Relation of the number of shoot units with or without crown roots to the characters of the top in the ripening stage of rice plant.

Abstract

The number of shoot units with crown roots, which is related to the number of crown roots per stem, and the number of shoot units without crown roots, which bore close relation to the finishing time of crown roots elongation, differed among rice cultivars having the different number of leaves on the main stem. Accordingly, the number of shoot units with or without crown roots was investigated in relation to the characters of the top in the ripening stage. Examined were the number of living leaves per stem, leaf area per hill, chlorophyll content, stomatal aperture and dry weight of the top. Better characters of the top were exhibited in the rice plant having more numerous shoot units with crown roots in such experiments as cutting-off the uppermost-positioned crown roots of 2 or 3 shoot units (Exp. 2) and moulding up the lower part of stems to accelerate rooting from relatively high-positioned shoot units (Exp. 3). But, the rice plant which was transplanted at the leaf age 5.5 did not show better characters of the top than that transplanted at leaf age 8.5 (Exp. 1), although it had more numerous shoot units with crown roots than the latter. The number of shoot units without crown roots was less in the plots in which the characters of the top were better in Exps. 2 and 3, while that number was approximately equal between two plots in Exp. 1. From these results, it was proved that the characters of the top in the ripening stage were not always affected by the number of shoot units with crown roots, but they had a close relation with the number of shoot units without crown roots.