Experiments conducted in a controlled environment showed that after 3 weeks
of early growth, the relative growth rate of variety IRS was not much affected by
temperature within the daily mean range of 25º to 31ºC (Yoshida, 1973b). Likewise,
a shading experiment in the field demonstrated that solar radiation during
a 25-day period after transplanting did not have any significant overall
effect on yield and yield components (Table 2, Fig. 6). Therefore, within the
range of variation at Los Baños, it is reasonable to conclude that variation
in daily mean temperature and solar radiation during the vegetative stage does
not affect spikelet number per square meter