Abstract
Elongation and dry matter yield of shoots of napiergrass (Pennisetum purpureum Schum., cv. Merkeron), in the vegetative stage of growth, were compared between the plants sprayed with distilled water and those sprayed with a growth retardant. The retardant used was 0.538% (w/w) solution of paclobutrazol, and the treatment was done when the plant height was about 1 m. The lengths of lamina and sheath of several unfolded leaves and of about ten internodes above thc phytomer of the uppermost unfolded leaf at the time of the treatment, were shorter, and their leaf widths were larger in the treated plants than in the control. The increase of shoot numbers was enhanced by the treatment. The ratio of dry matter yield of the treated to that of the control was 1.262 for lamina, 0.712 for stem with leaf sheath, 1.274 for dead parts and 0.940 for whole shoots when the whole shoots yield of the control was in the range from 10 to 20 t ha-1. Thus, the suppression of shoot elongation brought about such a disadvantage in the process of roughage production as the reduction ot whole shoots yield. This disadvantage, however, was partially compensated by the improvement of forage quality in terms of leaf/stem ratio of yield.
