Variation in calcium levels leads to changes in the copper metabolism in barley

Abstract

Barley (Hordeum vulgare L.) cv. Jyoti was grown in refined sand at three levels of Cu, namely, deficient (0.01 µM), normal (1 µM), and excess (100 µM), each at three levels of Ca, low (0.04 mM), adequate (4 mM), and high (8 mM). Low Cu levels resulted in a decrease of the dry weight of whole plant and in the leaf chlorophyll content as well as Cu and Fe concentrations and activity of polyphenol oxidase and in an increase of the activities of ribonuclease and peroxidase and concentration of reducing sugars. These effects were further accentuated by a combined deficiency in Cu and Ca. The synergy between Cu and Ca was manifested when a low Ca level aggravated the effects of excess Cu by further reducing the dry weight and concentration of chlorophyll, leaf Fe and increasing the sugar concentration and activities of polyphenol oxidase and ribonuclease. In barley the Cu toxicity effects such as reduced dry weight, increase of leaf Cu, Ca, and reducing sugar concentrations, and stimulation of the activity of polyphenol oxidase were further enhanced by excess Ca. At all three levels of Ca, the addition of a normal Cu level to low Cu plants alleviated the Cu deficiency effects except for α-amylase activity, after 48 h. The effects of Ca deficiency were partially alleviated upon the resumption of Ca supply to Ca deficient leaf discs. © 2001, Taylor & Francis Group, LLC.