Geoscience Reference
In-Depth Information
poverty. The cultivation of rice extends from dry lands to wet-
lands and from the banks of the Amur River at 53° north latitude
to Central Argentina at 40° south latitude. Rice is also grown
in cool climates at altitudes of over 2600 m above sea level in
the mountains of Nepal, as well as in the hot deserts of Egypt.
However, most of the annual rice production comes from tropi-
cal climate areas. In 2004, more than 75% of the global rice
harvested area (about 114 million out of 153 million ha) came
from the tropical region whose boundaries are formed by the
Tropic of Cancer in the Northern Hemisphere and the Tropic
of Capricorn in the Southern Hemisphere (Nguyen, 2005). The
temperature increases, which results in rising seas and changes
in rainfall patterns and distribution, and may affect the land and
water resources required for rice production and achieving the
desired productivity of rice crops. The highest limit of tempera-
ture for growth of rice is 45°C and temperatures above this will
be adverse for yields. The optimum temperature range for rice
at different stages after germination is 35-31°C whereas for rip-
ening it is 20-29°C (Table 8.1). The temperature may affect and
produce abnormal symptoms in rice (Table 8.2). Such a rapid
increase during the crop growth stages, particularly during
extremely sensitive reproductive and early grain-filling stages
of rice (
Oryza sativa
L.), leads to reduced biomass, grain yield
and quality. Hence, increasing diurnal temperature tolerance in
table 8.1
Critical temperatures for the development of rice
plant at different growth stages
Critical temperature (°C)
Growth stages
Low
High
Optimum
Germination
16-19
45
18-40
Seedling emergence
12
35
25-30
Rooting
16
35
25-28
Leaf elongation
7-12
45
31
Tillering
9-16
33
25-31
Initiation of panicle primordia
15
−
−
Panicle differentiation
15-20
30
−
Anthesis
22
35-36
30-33
Ripening
12-18
20-29
>30
Source:
From Yoshida, S. 1978.
Tropical Climate and Its Influence on
Rice
. IRRI Research Paper Series 20. Los Baños, Philippines,
IRRI.
