Growth response of rice (Oryza sativa L.) to drought. I. Varietal difference in growth rate, nitrogen uptake and tillering habit at vegetative stage.

Abstract

Varietal differences in growth response to drought were studied in order to determine major attributes composing drought resistance in the rice plant. Eight rice varieties of different hydrological backgrounds (1986) were grown under soil pF 1.6 and pF 2.9, and six wetland rice varieties of different maturity (1987) were grown under flooding and soil pF 2.9 conditions for two weeks at the early growth stage, in a vinyl house. Varietal difference in response to drought was evaluatcd in terms of growth rate, nitrogen uptake and tillering habit. Varietal differences between growth and drought resistance was apparently found. RGR response resulted from the response of NGR to drought and RLGR responded in the same way as RGR and NAR. However, nitrogen uptake was more sensitive to drought than NAR then varietal response in nitrogen uptake was different from the response of RGR and NGR. Therefore, the degree of drought resistance among the varieties was evaluated according to the response of NAR and nitrogen uptake. The high tillering variety and the early-maturing variety generally tended to be sensitive to drought. However, it was found that observation of growth rate was important in evaluating drought resistance in rice because of an exceptional response. Varietal difference of hyrdrological background of rice varieties was not related to varietal difference in growth response to drought.