Rate and Duration of Growth of Kernels Formed at Specific Florets in Spikelets of Spring Wheat 1

In an earlier study, large differences in individual kernel weight were observed within spikelets of spring wheat genotypes ( Triticum aestivum L. em Thell). To account for these differences, growth rates and effective filling periods were measured in field experiments for kernels formed at each floret position in central spikelets. The genotypes ‘Era’, ‘8037’, and ‘72316’, which differed in kernel weight and kernel number per spikelet, were used. Kernels formed in the fourth and fifth florets (numbered from the spikelet base) displayed significantly lower growth rates than proximal kernels during the period of linear kernel dry matter accumulation. Kernel growth rates during this period over all years, genotypes, and floret positions were significantly correlated with final individual kernel weights. Another factor that influenced kernel weight within a spikelet was the earlier occurrence of anthesis in the proximal florets compared to distal ones. Kernels formed in proximal florets already had a considerable weight advantage even before the period of linear dry matter accumulation. Effective filling period durations of proximal kernels of Era and 72316 were longer, a probable consequence of the earlier anthesis in these florets. Cessation of dry matter accumulation (and the associated sharp decline in kernel water content) were judged to occur at approximately the same time for all kernels in a spikelet. Additional research oriented toward understanding those factors responsible for establishing kernel growth rate during the linear dry matter accumulation period is advocated.