THE DEVELOPMENT OF PLANT-TO-PLANT VARIABILITY IN MAIZE AT DIFFERENT PLANTING DENSITIES

Abstract

The development of plant-to-plant variability in dry weight components, leaf area, plant height and ear characteristics was studied by sequential sampling in a single-cross maize (Zea mays L.) hybrid grown in the field at 50 000, 100 000, 150 000, and 200 000 plants/ha. Coefficients of variation (CV) for dry weight generally increased with plant density, and were greatest for ear components. The greatest density × time interaction for the CV of dry weights of most organs occurred 1–3 wk prior to silk emergence. The CVs of plant height and leaf area per plant were little affected by density. Total shoot weight, plant height, leaf area, and floret primordia per ear row were generally normally distributed for all densities throughout the season. This contrasted, at high densities, with bimodal frequency distributions of maximum silk length and upper ear weight at flowering, and of grain yield and kernel number per plant at maturity. Frequency distributions of silk length and other flowering data indicated that florets of barren plants ceased development prior to or immediately after flowering. Bimodal frequency distributions of grain number and grain weight per plant suggested the existence of some minimum assimilation rate per plant which must be exceeded before normal grain formation occurs.