Recovery Processes after Leaf Cutting in Cereals and Forage Grasses : IV. Some physiological changes in rice plants following defoliation

Abstract

Physiological changes induced in rice plant following defoliation were studied from 1961 to 1968. In the defoliated plants, the water and nitrogen content (%) increased with a concomitant increase in transpiration per unit weight of shoot as compared with those of the untreated control (fig. 1, 2). Recovery was most rapid in leaf formation and nitrogen absorption with the reduction of carbohydrate content in the stem and leaf-sheath (fig. 3). The Total-N/TAC ratios of shoot, therefore, were higher in the defoliated plant (fig. 4), indicating a more juvenile state. Chlorophyll content was also higher in the treated plant with a higher photosynthesis (fig. 7, 8 table 1). During 10 days following defoliation, the root activity expressed in the ability of TTC reduction was lower due to the stoppage of new root formation. After that, however, as the new roots emerged and elongated, the activity of the treated plant surpassed that of the control the roots of which were becoming gradually less active (fig. 9, 10). Higher growth rate in the later half-life of the defoliated plant was considered to be caused by the physiological juvenilization induced from the later formation of new roots and their longer persistence.