Yoshida - 1981 - Fundamentals of Rice Crop Science

76 FUNDAMENTALS OF RICE CROP SCIENCE
2.7. Relationship between 1,000-
gram weight and mean temperature
for 2 rice varieties (Yoshida
and Hara 1977).
2.3.4. Air vs water temperature
Lowland rice, grown in flooded soils and varying water depths, is inevitably
affected by water temperature.
The basic principle governing which temperature, air or water, affects rice
growth more is the position of the growing point with respect to water depth
(Tsunoda and Matsushima 1962).
Until the initiation of panicle primordia, the growing points of leaves, tillers,
and panicles are under water, and water temperature affects growth and develop-
Table 2.5. Effect of light and temperature on grain growth of
IR20 and Fujisaka 5 rices. a
Grain Filled Ripening
Light b Temper- wt d (W) spikelets (F) grade e
ature c (mg) (%) (W × F)
IR20
Low Low 15.5 65 1014 ( 71)
Low High 14.8 62 910 ( 64)
High Low 16.3 87 1423 (100)
High High 16.0 86 1370 ( 96)
Fujisaka 5
Low Low 22.0 86 1890 ( 90)
Low High 20.4 84 1718 ( 82)
High Low 23.0 91 2102 (100)
High High 21.9 92 2013 ( 96)
a Yoshida and Hara (1977). b Low: 36 cal/cm 2 per day PAR (photosynthetically
active radiation), High: 114 cal/cm 2 per day PAR.
c Low: 23/15°C, High: 32/24°C. d LSD value at 5% level is 0.2 for
both varieties. e Figures in parentheses indicate relative values
with 100 as the maximum.