Intra-specific competition in maize : kernel growth of extreme plant hierarchies.

TANAKA, W. AND MADDONNI, G.A

Seattle, Washington

Congreso; ASA, CSSA, SSSA Annual Meeting; 2004

ASA, CSSA, SSSA

In maize (Zea mays L.) there is little information of plant hierarchy effect on grain growth. The objective of our research was to analyze the evolution of kernel weight and their fractions (i.e. pericarp, endosperm and embryo) of extreme plant hierarchies. Two hybrids of contrasting response to crowing (tolerant: DK752 and susceptible: DK765) were cropped at a supra-optimal population density. Final kernel weight and kernel fractions did not differ among hierarchies neither among hybrids (ca. 243 mg). The lag phase of both hybrids concluded 177 degree days after female flowering, and the shorter effective grain filling period of DK765 was compensated with it higher effective grain filling rate (0.042 vs 0.038 mg per each 100 degree days).The pericarp growth dynamic did not differ among hybrids, beginning near flowering and concluding at 430 degree days after flowering, when grains normally present their maximum water content. Both the endosperm and the embryo began to grow at 210 degree days after flowering, and concluded at physiological maturity, but endosperm presented a constant relative rate of growth (i.e. to the maximum weight of the endosperm) in comparison with the bi-phase evolution of embryo growth. In future works the chemical composition of the different fractions of the grain will be analyzed.