Agriculture Reference
In-Depth Information
30
16
A
B
14
25
12
20
10
15
8
6
10
4
5
2
0
0
10
10
20
30
40
50
10
20
30
40
50
Days after germination
A - 15 Nov. Sowing
B - 13 Dec. Sowing
Fig. 12
Low temperature changes on plant height.
workers studied the relationship between germination at low
temperature and subsequent early growth of rice seedlings.
Correlations between germination coeffi cient and plant height,
leaf length, dry weight and leaf number at an early stage of
growth were highly significant statistically (Sasaki 1986).
Positive correlation was also obtained between germination at
low temperature and root development at an early stage (Sasaki
and Yamazaki 1971). Development rate fl uctuates as a function
of air and water temperature and of photoperiod, these factors
are especially important during the vegetative phase. Cold
during this phase slows down rice development and lengthens
growth duration. Seedling discolouration is commonly
seen in indica varieties grown under low temperatures. The
discolouration is usually of various degrees of yellowing of
leaves and white bands on sheaths or white ring of entire leaves
are observed. At tillering stage, the yellowing occurs on lower
leaves. Stunting occurs at tillering stage in boro (summer) crops,
also in japonica varieties grown at 9°C and 13°C (Chamura
and Honma 1973).
