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Although phosphorus (P) is known to reduce zinc (Zn) uptake by roots and root-to-shoot translocation, how this interaction is affected by changes in root morphology and arbuscular mycorrhizae (AM) are poorly understood. The current study determined the effects of P application rate (0, 25, 50, 100, 200, and 400 kg P ha −1 ) on Zn uptake by roots and root-to-shoot translocation in a high-yielding winter wheat system on calcareous soil. Root dry weight (RDW), root length density (RLD), and root surface area (RSA) significantly increased as P application increased from 0 to 50 kg ha −1 but were unaffected by rates >50 kg ha −1 . Zn accumulation (mg m −2 or μg m −2 ) by roots at flowering increased with application of 25 and 50 kg P ha −1 but slightly decreased with application of 100–400 kg P ha −1 . Zn accumulation in roots and in shoots at flowering and grain yield at maturity were positively correlated with RDW, RLD, and RSA. Root Zn accumulation was increasing with increased AM colonization from low AM (<10%) to 30% AM colonization. Whereas, continuously increasing AM colonization induced root Zn accumulation decrease, which may be mainly due to the decrease of root dry weight affected by P deficiency. P application rate did not significantly affect the ratio of Zn concentrations in roots vs. shoots or the ratio of Zn accumulation in roots vs. total Zn accumulation in the plant, indicating that Zn translocation from roots to shoots is not the primary factor limiting Zn concentrations in grain. These results indicate 1) that P application affects the Zn accumulation of wheat by affecting Zn uptake by roots and 2) that the changes in Zn uptake by roots and Zn accumulation following P application reflect changes in root morphology and AM colonization of roots. [ABSTRACT FROM AUTHOR]

Although the interaction between phosphorus (P) and zinc (Zn) in crop production has long been a focus of plant nutrition research, the effects of P on the Zn content of cereal crops remains unclear, especially in intensive agricultural systems with high rates of P application and low levels of available Zn. The current study of a high-yielding winter wheat system on the North China Plain compared the effects of P application (0, 25, 50, 100, 200, and 400 kg ha −1 ) on yield, biomass accumulation, Zn accumulation, Zn uptake during all crop stages, and Zn remobilization. In two growing seasons (2011–2012 and 2012–2013), the results indicated that P application significantly increased wheat grain yield and shoot biomass. Phosphorus application also significantly increased the P concentration and decreased the Zn concentration in shoots. Phosphorus application increased P accumulation (kg ha −1 ) throughout the growing season but the effect of P application on Zn accumulation (g ha −1 ) depended on crop stage. Zn accumulation increased with increasing P application rates at the jointing stage. Zn accumulation at the flowering and maturity stage increased with application of 25 and 50 kg P ha −1 but decreased with application of 100–400 kg P ha −1 in both cropping seasons. The Zn harvest index and the ratio of pre-anthesis to post-anthesis Zn accumulation were not greatly affected by P application rate. Zn remobilization into grain increased with application of 0–50 kg P ha −1 but then decreased with the further application of 50–400 kg P ha −1 in both cropping seasons. Overall, the effects of P application on Zn nutrition depended on P rate and crop stage. Lower P application rates (<50 kg ha −1 ) increased Zn accumulation especially after the flowering stage and increased Zn remobilization to grain. High rates of P (>50 kg ha −1 ), in contrast, significantly decreased Zn accumulation and remobilization in this high-yielding winter wheat system. The results indicate that optimal P management in intensive agricultural systems is needed to ensure both high wheat yields and high levels of Zn in grain required for human nutrition. [ABSTRACT FROM AUTHOR]