Abstract
Seasonal changes of tiller bud development on each successive node of orchardgrass shoot, sampled from a sward cutted 4 times a year, were investigated. 1) At the 1st cutting of 10th May 1972 (heading stage), almost all tillerbuds attached to the nodes above N8 of vegetative shoot were depressed, and 1 to 2mm in length (Fig.1). 2) Two weeks after the 1st cutting, the buds of upper nodes (N3 or N4) began rapid elongation, but the most of lower buds (N6 or below), the growth of which was inhibited during influorescence production, remained dormant. Lateral buds left in the stubble of heading shoot elongated partly after the removal of culm, however they were less vigorous and many of them died during elongation in the subtending leaf sheaths. 3) From July to early September, the development of most tiller buds of upper nodes was suppressed with increasing temperature. Most of the lowertillers, elongating or resting, lost vigour and decayed during summer depression. 4) The buds of upper nodes recovered active development as mean air temperature fell below 20℃ in the middle of September. They continued to grow normally, descending the nodal positions with the successive expansion of leaves on the mother shoot. Accordingly, tiller size was progressively larger in lower node between N3 and N8 at November 2.3 5) The tiller bud of orchardgrass may be highly sensitive to environmental conditions at the stage when the bud has just completed its organization for the further elongation. Thus some of the tiller buds grow out as fully emerged ones, and the other stay in a resting state, resulting seasonal fluctuation of the tiller population.
