水稲の同化産物配分に関する研究 : 第3報 窒素施用時期の差が水稲のモミワラ比におよぼす影響

抄録

Application of nitrogen at different growth stages varied the total dry weight at the ear emergence and at maturity. The early application of nitrogen increased the total dry weight and straw weight at the ear emergence and at maturity much more than late ones. But the dry weight of ears at maturity and the grain yield had not always definite relation with the time of application of nitrogen. In case of the time of application of nitrogen being different, the dry weight of ears at maturity had not always definite relation with the dry weight produced after the ear emergence nor the number of spikelets, in spite of it being strongly affected by them. Except the treatment applied nitrogen after the rate spikelet initiation stage, the dry weight of ears at maturity was positively correlated with the dry weight produced after the ear emergence. But in all the treatments applied nitrogen after the late spikelet initiation stage, the dry weight of ears at maturity was positively correlated with the number of spikelets. So, the dry weight of ears at maturity was determined by the inter-relationshp of the number of spikelets and the dry weight produced after the ear emergence as reported previously. Dry weight of shoots increased after the ear emergnce was represented as the difference of the dry weight produced after the ear emergence and the dry weight which ears needed. The number of spikelets was determind by the interrelationship of the amount of nitrogen absorbed by the late spikelet initiation stage and that absorbed during the period from the late spikelet initiation stage to the ear emergence as reported previously. And the dry weight produced after the ear emergence was positively correlated with the product of the amount of solar radiation during the ripening period by the sum of the amount of nitrogen in leaf-blades at the ear emergence and the amount of nitrogen absorbed after the ear emergence. So, the dry weight of ears and shoots, the dry weight ratio of ear to shoot at maturity could be represented as a function of the amount of nitrogen absorbed at different growth stages. In this experiment, the dry weight ratio of ear to shoot had not definite relation with grain yield, the percentage of ripened grains and the amount of carbonhydrates in shoots at maturity, respectively. So, it could not always be taken as the index of the diagnosis of the yield, the percentage of ripened grains and the translocation of carbohydrates from shoots to ears, but could be taken as the index of the diagnosis of the interrelationship of the dry weight production at different growth stages and the number of spikelets, or the index of diagnosis of the interrelationship of nitrogen absorbed at different growth stages.