The Effect of Population Density on Floret Initiation, Development and Abortion in Winter Wheat

There is little information in the literature concerning thephysiological basis of the relationship between plant populationdensity and kernel number in winter wheat (Triticum aestivumL.). Thus, two experiments were conducted to evaluate this relationship.Expt 1, involving three population densities, was carried outnear Taian, China in 1982 and in Expt 2, two densities wereevaluated near Lexington, Kentucky in 1986. Plants were sampled every 2 d in the spring, main stem spikeswere dissected and florets were scored according to a 10-stagescale of development. The rate of primordia initiation increasedas density increased until the point at which primordia numberswere equal in all treatments. After this point, an increasein density reduced the primordia initiation rate. In both experimentsincreasing density reduced the total number of floret primordiainitiated and the number of kernels per spike. In Expt 1 theeffect of density on kernel number per spike was accounted forapproximately equally by the effect of density on number ofprimordia initiated and floret abortion. In Expt 2, however,floret abortion was influenced much less by density and accountedfor only 7 % of the variation in kernel number per spike. Thekey result was that the effect of density was determined earlyin floral development. The data suggest that yield losses athigh densities may be determined too early in development tobe offset by N applications at the terminal spikelet stage. Triticum aestivum L., spike development, spikelet development, seeding rate