Genetic variability in sunflower cultivars under drought. II. Growth and water relations

Abstract

Experiments were conducted between 1981 and 1983 at Cordoba, Spain, to determine the morphophysiological basis for the differences in yield responses to drought of eight sunflower genotypes. There was genotypic variation in most characters examined, particularly in maximum leaf area and in leaf area duration, biomass accumulation and distribution, and in root water extraction. Long-season genotypes had greater leaf area and produced more biomass under drought conditions, exploring the subsoil down to 270 cm. Short-season genotypes restricted water extraction to the top 180 cm of the soil profile and had about half of the leaf area duration of a long-season cultivar. Evidence is presented of small differences in osmotic adjustment among genotypes. The relations between leaf area and grain yield as well as calculations of a carbon balance for the reproductive period suggest genotypic differences in photosynthetic efficiency under drought.