Effects of Water Stress on Nitrogen Nutrition of Grain Sorghum

Abstract

A solution culture experiment was conducted to study the effects of solution osmotic potential and nitrogen (N) supply on growth and N content of grain sorghum cv. Texas 610SR. Polyethylene glycol-6000 was used to impose solution osmotic potentials of -0.1, -0.4, -0.8, and - 1.1 MPa during the fourth week of growth. Plants were harvested at 6 weeks. Dry matter yields, total plant N content and mean rate of N uptake per unit root weight were significantly decreased by decreases in solution osmotic potential and N supply. Numbers of leaves expanded after imposition of the solution osmotic potential treatments were also reduced significantly by decreasing solution osmotic potential and decreasing N supply. Decreasing solution osmotic potential decreased mean N concentrations in leaves, had no effect on mean N concentrations in roots, and increased N concentrations in stems plus immature leaves, and in whole tops. The form of relationships between leaf N concentration and yield prevented the calculation of critical N concentrations at any level of solution osmotic potential.