EFFECTS OF SHORT-PERIOD TREATMENTS AT LOW -TEMPERATURE (9-DEGREES-C) ON GROWTH OF RICE PLANTS AT THE TILLERING STAGE

The rice plants cv. Sasanishiki (3 plants/pot) were moved into the con trolled growth chamber at C when half of the leaf blade (LB) of the 7t h leaf (L7) was emerged (H plot) or when the whole 7th leaf blade (LB7 ) was fully emerged (W plot). The plants were kept at that temperature for 1, 2, 4, and 8 days. Plant did not grow during the treatment and began to continue the growth after treatment. In the 8-day treatment p lots (H8 and W8 plots) plants sustained heavy damage and at 1 or 2 wee ks after the treatment about 30% of plants had died.The effects of the treatments on the leaf length or on the tillering behaviour are as fo llows. 1) the length of LB and the leaf sheath (LS) treated at rapid e longating stage (LB7, LS7, LB8 of H plots and LS7, LB8 of W plots) wer e shorter than that of untreated plants, but on the other hand the len gth of LB or LS treated just before the rapid elongating stage (LS8, L B9 of H plots and LS8, LB9, LS9, LB10 of W plots) were longer than tha t of untreated plants. Tiller growth of the treated plants was slower than that of untreated plants. The percentage of emerged tillers at ex pected nodes after treatment was smaller than that of untreated plants . The percentage of emerged tillers and the tiller growth rate indicat ed the rate of the damage that plants sustained. In this study, there were no reason to say that a tiller bud was sensitive to low temperatu re in the specific developmental stage.