Studies on growth and function of root system in tea plants. III. Influences of root pruning on development of root system and function of white roots.

Abstract

Influences of root pruning treatment on shoot and root growth were examined, using young tea plants (Camellia sinensis (L.) O. Kunsze cv. Yabukita). Morphological and functional properties of new roots (white root) were investigated from December to the following July, using 4-year-old plants treated in late August. Relationship between root growth and yield, and root pruning were studied by the different methods (5 times and intensities) of root pruning. High aged and thick roots generated numerous white roots after decapitated by root pruning (Table 1.). The white roots grew more thickly and long than these on intact roots in the control plot, showing poor curvature and branching (Fig. 2). The white roots showed a high level of the activity by TTC reduction and uptake rate of nitrogen during winter season. But, thereafter, their both functions steeply lowered during the first crop season, so that fell below the similar roots in control plot in the successive summer crop season (Figs. 3, 4). The white root, however, maintained the activity of apex and respiratory rate that exceeded the similar roots in the control plot over the whole experimental period (Figs. 3, 5). This suggests that the deterioration in their some functions during and after the first crop season partially attributes to morphological properties, namely, poor branching and so on. The root pruning caused a decrease in lignified root despite treatment times (Jul. to Nov.) but induced 10-40% increase in white roots except the treatment in late November, so that percentage of the white root to total root weight rose by 10-20% relatively to the control plot (Fig. 6, Table 3). The most excellent regeneration of roots was observed in 40-60% root pruning plots (Fig. 7). In the first crop season after root pruning, total shoot weight per plant compared poorly with the control plot regardless of treatment times (Table 4). From the results above, appreciate root pruning was concluded to be effective to induce active growth of roots and to rejuvenate root system. Crop productivity has been also estimated to annually rise with development of the rejuvenated root system although that considerably decreased in the first year following to root pruning treatment.