Regulation of Phosphate Influx in Winter Wheat: Root-Shoot Phosphorus Interactions

Abstract

Summary Plants of winter wheat (Triticum aestivum L. cv. Starke II) were grown at various external phosphate (Pi) levels for 10 days in order to investigate the effects of P nutritional status of roots and shoots on Pi influx and efflux measured at intervals the following 7 days. When external Pi was supplied to plants previously deprived of phosphate, P accumulated in the shoots to levels around four times that of controls due to high influx rates and proportionally large P-transport to the shoot. Efflux was, however, comparatively low. Split-root experiments with plants where one or two of the three seminal roots were pretreated with Pi for a period of up to 5 h showed increased phosphate influx in the non-treated root(s) when transferred to 32P-labelled Pi solution. Pretreatment with elevated light intensity for 5 h prior to split-root uptake experiments resulted in higher Pi influx in the part of the root system formerly exposed to Pi. The findings indicate that the shoot P concentration exerted a great effect in regulating the phosphate influx. The mechanisms involved are discussed.