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Interactive Effects of Nitrogen and Water Stresses on Water Relations of Field-Grown Corn Leaves¹

Water and N stresses often limit corn (Zea mays L.) grain yields. Although the effects of either water or N stress on crop growth and development, physiology, and yield have been widely studied, relatively little information is available on the interactive effects of these stresses when imposed in combination. The objective of this study was to define and evaluate the interactive effects of water and N stresses on leaf water potential components, transpiration rate, and stomatal resistance of field-grown corn leaves. Corn grown on a Kendrick fine sand soil (loamy, siliceous, hyperthermic Arenic Paleudult) was subjected to two water management treatments (optimal irrigation, and a 10-day water stress period, which immediately preceded 50% silking). Within each water management treatment, two N levels (low, 62 kg ha^–1; high, 275 kg ha^–1) were imposed. During the water stress period, both midday and diurnal measurements of leaf water potential (_L)leaf osmotic potential (), leaf turgor potential (_P), leaf transpiration, and leaf diffusive resistance were determined on combinations of the water and N stress treatments. Although high-N plants attained similar or slightly lower _L than low N plants as a result of the water stress, high-N plants maintainedlower stomatal resistances at the lower _L. High-N plants also extracted more water from depths below 0.3 m in the soil profile compared with the low-N plants. Lower as _L declined resulted in higher _P in high-N plants, which was probably responsible for the lower stomatal resistances and higher rates of transpiration that were observed. Lower of the water-stressed, high-N plants could have resulted in the more efficient extraction of water from the soil profile. We conclude that the high-N plants were affected less by the water stress than low-N plants as evidenced by the maintenance of _Popen stomata, and higher rates of individual leaf transpiration despite similar reductions in _L during periods of low soil water availability.

Key Words: Zea mays L. • Osmotic potential • Stomatal resistance • Turgor potential • Transpiration • Water potential

² Associate professor of agronomy and professor of agricultural engineering, Univ. of Florida; professor of agricultural engineering, The Technion, Haifa, Israel; and professor of soil science, Univ. of Florida, Gainesville, FL 32611, respectively.

Received for publication February 18, 1985.

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