Abstract
Corn (Zea mays L.) hybrids are often selected for near optimal conditions of water availability, yet frequently are grown under less than ideal soil moisture. Different responses among corn hybrids to drought stress have been observed, but the physiological and morphological differences that confer drought resistance or susceptibility are not well understood. The objective of this study was to identify differences in leaf water relations, stomatal activity, and root length density distribution between two corn hybrids known to differ in their response to water stress. During the 1983 and 1984 growing seasons, two corn hybrids (Pioneer Brands 3192 and 3165) were subjected to three water management treatments: irrigated, rainfed, and stress during vegetative (1983) or reproductive (1984) growth. During periods of water stress, hybrid 3192 wilted 2 to 3 days sooner and maintained leaf water potentials (ΨL) and leaf turgor potentials (Ψp) that were 0.2 to 0.5 MPa and 0.1 to 0.3 MPa lower, respectively, than those of hybrid 3165. Water stressed plants of hybrid 3192 closed their stomata earlier during periods of water stress, but the relationship between leaf diffusive resistance and Ψp was similar for both hybrids, with stomata beginning to close as Ψp decreased below 0.4 MPa. Regardless of the stage of ontogeny, hybrid 3165 always maintained a lower Ψp at a given ΨL than hybrid 3192. However, the primary difference observed between the two hybrids was the ability of hybrid 3165 to simply avoid tissue desiccation by maintaining higher ΨL and Ψp. The deeper rooting profile of hybrid 3165 may have contributed to the maintenance of higher ΨL and Ψp during water stress. Copyright © .