Desirable traits for tropicalisation of wheat II. does the maturing wheat grain self-regulate its internal temperature vis-a-vis the post-anthesis temperature stress?

A late maturing cv. C 306 and an early maturing cv. Raj 3765 of wheat (T. aestivum) were exposed to higher post-anthesis ambient temperatures by delaying the sowing of both the cultivars by one month. Comparative changes in the post-anthesis temperature of the maturing wheat grains of the two wheat genotypes were measured by point sensors, using the semiconducting device called ‘Thermister’. The results suggest the existence of a thermoregulatory machanism which seems to be most effective during active phase of dry matter accumulation in the maturing grain, irrespective of the genotypes. The earliness in the better performer Raj-3765, appears to be associated with enhancing the growth process, and thereby, shortening the grain maturation period, as an adaptation under late sown conditions. This seems to be induced by maintaining relatively higher temperature of the maturing grain. However, the tolerant genotypes (C-306) was indeed more efficient in maintaining the internal temperature of the grain with in a narrower range, through a mechanism involving down regulation. The efficiency of the mechanism of thermoregulation, in turn, seems to be linked with the active period of synthesis in the maturing grain, possibly through the regulation of the partitioning of the electrons to alternative oxidase pathway.