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Comparative Physiology and Water Relations of Two Corn Hybrids During Water Stress¹

The responses of several physiologlcal processes to water stress imposed at three stages of growth were compared in two corn (Zea mays L.) hybrids. One hybrid (XL62AA) was a good drought tolerant commercial hybrid, while the other was an experimental hybrid (LH) derived from a cross of two Latente parents. The hybrids were compared to assess their relative responses to water stress. The LH hybrid exhibited higher rates of leaf photosynthesis than the XL62AA hybrid, but only at high leaf water potentials. Photosynthetic rates of both hybrids decreased as leaves aged. The LH hybrid maintained higher levels of soluble sugars and starch in the leaves as water potentials declined, perhaps owing to higher photosynthetic rates and/or reduced sink demand for photosynthate.The concentration of abscisic acid was also higher in the LH hybrid particularly when plants became waters tressed. Comparisons of the internal water relations between the hybrids indicated that differences in the leaf turgor-leaf water potentlal relationship existed only during the time tassels were emerging. During this period, the LH hybrid maintained higher turgo pressures at all leaf water potentials compared with the XL62AA hybrid. When stress was imposed during the time of rapid leaf expansion and the told-grain filling stages of development the leaf turgor-leaf water potential relatlonships were similar in the two hybrids. The LH hybrid exhibited certain physiological characteristics that may allow greater drought tolerance or resistance when compared with a good drought tolerant commercial hybrid. As such, the LH hybrid may represent an important source of germplasm for developing more drought tolerant hybrids.

Key Words: Latente • Leaf conductance • AbA • Photosynthesis • Drought acclimation

² Central Research and Development Dep. Exp. Stn., E. I. du Pont de Nemours and Co., Wilmington, DE 19898.

Received for publication March 25, 1982.