Tolerancia temprana a la competencia intra-específica en maíz: efectos sobre el crecimiento, el desarrollo reproductivo y la fijación de granos.

CELA, S.; MADDONNI, G.A.; OTEGUI, M.E.

Rosario, Santa Fe, Argentina

Congreso; VIII Congreso Nacional de Maíz.; 2005

Asociación de Ingenieros Agrónomos del Norte de la Provincia de Buenos Aires (AIANBA)

Maize response to overcrowding has been widely studied, and the establishment of hierarchies among plants (i.e. dominant and dominated individuals) has been identified. It is known that, at stand densities near the optimum, grain yield is limited by kernel abortion of pollinated ovaries and not by incomplete flower development at silking. There is no evidence, however, of presilking limitations to ear reproductive differentiation at supra-optimal stand densities. Because maize grain yield improvement has been based on an enhanced tolerance to increased crowding, the objective of the present work was to study the effect of supra-optimal stand densities on reproductive development of extreme plant hierarchies. It was an objective of this research to determine if grain yield of dominant and dominated plants grown at high stand densities is exclusively limited by a restriction in growth or if there is an additional effect attributable to an impaired development (i.e. morphogenetic arrest). For this purpose, two hybrids of contrasting tolerance to overcrowding were grown in the field at a stand density of 120000 pl ha-1. Plant growth, reproductive development and kernel set were characterized for the different plant hierarchies. From 500 ºCd onwards, dominated plants of both tested hybrids had a smaller biomass than dominant individuals. The different plant growth rate between extreme hierarchy groups was reflected in the anthesis-silking interval per plant, and the period of silk emergence per ear. The reduced kernel number per plant of dominated individuals was not conditioned by potential number of florets per ear. A delayed silk extrusion and a larger abortion of pollinated ovaries determined the low kernel set of dominated plants.