Agriculture Reference
In-Depth Information
3
VEGETATIVE GROWTH
Rice is a low temperature-sensitive crop especially during
seedling, tillering, panicle development and fl owering stages,
which can be easily injured by cold treatment. Most of the
high-yielding varieties do not perform well, the reduction
in seedling growth of rice due to low temperature is one of
the major problems in tropical and subtropical areas at high
altitude as well as areas where cold mountain water is used
for irrigation. In subtropical areas the summer rice also suffers
from cold during early growth.
Tanaka and Yamaguchi (1969) studied the effect of
temperature on the early growth of seedlings. The growth
rate increased with increasing temperature over a range from
20°C to 30°C.
After seedling emergence, the root structures in young
seedlings show higher weight proportions than shoot and hence,
soil temperature also affects their growth and development.
Nishiyama (1977) reported that the critical minimum
temperature for shoot elongation ranged from 7 to 16ºC and
the root elongation from 12 to 16ºC. The critical minimum for
elongation of both shoot and root is, hence, about 10ºC. Depending
on the cultivars, seed history and cultural managment practices,
these critical temperatures may vary (Table 5).
