Effect of Zinc Deficiency on the Accumulation of Boron and Other Mineral Nutrients in Barley

Abstract

AbstractThe hypothesis that Zn deficiency enhances the accumulation of B in barley (Hordeum vulgare L.) was tested in plants grown in nutrient solutions containing varying concentrations of B. Mean daily B uptake rates in 3‐week‐old seedlings supplied no Zn (−Zn treatment) were from 2 to 2.5 times higher as in plants supplied 2 µM Zn (+ Zn treatment). These effects were observed after only 7 d growth without added Zn. During this time, Zn in grain reserves and contaminant‐Zn were still adequate to maintain all plants with an internal tissue Zn concentration well above the critical tissue concentration (about 15 mg kg−1 Zn on a dry weight basis), and no yield response to Zn supplementation occurred. The effects of Zn on B uptake, therefore, support the concept that Zn performs a protective role at the external surfaces of, or in, root‐cell membranes. When the concentration of B in the nutrient solution was extremely high (e.g., 3000 µM), this protective effect of Zn disappeared and plants in all treatments developed B toxicity symptoms and accumulated high B concentrations. Other nutrients were also accumulated under Zn deprivation—namely, P, NO3, S, Ca, Mg, K, and Cu, but not Fe. Higher concentrations of P in the nutrient solution resulted in higher uptake rates of all ions, especially in the ‐Zn plants. A similar but smaller effect of added P on ion uptake occurred in +Zn plants.