Yoshida - 1981 - Fundamentals of Rice Crop Science

CLIMATIC ENVIRONMENT AND ITS INFLUENCE 79
Table 2.7. Effect of day and night temperatures at 2 critical stages on spikelet sterility
and anthesis. a
Duration Spikelet Flowered
of low- Day Night sterility (%) spikelets
temperature temperature b temperature c (%)
treatment Booting Heading heading
(days) stage time
26 20
14
8
2.2%
8.2
11.6
10.7%
9.2
7.2
53.3%
5.0
5.0
20
3 20 14
8
4.2
7.3
15.5
9.8
8.2
8.0
8.3
5.0
8.3
20
14 14
8
5.9
11.2
23.0
6.7
8.3
5.7
11.0
0.7
0.3
20
26 14
8
3.7
6.4
22.5
9.9
19.4
41.6
95.0
36.7
13.3
20
6 20 14
8
6.1
6.6
28.0
11.5
15.5
37.4
91.7
18.3
1.7
20
14 14
8
7.0
25.8
74.8
14.6
21.1
48.3
38.3
7.0
1.3
9
26
20 4.4 12.1 100.0
14
12.1 38.7 73.3
8
48.8 71.9 75.0
20 7.4 8.5
98.3
20 14 14.4 32.3
76.7
8
52.5 73.0 16.7
20
12.9 35.4 93.0
14 14
41.3
55.6
24.0
8
76.0 85.8
2.7
a Shibata et al (1970). b 8 hours. c 16 hours.
Other experiments dealing with field crops, however, indicate that rice is most
sensitive to low temperatures at 14–7 days before heading, depending on variety
and weather conditions (Sasaki and Wada 1973). For practical purposes, 14–7
days before heading, commonly referred to as the booting stage 1 , is considered the
most sensitive stage to low temperatures. The second most sensitive stage is
heading or flowering.
1 More specifically it refers to the stage when the distance between auricles of flag leaf and penultimate
leaf is about 0 cm.