水稲幼植物における剪葉が主茎および1次分げつの生長に及ぼす影響

抄録

A defoliation experiment was carried out in an attempt to clarify the interrelation in growth among the main stem and primary tillers and to determine whether or not the compensatory translocation of assimilate would occur when the leaves of main stem or some tillers were injured, in rice seedlings. The experimental material used was cultivar, Nihonbare. Plants were sown and grown in 1/5, 000 a Wagner pots outdoors at University of Tsukuba. Defoliation was carried out when the plants reached a leaf age of 7.5, at which time the tillers on the second, third, and fourth nodes (refered to hereafter as tillers II, III, and IV) had already emerged from the leaf sheaths of the subtending leaves of the main stem. Sixteen types of defoliation were performed. Leaf blades which had expanded completely were excised with a pair of scissors at the auricles, and the leaves which were still expanding were left untreated. The increment in dry weight in the main stem and each tiller for 4 days after defoliation was used as a measure of the growth. The results are summarized as follows: 1. It was assumed that the translocation of assimilate from tillers to main stem or from main stem to tillers would take place when the leaves of thc main stem or the tillers were lost, respectively, and that this kind of compensatory translocation would also occur among tillers when the leaves of a tiller were lost. 2. The fact that growth of tillers was inhibited by defoliation of the main stem and that the inhibition was severer in the upper node tillers, suggested that the growth of the upper node tiller was more closely associated with the main stem. However, tiller, II, a lower node tiller, which was considered to be at its autotrophy, might be associated with the main stem when the tiller was defoliated. 3. Considering the effect of the defoliation, growth of a tiller was influenced most by the main stem and next by the tillers below. And it was assumed that when leaves of the main stem were lost, tiller II would take the role of main stem to some extent in taking care of the other tillers, and, moreover, tiller III would take this role when both of the main stem and tiller II were injured.