INFLUENCE OF PLANT HEIGHT AND OF LEAF NUMBER ON MAIZE PRODUCTION AT HIGH PLANT DENSITIES

This experiment was conducted in Ames, Iowa, US, with the purpose of v erifying if reduction in plant height, through the use of dwarfing gen es, or leaf number, by growing short season genotypes, can be a useful strategy to reduce barrenness and improve maize tolerance to drought and high plant population stresses. Five genotypes were tested: a full season hybrid, a short season hybrid, and three dwarflines, containin g the homozygous recessive genes d3, br2 and d1. Each genotype was pla nted at four plant populations: 25,000, 50,000, 75,000 and 100,000 pla nts ha(-1). There was no significant drought stress during the entire growing season of 1994. High plant population decreased number of grai ns per ear of dwarf lines and did not affect this variable for hybrids . Consequently, differences in yield between hybrids and dwarves were greater at the higher plant populations. Inbreeding depression, unimpr oved genetic background and poor plant architecture limited the respon se of dwarf grain yield to the increase in plant population.