Yoshida - 1981 - Fundamentals of Rice Crop Science

14 FUNDAMENTALS OF RICE CROP SCIENCE
Table 1.5. Growth rate of IR8 at different temperatures up to 5 weeks after sowing. a
Mean Growth rate Ratio of growth rate
temperature
0-1 wk 1-2 wk 2-3 wk 3-5 wk 0-1 wk 1-2 wk 2-3 wk 3-5 wk
(°C) (mg/plant (g/g (g/g (g/g
per wk) per wk) per wk) per wk)
22 8.1 1.16 1.16 1.40 1.0 1.0 1.0 1.0
25 10.7 1.53 1.40 1.50 1.3 1.3 1.2 1.1
28 13.7 1.51 1.35 1.62 1.7 1.3 1.2 1.2
31 15.7 1.52 1.39 1.62 1.9 1.3 1.2 1.2
a Yoshida (1973a).
dominate growth. During this week the seed reserve supports more than 70% of
growth, and the breakdown of the seed reserve is enzymatic.
Temperature influences growth less after the first week. Relative growth rates
are about the same at 25°, 28°, and 31°C after the first week, and 22°C is considered
subnormal for seedling growth. These results indicate that 25°–30°C is best for
seedling growth. Growth may be reasonably good up to 35°C, above which it
declines sharply. Above 40°C seedlings may die. The critical minimum tempera-
1.11. The effects of temperature on cell division and cell enlargement
of the cortex of the radicle tip (Yamakawa and Kishikawa
1957).