Vergara - 1976 - Physiological and morphological adaptability of ri

PHYTOTRONS IN AGRICULTURAL RESEARCH l)
Duration of groin filling ldoys)
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Temperature ("Cl
2. Effect of temperature on the duration of grain filling
in four cultivars of wheat. Solid symbols. grain titling in
winter; open symbols. grain tilling in summer (Sofield.
Evans. and Wardlatv. I974).
which fell rapidly as radiation increased, suggesting a relatively constant total
input radiation for the period of grain filling. Ilo\ve\-'er, experiments under
controlled conditions have shown that incident radiation as such had no effect
on the duration of grain filling, Whereas temperature had a pronounced effect
(Fig. 2). The apparent effect of radiation in field experiments is presumably due
to correlated changes in temperature.
The pronounced effect of high temperatures in shortening the duration of
storage has also been found in experiments with cotton (Baker et al. 1972). and
may be common to many crop plants. The small increases in rate of storage at
high temperatures by no means compensate for the reduced duration, and this
effect is likely to impose a major limitation on yields in the tropics. With wheat,
we are still unclear as l0 what hastens cessation of grain grotrth at high temperatures.
lt is certainly not lack of photosynthetic assimilates. but it may involve a
breakdown in the transport system to the grain. because there is an abrupt
cessation of water uptake by the grain when its growth ceases.