Agriculture Reference
In-Depth Information
Table 7 Effect of low temperature on ∝-NA oxidation of rice roots (12ºC).
Variety
Days after
Treatment
-NA oxidation
(mg/2 hrs./g
dry root)
Reduction as
% of control
Control -NA
oxidation (mg/2
hrs./g
dry root)
IR8
5
2.013 ± 0.111
61.4
5.210 ± 0.184
10
1.214 ± 0.084
77.8
5.473 ± 0.171
15
0.751 ± 0.077
86.7
5.654 ± 0.163
20
0.414 ± 0.097
92.9
5.821 ± 0.225
Mean
1.098
5.539
much more signifi cant than air temperature for early growth
and development of low land rice (Hoshino et al. 1969). This is
because the growing points of the plants are under water.
Shoot elongation at early seedling stage ranges from 7°C to
16°C and that for root elongation from 12°C to 16°C (Nishiyama
1977). Hence about 10°C may be considered as the critical
minimum for elongation of both shoot and root (Table 8). The
optimum temperature for cell division of the radicle tip is 25°C
and that for cell enlargement 30°C. Elongation of the radicle
stops below 15°C.
Favourable temperature range for physiological processes of
rice plants is from 15°C-33°C. However, the growth of roots has
an optimal temperature around 25°C and lower temperatures
Table 8 Growth of rice seedling.
Variety
Seedling
Length (cm.)
No. of Leaves
Seedling dry
weight (g)
Cont.
LT
Cont.
LT
Cont.
LT
IR58025A
27.7
13.8
3.56
3.00
0.027
0.017
Giza181A
18.7
13.6
3.36
3.00
0.024
0.022
IR58025A
X Giza181A
24.5
11.2
3.50
3.00
0.023
0.014
Mean
23.6
16.2
3.47
3.00
0.025
0.018
(after Abdelkhalik et al. 2010)
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