1979 Volume 29 Issue 4 Pages 294-304
To evaluate what physiological factors are responsible for the year-to-year fluctuations of heading time in field, heading response to temperature under natural daylerigth (Y) and the three factors controlling heading time i. e. thermo-sensitivity (X1)' photo-sensiti-vity (X2), and basic vegetative growth (X3) were investigated for 44 paddy rice varieties. The former was determined by growing plants in growth cabinets, the air of which was kept at a lower or higher temperature .by a given degree than the open air. Item Y was expressed by the delay. in heading time caused by a temperature difference of 1.5°C at very high (+3.5∼+1.5), high (+1.5∼±0), Iow (±0∼1.5) and very low (-1.5∼-3.O) temjerature range. The latter three factors wereobtained by grdwing plants under daylength (10h, 14h) and constant temperatures (20°C, 30°C). X1, X2 and X3 were expressed by nSL-nSH, nSL-nLL, and nSH, respectively, where nSL, for instance, stands for the number of days frorn sowing to heading under the condition of short photoperiod (10h) and low temperature (20°C). Multiple correlation between Y and a set of Xl, X2 and X3, and partial regression. of Y on the three variabies we.re calculated.
