Phosphorus nutrition affects wheat response to water deficit

Plant leaf area affects both plant growth and yield. Although the effects of phosphorus and a ater availability on leaf area development have been studied as isolated factors, little work has been done on their possible interactions. A pot experiment was conducted to investigate the effects of both P and water availability on early leaf appearance and expansion in soft red winter wheat (Triticum aestivum L.), and to determine whether the effect of water deficit changes at each level of P nutrition and whether the soil water content affects plant P uptake, The soil mas a Lonewood loam (fine-loamy, siliceous, mesic Typic Hapludult), which had an available P level of 8.2 mg P kg(-1) (Mehlich III). Additional P was applied at 0, 10 and 20 mg P kg(-1) soil. Water treatments consisted of keeping soil-mater content at 80% (well metered) and 53% (stressed) of the 10 kPa soil-water content. Plant development, leaf appearance and expansion, and stomatal resistance were measured during the experiment. At harvest (38 d after emergence), leaf area, aboveground biomass, and P concentration were measured. Phosphorus and water availability exhibited a significant interaction on tiller and leaf appearance, which were reduced by water stress but only at 0 applied P, As individual factors, P and mater influenced different plant features. Lack of applied P decreased the rate of leaf appearance and, therefore, the final number of leaves and leaf area per plant. Water deficit reduced individual leaf area and, at 0 applied P, reduced rate of leaf appearance, number of simultaneously expanding leaves, and final number of leaves. Phosphorus uptake,vas increased only with added sail P, and not by water stress. The ability of plants to cope with mid water stress was enhanced by adequate P nutrition.