Organic acids differ in enhancing phosphorus uptake by Triticum aestivum L.—effects of rhizosphere concentration and counterion

摘要

Organic acids such as citrate and oxalate have been implicated in enhancing many rhizosphere processes including nutrient acquisition. This study was conducted to determine the importance of organic acid type and concentration on rhizosphere P mobilization and subsequent uptake by wheat (Triticum aestivum L.) roots and its translocation to shoots. A single wheat plant was grown in soil-filled rhizosphere microcosms and allowed to pass through a KH₂PO₄ 33P-isotopically labeled patch of calcareous soil. Two days after 33P-injection, citrate and oxalate at concentrations of 1 mM and 10 mM were injected into the microcosms at the same patch every day over a period of 4 days. Oxalate resulted in a several-fold enhancement in plant 33P accumulation, while citrate had no such effect. In comparison with oxalate, high rates of citrate mineralization were observed suggesting that this reduced its potential to enhance plant 33P acquisition. This study concludes that organic acids cause an increase in P mobilization and P uptake by wheat but that this response is highly organic acid specific.