Vergara - 1976 - Physiological and morphological adaptability of ri

RICE GROWTH IN DIFFERENT Emotions-isms 437
GROWTH PATTERNS IN DIFFERENT ENVIRONMENTS
Figure 4 illustrates the diversity of locations and seasons of rice cultivation in
Asian countries (after P. Kung. mimeo). The environment of cultivated rice
varies from place to place. from season to season at a given place. and also from
year to year at a given place and season. Although selection of varieties is made
by considering the environmental condition in which the crop is going to be
grown, the growth pattern varies considerably. Thus. various cultural practices
are used to manipulate the growth pattern to obtain maximum grain yield. In
this sense the growth pattem is the result of environment-variety-cultural
practice interaction.
Locations
Long-duration varieties cannot be grown in high-latitude areas because
of the limited season with suitable temperatures. but they are popular in
low-latitude areas for various reasons. Commercial medium-duration varieties,
however. mature in about 130 days throughout rice-grouting areas. In highlatitude
areas the vegetative growth is slow and long. whereas in towlatitude
areas it is vigorous and short. Because of this. there are more chances for
medium-duration varieties to assume Type Band Type C patterns in high and
in low-latitude areas, respectively’.
With medium-duration varieties the time from stiwing to floivering is almost
constant, but the lealing interval is shorter at higher temperatures. Thus. the
number of leaves on the main stem is greater in loxv= than in high-latitude areas.
The three leaves from the flag leaf on each stem are the ones which contribute
directly to ripening by sending photosynthates to the grains. and the number of
nodes at the base of the stem from where tillers come out is also almost constant
with a given cultural condition. Therefore, the number of nodes. from which
neither tillers nor leaves contribute directly" to ripening, is greater in low than
in high-latitude areas. The leaves from such nodes develop during the vegetativelag
phase and generally die early. Thus. there are more dead leaves and also a
larger number of excessively elongated intemodes at the base of the stem.
which results in a tall plant and a loxver grain-straw ratio in lo\v- than in highlatitude
areas.
This situation is more apparent in the tropics, because long-duration. vegetatively
vigorous varieties are more popular among farmers. Generally, the total
dryi-matter production is greater but the grain yield is not higher due to a low
grain-straw ratio.
Such a tendency was apparent in Japan 3O years ago (Ishizuka and Tanaka,
I956). In northern Japan. such as in Hokkaido, the number of leaves on the main
stern of medium-duration varieties was l2, the growth pattern was Type B. and
the grain yield was not high clue to a relatively’ small total dry-matter production,
although the grain-stratv ratio was reasonable. Due to such a growth pattern, an