Abstract
The effects of two levels each of light, water supply and nitrogen and their interactions on growth and apical dominance were studied in young free-growing tea plants of clone TRI 2025 in pots in a glasshouse. The lower levels of the three factors were deliberately chosen from previous experience to be sub-optimum for good growth while the upper levels provided sufficient amounts for vigorous growth. Shade and restricted water supply reduced terminal bud activity their active phases being fewer and of shorter duration, checked the increase in height and number of leaves produced fewer, shorter, side shoots with fewer leaves compared with those of the unshaded and fully watered plants. Total leaf area leaf thickness, dry matter of leaves, stems and roots, girth of stem, relative growth rate and net assimilation rate were also reduced under conditions of shade and restricted water supply. Leaf weight ratio and shoot/root ratio were higher in the shaded plants compared with the unshaded plants but were lower under moisture stress compared with non-stressed plants and girth/length of shoot ratio was high in plants under moisture stress compared with non-stressed plants. Since shading also reduced the temperature in addition to lowering the light intensity, the effect of shade was probably due to low light as well as to reduced temperature. There was no difference in growth between the two levels of nitrogen chosen. Shade and restricted water supply greatly reduced growth, increased apical dominance and correlatively inhibited lateral bud and shoot growth. It is suggested that while adequate amounts of these factors are necessary for satisfactory growth and for the release of correlatively inhibited axillary buds their effects are mediated by changes in the levels of endogenous hormones, the relative proportions of which determine the pattern of development.
