DROUGHT RESISTANCE OF BRACHIARIA SPP. I. PHYSIOLOGICAL ASPECTS

Abstract

The effects of drought stress on stomatal conductance, leaf water potential, leaf proline content and both shoot and root biomass was
studied in four grasses: Brachiaria decumbens cv Chontalpo (BD), Brachiaria brizantha cv Insurgente (BB), and the hybrids CIAT 36060
and 36061. The experiment was conducted under greenhouse conditions in 2002, where two drought treatments were applied at the vegetative and reproductive stages (80 and 100 days after sowing, respectively), in addition to an irrigated control. During vegetative stage, drought stress significantly (P≤0.05) reduced stomatal conductance by day 10, while in the reproductive stage of CIAT 36061 stomata remained open for a longer time under drought. Plant water potentials were statistically different (P≤0.05) between drought treatments, among genotypes and for the interactions of both factors. Proline accumulation showed statistical differences (P≤0.05) between drought treatments and among genotypes, the hybrid CIAT 36061 having the lowest proline accumulation in both stages. Statistical differences (P≤0.05) in biomass production were found between drought treatments and the two hybrids had the highest root dry matter production. The hybrid CIAT 36061 was the most drought resistant variety and had also the highest root shoot biomass ratio.