Vegetative growth and soil water extraction of two maize hybrids during water deficits

Abstract

Identification of specific physiological differences between maize hybrids tolerant and susceptible to drought would be useful to plant breeders for improving selection criteria. One approach to identifying physiological differences is to compare cultivars differing in response to water-deficits. In this study, three field experiments focused on vegetative growth were conducted to evaluate differences between two maize ( Zea mays L.) hybrids (Pioneer Brand Hybrids 3165 and 3192) with similar growth patterns but known to differ in their response to water deficits. The hybrids were compared under water-deficit conditions on the basis of visual ratings of stress symptoms, photosynthetic rates, leaf area index, soil-water extraction and biomass accumulation during vegetative growth. Hybrid 3165 consistently had less visible signs of stress and higher photosynthetic rates under stress than did hybrid 3192. In two of the three experiments, however, overall biomass accumulation was significantly less for hybrid 3165 compared to hybrid 3192, and there were significant differences in biomass only at early sampling dates. No significant differences in soil-water extraction were found in any of the three experiments. Nonetheless, a consistent trend observed in the soil-water extraction data indicated that hybrid 3165 plots initially had a slightly greater soil water content than hybrid 3192 plots. The differences between these two hybrids were apparently due to the slightly slower early growth of hybrid 3165 that resulted in the conservation of soil water, which in turn delayed the onset of stress effects. These results highlight the importance of comparing cultivar physiological responses to water deficits at equal soil water contents.