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Abstract
Seven‐day‐old wheat plants (Triticum aestivum L. cv. Gamenya) were grown for a further 11 and 29 days using a split root technique such that 2.5 μM Zn was added to both (Zn++), one (Zn+0), or neither (Zn00) of paired half‐root systems in an otherwise complete nutrient solution. When compared with Zn++ plants, the Zn+0 treatment had no effect on dry matter (DM) of wheat plants or plant parts. Indeed, in all respects, Zn+0 plants appeared identical to Zn++ plants. By contrast, at final harvest, Zn00 plants had symptoms of severe Zn deficiency and P toxicity, and depressed whole plant DM. The Zn+0 treatment was used to calculate translocation rates of Zn from one half‐root system to the other while all three treatments were used to study the effect of Zn supply on P accumulation. Zinc translocation from day 18 (D18) to D36 from the half‐root system supplied with Zn (Ra) to the half‐root system not supplied with Zn (Rb) was 1.0 to 1.5 mg Zn/kg DM RB/day. This rate of translocation could maintain a concentration of 9 to 14 mg Zn/kg DM in Rb if the growth rate of Rb remained unchanged. When compared with Zn++ plants, Zn+o plants had slightly depressed P concentration in some shoot parts due to a small depression in P absorption rate by the root not supplied with Zn. By contrast, at final harvest, Znoo plants had markedly enhanced P concentrations in shoots and shoot parts. Between the two harvests, Zn00 had depressed the absorption rate of P. That Zn+0 plants behaved like Zn++ plants suggests that the enhanced P concentration in Zn deficient (Zn00) plants was mediated primarily through an effect of Zn in the shoots rather than in the roots.
Notes
This work was supported by a Murdoch University Research Scholarship.
Present Address: Agronomy Department, Waite Agricultural Research Institute, Glen Osmond, 5064, South Australia, Australia.