Vergara - 1976 - Physiological and morphological adaptability of ri

TENIPERATLTRE AYD LIGHT. REPRODUCTIVE GROWTH AND RJPENING 187
Effects of temperature and light on
the reproductive growth and
ripening of rice
K. Munakata
SUMMARY
he effects of temperature and
light on the reproductive growth and grain yield
of rice plants were analyzed by the nonlinear multiple regression model.
data obtained annually in major rice-producing areas in Japan.
using
The number of spikelets per unit area was strongly influenced by temperature at
[~45] and [20] stage. and by solar radiation at [40] stage. The [40] means
the period of 20 days centering at 4U days before heading time. The combined
effect of temperature and solar radiation on spikelet number was most prominent
at [-40] stage. lemperature-spikelet number curves seemed to be bimodal at the
tw-o stages of [-20] and [-40]. One of the optima was 20"-23“C. and the other
was higher than 30“C.
Such phenomena were discussed in connection with tem~
perature responses of ammonilication in soil. stem elongation. and tillering.
The ripening grade. as expressed by grain yield per spikelet number. was mainly‘
govemed by the climatic factors at the two stages of [-20] and [+20]. The effect
of solar radiation was positive through the reproductive stage. while the effect
of temperature was not simple. The negative effect low of temperature on ripen—
ing grade was most severe at [-20] stage. followed by that at [H0] stage. Also, a
negative effect of high temperature was: observed around heading time. The optimum
temperature for ripening grade was 26“C at heading, followed by 23“C at
[-20] stage and 22"C at [[20] stage under nonnal solar radiation.
The time course of the multiple correlation coefficient between climatic factors
zuid grain yields had maxima at three stages: [-40]. [-20]. and [+20]. The estimation
of grain yield by the model having the parameters of light and temperature
at four stages of [-10]. [-20]. [0]. and [-20] agreed well with the actual values.
INTRODUCTION
When we analyze the response ofplant growth to climate, we should give attention
to the interaction between dry matter production and differentiation. Light
governs the differentiation and elongation of cells through photopcriodisin and
hormonal metabolism. as well as dry matter production through photosynthesis.
Also. temperature directly exerts great influence on both processes of thy matter
production and differentiation. through entire physiological and biochemical
K. rllimakala. National Institute of Agricultural Sciences. Konosu. Saitama. Japan