(X) On forecast of the weight of 1, 000 rice-kernels. In the former report it has been made clear that weight of 1, 000 rice-kernels is determined primarily by the size of lemma and palea, and secondarily by the development of caryopsis filling up the inside of them, and, moreover, the former depend upon the environmental condition during the period prior to heading and the latter upon that after heading. Basing upon these facts, the authors have made some experiments to find out the methods for forecasting the weight of l, 000 rice-kernels. The rsults are summarized as follows: (1) As number of spikelets per head is greatly influenced by the environmental condition in the period prior to heading, weight of l, OOO kernels can be forecast roughly from the number of spikelets per head. The method is available in early stage, but its goodness of fit is not so high as the other methods. (2) Where the environmental condition in the period after heading is normal, there are found high correlation coefficients between weight of hulls and that of rice-kernels at the time of maturity, and, moreover, between weight of hulls at the time of maturity and that of hulls at the 7th day after heading. Therefore, where the environmental condition in the period after heading is normal, it will likely be possible to forecast the weight of 1, OOO rice-kernels from the weight of hulls at heading-time. (3) Whenever specific gravity of gains reaches to a certain value (the value is about 1.05, excluding grains lighter than 0.84 in specific gravity), final weight of 1, 000 rice-kernels can be forecast from the weight of developing caryopsis, irrespective of varieties, cultivating methods and stages subjected to cutting treatment of leaf-blades. Especially, it can be clearly forecast from the weight of developing caryopsis at the time when the rate of increase in specific gravity of grains begins to decrease, after reaching to its maximum rate. The period in which weight of 1, 000 rice-kernels can be forecast, so far as this present experiments are concerned, is at about 17th day for early maturing variety, 22-27th day for medium and late variety after heading.
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