Vergara - 1976 - Physiological and morphological adaptability of ri

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Sterile-type cool injury in paddy
rice plants
T. Satake
SUMMARY
terile-typc cool Weather injury in paddy rice plants was reviewed with special
Sreference to the studies conducted at Hokkaido National Agricultural Experiment
Station. and to ettective methods of using the phytotron.
lt had been thought that the critical period for sterile-type cool injury is the
tneiotic stage. Recently. this was precisely elucidated as the young microspore
stage. A secondary sensitive stage was found to occur just before and at the
leptotene stage of meiosis.
The critical temperature for sterility is approximately l5“‘-20°C. This sterility
is primarily due to injuries occurring in anthers.
A number of physiological abnormalities became perceptible 4-5 days after
the cooling. Tapetal hypertrophy is observed as early as on the second day of the
cooling. and abnormalities of microspores on the foimh day. An increase in
sucrose in anther cells is also detected on the second day‘. These facts indicate that
the initial injury of coolness in anther cells is the disturbance of carbohydrate
metabolism.
INTRODUC TION
Cool injury in Hokkaido
Rice was originally a plant that grew in the tropical region. Nowadays it has
been grown over a wide range of latitude from 49°N to 35°S within which daily
and seasonal regimes of temperature and day length vary widely In a temperate
region such as Japan, only varieties weakly sensitive to photoperiod have been
cultivated, and the length of the growing season is mainly limited by low ternperaturc
in the early spring and late autumn. In the northern regions of Japan.
especially" on the island 01' Hokkaido, rice yields have often been decreased by
cool weather in summer. Figure 1 shou-‘s the trend of paddy lice yields in Hokkaido
for the past 90 years. T\\-'eiit_v-t\\~'r: of 90 years (approximately one in four)
were love-yield years due to cool temperature in summer. Cool injury of rice
plants has been a problem of economic importance in Hokkaido, and many
experiments have been done to solve the problem. As shown in Fig. l, there
T. Sarcike Hokkaido Agricultural Experiment Station, Hitsujigaoka, Toyohira-ku. Sapporo. Japan.