Studies on the Assimilation and Translocation of <SUP>14</SUP>CO<SUB>2</SUB> in Ladino Clover : IV. Utilization of reserve <SUP>14</SUP>C-assimilates by the plants in the early stages of regrowth

Abstract

To determine the length of time in which newly developing organs depend upon reserve assimilates for their growth, the following experiments were carried out. Ladino clover plants were exposed to 14CO2 for 2 hours in an assimilation chamber. After 48 hours all plants were completely defoliated, selected plants were harvested at the time of defoliation and others were harvested 1, 3, 6, 9, 12, 15 and 18 days later. (The mean temperature during the experiments was 16.9°C). Harvested plants were radioautographed and the radioctivity of leaves which had developed since defoliation was measured with a gas flow counter. The experiments were performed 3 times. The major results and interpretation are as follows; 1) The specific activity of 14C in emergent leaves decreased rapidly in the first 6 days. and decreased slowly thereafter. This indicates that developing leaves depended on reserve assimilates only for about six days in these experiment. 2) Total activity of 14C in newly developing leaves continued to increase until 15 days after defoliation. In other words, reserve assimilates continued to translocate into the leaves until about two weeks after defoliation. 3) These result, together with those previously reported (Proc. Crop. Sci. Soc. Japan 36:269-274), indicate that emerging leaves are dependent upon reserve assimilate during their first week of development. Although they continue to utilize resesves during the second week, the young leaves are themselves exporting essimilates during this period and presumably are no longer dependent upon reserves.