Yoshida - 1981 - Fundamentals of Rice Crop Science

48 FUNDAMENTALS OF RICE CROP SCIENCE
1.40. Relationship between development time and mean temperature
for the period, as compared with the temperature
summation model for the relationship (from Weather and Life
by Lowry, W. P., 1969. Used with the permission of Academic
Press).
adverse temperatures cause a lengthening of the time required for development.
The actual response of the plant to temperature is curvilinear while the temperature
summation concept assumes a linear relationship.
The foregoing example indicates that there is no linear relationship between
temperature and growth duration. This nonlinearity seriously limits the use of
temperature summation.
The entire growth process from germination to maturity includes many component
physiological and biochemical processes. Some processes may be temperature
insensitive, others may be linearly dependent on temperature, and still others
may be logarithmically dependent on temperature. Thus, the implicit assumption
of the temperature summation concept that growth rate or developmental rate is a
linear function of temperature is an oversimplification.
Temperature control of growth duration in photoperiod-insensitive varieties is
understood on the basis of the following:
(i) A rise in temperature increases the rate at which leaves emerge.
(ii) The number of developed leaves on the main culm before heading is fairly
constant for a given variety.
(iii) As a result of (i) and (ii), the number of days from sowing to heading is
fairly constant under a given temperature regime.
(iv) A rise in temperature increases the rate of grain filling after flowering.