Recovery Processes after Leaf Cutting in Cereals and Forage Grasses : III. The trend of chemical constituents after defoliation in rice plants pretreated with the level of fertilization and with shading

Abstract

The rice plants previously grown under different fertilizer and light conditions were removed of their whole leaf-blades at the same time and were sampled on every 2 days thereafter to analyze dry matter production, nitrogen and carbohydrate accumulation in each organ of them. i) In HF plot, the regrowth of leaves progressed linearly with time and the weight of whole plant began to rise 4 days after defoliation, whereas in LF and SH plots, the plant weight little changed with a slight regrowth of leaves (fig. 1). 2) Nitrogen concentration of leaf-sheath and stem little changed after defoliation except LF plot where it increased. In contrast to the undefoliated plant, the nitrogen % of defoliated plants was always higher in all organs in all plots (fig. 3, 7). However the nitrogen content decreased in all organs after defoliation, thereafter being almost constant until 8 days in LF and SH plot, having begun to recover after 4 days in HF plot (fig. 8). 3) The starch concentration of leaf-sheath and stem conspicuously dropped after defoliation especially in LF plot, but that of total sugar slightly (fig. 1). Both TAC concentration and content in all organns decreased in HF and SH plots until 4 days after the treatment and then turned to increase. In LF plot they dropped more, being almost constant at lower levels until the end of the experiment (fig. 5, 6). 4) It is suggested from the results obtained that much attention should be paid to the significance of nitrogen with concomitant reserve carbohydrates in recovery of leaves after defoliation. In the earliest stage of recovery carbohydrates may play an important role, but soon nitrogen becomes a major factor determining the further regrowth.