grains remain nearly empty. 4. These results showed that under conditions of unequal pbotosynthate supply the number of grains which do not fill to any marked extent varies in such a way that most of the grains which begin to increase in weight may get enough photosynthates to develop normally. It is a typical case of the regulatory ability of the rice plant to ensure fully grown grains under unfavourable conditions. 5. There is a hierarchical order among the grains on the panicle. The difference between them is not always one of degree; in cases of insufficient photosynthate supply, some of the grains gain not merely less weight than the dominant ones but practically none at all. The response of grain filling process to the amount of photosynthates available is very likely one requiring a threshold value of the stimulus to take place. This phenomenon must be taken into account in considering the mechanism of grain filling.

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