Vergara - 1976 - Physiological and morphological adaptability of ri

STERILE-TYPE COOL INJURY I.\I PADDY RICE PLANTS 283
Owen (1971) stated that eool injury in the tropics resulted from the spread of
dryr-season culture. which has been made possible by using high-yielding. photo»
period-nonsensitive varieties together with development of water storage. Thus.
cool injury 01' rice plants has now become an important problem common to
rice-growing countries in both temperate and tropical regions.
Kaneda (1972) classified eight types of cool injury‘ based on answers to the
questionnaire. They are failure in germination, slow seedling growth. stunting,
discoloration, paniele tip degeneration, prolonged duration, sterility‘, and irregular
maturity’. Types of coo] injury‘ and their significance to rice yield were
diverse due to differences in the rice-growing season. elevation, latitude. rice
cultural technology‘. and so on. Iligh sterility, delayed heading, and irregular
maturity were types common to every country.
Two types of cool injury in Hokkaido
In Japan there are two types of eool injury‘: sterile-type (destructive type) and
delayed-growth type. ln the sterile type. severe decrease in yield results from
sterility caused by‘ unseasonable cool temperature at the booting stage or at
anthesis. In the delajved-groivth type, low yield results from grain immaturatioil
caused by cool temperature during the maturing period. Improvement of varieties
and cultural methods have made it possible to reduce eool injury of the
delayed-growth type to some degree. On the rather hand. technical improvements
designed to control sterile-type injury‘ are still insufficient. and severe damage
cannot be avoided today. A phytotron was built at the Hokkaido National
Agricultural Experiment Station in 1966 to help make clear the mechanism of
cool injury (Yamamoto. 1970). We have been making physiological studies on
the mechanism of sterility by use of this phytotron.
Satake(l949. 1971a. 1971b. 1972a, 1972b) havealreadv reviewed studies on the
sterile-type cool injury in Japan. and Ishizuka et al. (1973) discussed the general
aspects of studies on eool injury in Hokkaido. This review will deal primarily‘
with the recent advances in physiological studies on sterile-type eool injury‘ in
Japan with special reference to the studies at Hokkaido National Agricultural
Experiment Station.
HISTORICAL REVIEW OF STUDIES
ON SIERILEJFYPE COOL INJURY IN JAPAN
It has been well known for many years that rice yield decreases are due to sterility
in years ivith unseasonably‘ coo] summers. Ilowever, until the mid-l930's it
had not been understood which of climatic factors during the growth stage
induced sterility‘. Akemine and lloshika (1939) statistically‘ analyzed the relation
of sterility to meteorological factors by using experimental data from 32 varieties
of rice plants for l4 years (1923-1936). They found that air temperature induced
sterility‘. and that light intensity and humidity did not. Since this early‘ report,
studies of eool injury‘ in rice plants have been conducted mainly on the effect of
cool temperature on sterility