Improved potassium nutrition retrieves phosphorus-induced decrease in zinc uptake and grain zinc concentration of wheat.

Abstract

The negative effect of soil-applied phosphorus (P) on zinc (Zn) uptake by plants and its concentration in food grains could be a possible reason for low dietary intake of Zn. Likewise, owing to its critical role in plant tolerance to other abiotic stresses, potassium (K) was thought to retrieve P-induced decrease in grain Zn concentration of wheat. To test the above hypothesis, the effect of K application (50 mg kg-1 soil) on Zn concentration in shoot/grains and its shoot-to-grain translocation was studied in wheat (Triticum aestivum L. cv. Galaxy-2013) under low and optimal supply of both P (10 and 50 mg kg-1 ) and Zn (0 and 5 mg kg-1 ). The response of growth parameters and grain yield to optimal Zn, P and K applications indicated that all nutrients were limiting plant growth at low levels. Irrespective of P level, Zn application at optimal rate increased Zn concentration and uptake by straw and grains of wheat. Contrarily, optimal P application decreased Zn concentration but increased Zn uptake by wheat straw. More specifically, combined application of Zn and P at optimal levels decreased Zn concentration in grains from 43 to 32 mg kg-1 compared with optimal Zn application alone. Potassium application to optimal P- and Zn-supplied plants increased remobilization of pre-anthesis straw Zn store to grains by 50% and decreased Zn concentration in straw. Consequently, K application along with optimal Zn and P supply to plants completely retrieved P-induced loss in grain Zn concentration and also increased grain Zn uptake from 891 to 1249 µg per pot without significantly affecting grain yield. The K-induced increase in grain Zn concentration is attributed to K-driven higher post-anthesis Zn uptake and remobilization of pre-anthesis straw Zn store to grains. © 2018 Society of Chemical Industry.