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Magnesium Nutrition and Grain Yield of Maize Having Low Water Potential¹

Drought decreases plant production but the nutritional status of the plants may alter their susceptibility. Because Mg is a regulatory ion for several aspects of chloroplast photosynthesis, the effect of Mg nutrition on the grain yield of maize (Zea mays L. cv. Dekalb XL43) subjected to a water deficit was examined during most of the grain-filling period. Plants were grown at two soil Mg levels in a controlled environment capable of providing yields comparable to those in the field. The grain yield, shoot and root dry weight, leaf water potential (_w), and tissue mineral composition were determined. Immediately after tasseling, water was withheld from the soil of half the plants until the _w had decreased to –1.8 to –2.0 MPa, where it remained until maturity. Low water potentials resulted in a 50% reduction in grain yield and an accelerated leaf senescence. Despite small but significant differences in Mg concentration in roots, stems, and leaves, no differences attributable to differences in Mg nutrition were found in rate of plant dehydration, dry matter accumulation, or grain yield. It is concluded that differences in Mg content of the plant either 1) do not influence response to low – or 2) must be larger than we achieved to see an effect.

Key Words: Zea mays L. • Dry weight • Leaf senescence

² Assistant professor, Dep. Fisiologia Vegetal, Universidad de Navarra, Pamplona, Spain and plant physiologist, USDA/ARS, Dep. of Botany and Dep. of Agronomy, 289 Mom11 Hall, Univ. of Illinois, 505 S. Goodwin Avenue, Urbana, IL 61801.

Received for publication December 27, 1982.