Vergara - 1976 - Physiological and morphological adaptability of ri

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Microclimate of the rice crop
Z. Uchijima
SUMMARY
he radiation environment of the rice crop is illustrated in relation to its stmcture
giving special attention to complementary difiusc radiation produced by
the scattering of light from plant leaves‘ Wind records are used to elucidate the
acrody-‘namical characteristics of the rice crop in relation to plant growth and
wind, The intensity of air mixing in thc rice crop diminishes very rapidly with increasing
depth from the top of the canopy. because leaves abstract momentum
from the llow by skin trictiisn and fonn drag.
Temperature regimes in water and soil layers afllecting the growth and the yield
of rice are analyzed using the heat-balance method. The influence of a plant canopy;
on energy partition of fields is described on the basis of observations in rice fields.
Measured CO, profiles are compared with those simulated for a model rice
canopy. The profiles of photosynthesis by sunlit and shaded leaves in the rice crop
are presented to compare their respective contributions to canopy photosynthesis.
Effects of radiation flux and air mixing on the cantipy photosynthesis of the rice
crop are described.
INTRODUCTION
Crop vegetation significantly" modified thc exchange of cncrgy and mass bctween
the canlfs surface and the atmosphere and makes a canopy environment
in which crop plants live from genninatitin to maturation, Growth and yield of
a crop are substantially affected by the canopy microclimatc as well as by
weather conditions. Therefore, there is a need for a study to elucidate quantitatively
the turbulent transfer process of atmospheric constituents such as
sensible heat, water vapor. and carbon dioxide, and the partition process of
radiant energy among leaves. Research during the past decade has revealed that
the turbulent exchange of atmospheric constituents and the supply of adequate
radiant energy to the site of photosynthesis are fundamental processes which
control the canopy microclimatc. These two processes arc closely rclatcd, in
turn. to the spatial and vertical Iistribtition of plant elements, particularly
leaves within the crop canopy
In this review, measurements obtained mainly in canopies of lowland rice are
used to illustrate the microclimate of the rice crop, because more information
Z. (Jchijmia. Division of bteteorology, National lttststute of Agricultural Sciences. Tokyo. Japan.