Vergara - 1976 - Physiological and morphological adaptability of ri

PI-IY'SI(JL(')F1ICAL AND .\I(‘)RPI-I(JL(')F1I{‘.»\I. ADAPTABILITY 67
Physiological and morphological
adaptability of rice varieties to climate
B. S. Vergara
SUMMARY
is a major crop that is planted in a variety of environmental conditions. "the
Rice wide adaptability of rice to climatic tactors has been possible through the incorporation
of the follovring characters in the present varieties;
insensitivity" to day length. which facilitates planting of rice at any time of the
year and at different latitudes of the tropics and subtropics.
Tolerance to low temperature. so that varieties can be planted at higher altitude
and higher latitudes.
Shorter plant height and erect leaves. resulting in better utilization of solar radiation
and better response to nitrogen lertiliZer.
Drought resistance or ability to recover from moisture stress. an important
requisite for rainfed rice culture.
Specific adaptability‘. such as ability to elongate in deep water; resistance to certain
problem soils.
As higher grain yields are expected in the marginal areas. i.e. upland areas. acid
sulfate soils. frequently submerged areas. deep water areas, low temperature areas,
etc. and more such areas are being planted to rice. further increase in the adaptability
of a wide selection of rices is needed. Several methods are being used or
proposed. Still the main drawback is the lack of testing methods for specific and
wide adaptability.
New agronomic practices may he tried to increase the suitability of rice varieties
to other areas. In the long run, however. altering the genotype might be a
better method of increasing adaptability, rather than changing the environmental
conditions.
INTRODUC TION
Rice is a major crop that is planted in the most diverse eiwirtinrnental conditions;
from sea level to 3,000 m altitude in Nepal. from 35° S in Australia to
49° N in Czechoslovakia (Kratochvil. 1956). Temperatures and day lengths arc
therefore quite diverse in the rice-growing areas. Rice is also grown under different
n=atcr conditions. from mcsoxcric conditions to deep watcr reaching up to
5 meters. Rainfall is an important climatic factor in the culture of rice since it is
the main source of Water in most of the rice-groiving areas.
Thcrc arc vcry fcw studies on the adaptability of ricc to different climatic
conditions per se. There are. hovt-‘ever. numerous studies on the effect of tem-
B. S. Vcrgara. Plant Physiology Department. International Rice Research Institute (IRRI). Los
Bafms. Laguna. Philippines.