Studies on Branching Habits in Crop Plants. : VIII. Varietal differences of tillering ability of rice plants under controlled conditions varied in light intensity and temperature

[摘要] Heavy-tillering (panicle number type) varieties, Kinmaze and Akibare, and poor-tillering (panicle weight type) varieties, Koganenishiki and Norin No. 22 were grown under natural condition, and Kinmaze and Koganenishiki were grown under controlled conditions varied in light intensity (47, 000 lux and 15, 000 lux) and temperature (30°C and 20°C) in phytotron. 1. Number of tillers was largest under low temperature (20°C) with strong light (LT-SL) and smallest under high temperature (30°C) with weak light (HT-WL). Under high temperature with strong light (HT-SL), abnormal yellowing of leaves took place, and some primary tillers died during the growth. Varietal differences in number of tillers were recognized under natural condition and every condition in phytotron except HT-SL. Under good conditions such as the outdoors and LT-SL, varietal differences in number of tillers were large in secondary and tertiary tillers and small if any in primary tillers. Under worse conditions, however, varietal difference was remarkable in all kinds of tillers, and under the worst condition it was remarkable rather in primary tillers than in secondary tillers. From these results, a model was proposed to explain the varietal difference in reference to environmental condition. 2. The regression equations of leaf age "y" (age of a shoot expressed by number of emerged leaves) of the primary or secondary tillers to the leaf age "x" of their respective mother culms were calculated (y=ax-b). There was no varietal difference at all in regression coefficient under natural and every controlled condition, although some differences due to the conditions and numbers (locations) of the nodes on which the tillers occured were observed. No varietal difference was recognized in the value of "x" when "y"=1 (roughly at this leaf age the tiller appears out of the leaf sheath of the mother culm). 3. The appearance ratios (see Table 4) of the tillers on lower or upper nodes of mother culm in Kinmaze were larger than those in Koganenishiki under every controlled condition. 4. From above results, the varietal difference in number of tillers is thought to be caused by the difference in appearance ratio of tiller on each node (especially on lower and upper nodes) of mother culm.

[学科分类] 农业科学（综合）