Vergara - 1976 - Physiological and morphological adaptability of ri

170 cur-airs ANT) RICE
and dropped at 50°C. Above 37°C, however, the rate decreased ivith time: the
rate at 43°C became lower than that at 3'?°C after 3 hours; lower than that at
30°C after 4 hours. The japonica-type varieties had higher respiration rates than
the indica ones.
Yamada et a1. (1955) reported that respiration increased with rising temperature
over a range from 15° to 40°C, through different growth periods. The Qw of
respiration ‘was 1.66 at nursery stage, 1.79 at tillering stage. 1.95 at ear-differentiation
stage. 206 at booting stage. and 1.89 at maturing stage for the variety
Norin 36.
Mitsui (1941) reported that the assimilation of CO, (by the fifth leaves) was
larger at 24°C than at 14°C; the plants grown at 18°C showed higher activity of
CO; assimilation at 14°C than the plants grown at 25°—29°C. On the other hand.
Matsushima et a1. (1958) reported that the amount of CO; assimilation was
approximately constant over a temperature range from 14° to 37°C (through
different growth stages).
Yamada et al. (1955) observed that the effect of temperature on the CO,
assimilation under a light intensity of 50 klux was. in generaL not clear over a
range from 18.5” to 385°C through different groiving stages; it decreased at
435°C. Under low light intensities. the assimilation increased with rising temperature
as far as 35°C; under higher intensities than 50 klux. a notable
decrease was observed even at 35°C in some experiments. Murata (1961) reported
that CO, assimilation rate decreased notably below 20°C under both
high and low light intensities.
Thus, there is disagreement concerning the assimilation at ltwv temperatures.
Herath and Ormrod (1965) reported that water temperature affected the
number and size of stomata ofriec seedlings; at a lower temperature (16°C). the
number of stomata was smaller and their size was larger than those at higher
temperatures (24° and 32°C).
Absorption and translocation
Sato (1972b) studied the effect of air temperature on the organic and mineral
composition tifrice seedlings under five day-night temperature regimes: 15°—10°,
20°—l5°_ 25°—20°, 30°—25° and 3S°—30°C. The concentrations of mineral elements
increased with rising temperature regime, except that the highest regime (35°—
30°C) tended to lower than the next range. The inhibition of nitrogen absorption
was remarkable at 35°—30°C. and the inhibition of cation uptake was remarkable
at 15°—l0° and 20°—l 5°C. Contrariwise, either the concentrations of soluble- and
protein-N or the ratio of soluble-N to protein-N increased at lotver temperatures:
l5°—l0° and 20°—l5°C. The concentrations of total sugar and crude
starch, and the ratio of total atiailable carbohydrate to nitrogen ivere higher at
lower temperatures: 15°—10°. 20°—15° and 25°—20°C. Iloshino et al. (1969)
reported that the accumulation of nitrogen and carbohydrate in seedlings is
largest at 31°C air temperature and at 16°C water temperature. These results