Studies on Growth and Functions of Root System in Tea Plants : V. Changes in carbohydrate, amino acid and nitrogen contents during the process of root regeneration after root pruning

Abstract

This experiment was conducted to clarify the relation between the process of root regeneration and changes in some chemical components in root-pruned teaplants (Camellia sinensis (L.) O. Kuntze cv. Yabukita). The growth of top and roots, and TAC (total available carbohydrate), total amino acid and nitrogen contents were investigated over about six-month period after the root pruning. About a half of root of one-year old plants were pruned in early September 1983 (Fig. 1). The top growth was prominently retarded by the pruning. The weight of top (including the mother stem) in the pruned plants was reduced to nearly 75% of that in the intact plants (Table 1). In contrast, the root growth was activated after the pruning. The weight of roots was markedly increased. especially in wite roots. At the 36th day after the pruning. the root of the pruned plants rather exceeded in weight that of the intact plants. The remarkable increase in the white roots on the mother stem was recognized within 36 days succeeding the pruning, while that on lignified roots required one month after the pruning. The percentage of the white roots in the treated plants was around 10% higher than that in the intact plants. Although the T/R ratio of the treated plants had been considerably raised due to the pruning, it returned to approximately the same level as that of the intact plants at the 26th day (Table 2). The pruning not only raised the TAC content, but the partition of the TAC to the mother stem and roots greatly increased (Figs. 3, 4). Furthermore, the pruning increased the partition of nitrogen to the mother stem and roots, in spite of a deterioration in content (Figs. 5, 6). The amino acid content in the treated plants showed a lower level as compared with that in the intact plants. The amino acid content of lignified roots greatly decreased following vigorous regeneration of roots (Fig. 7). The distribution of the TAC and nitrogen in the treated plants, however, approximately accorded with these in the intact plants after 187 days. The above results suggest that the root regeneration after the pruning in tea plants rapidly proceeds through active growth of white roots exceeding the growth in the intact plants. The translocation of some chemical components to under-ground parts and the accumulation there that were induced by the root pruning were considered to closely concern with the root regeneration. The retardent of the top growth following the root pruning was estimated to be induced by the translocation of substances to roots and vigorous regeneration of roots. To promote the root regeneration after the root pruning, treatments that maintain a proper level of hormons and relieve the deficit of photosynthate and nitrogen are necessary.