Vergara - 1976 - Physiological and morphological adaptability of ri

429
Comparisons of rice growth in
different environments
A. Tanaka
SUMMARY
is a phenomenon resulting from the cnvironmcnt-iraricty-cultural
Growth practice interaction. lt is a sequential development of vegetative, reproductive.
and ripening phases. As the climatic environment of rice cultivation is extremely
diverse due to diversity of the location and season in which rice is grown.
there are various types of growth patterns.
The ideal growth pattern is a balanced vigor throughout a smooth succession
ot‘ the three growth phases. Varieties and growing seasons should be selected to
take advantage of climatic resources at their maximum efficiency. and cultural
practices should be selected to make the grou-‘lh pattern ideal by filling thc gap
between the nature of varieties and environmental conditions.
An agroecologieal interpretation of grovrth is a tool to synthesize information
obtained from experiments conducted in well-controlled. but artificial. conditions
into a practical rice-cultivation technology,
ENVIRONMENT
In this paper EIIVWOITIIIQITT means the “natural climatic environment." ic, the
complex of seasonal sequential changes in the combination of climatic factors
occurring in nature. and “agronomic modification." i.c. the cultural practices
uscd by fanners to improve the crop. with economic profit.
Day length is short in winter. gradually becomes long in summer. and
decreases again gradually until winter. and this seasonal change is greater at
higher than at lmvcr latitudes. Day length has a strong influence on the groivth
duration of rice plants. depending upon their sensitivity to photoperiod. No
practical effort. however. is being made by farmers to change the day length for
rice cultivation.
Air temperature changes Wlllt the season. and soil or i-vatcr temperatures
change accordingly. The annual mean temperature decreases. as a rule. from
lower to higher latitudes, and also from lmver to higher altitudes. In temperate
areas the temperature is low in spring. increases in summer, and dccrcascs
again in autumn". the duration of a season suitable for grovring rice is limited.
Thc seasonal change is generally gradual, ‘out sometimes sudden changes result
from irregular weather fluctuations; and a large fluctuation of seasonal change
A. Tanaka. Faculty of Agriculture. Hokkaido Llniversit)’. Sapporo. Japan.