Phytotoxic lesions of chromium in maize.

Chromium (Cr) is fairly abundant in the earth's crust and ranks fourth among the 29 elements of biological importance. Besides natural sources, Cr enters biotic components of the ecosystem in various ways. Of other major industrial sources, tanning and chrome-plating industries are prominent sources. Cr(VI) form of chromium is highly reactive and influences both plants and animals. Due to Mn present in soil, Cr(III) is oxidized to Cr(VI) which remains in soil for a long time and can affect plant growth and development. Since maize is an important food and fodder plant for human beings and cattle, a study was conducted to investigate the effects of Cr on some metabolic activities of maize (Zea mays L. cv. Ganga 5). Chromium caused visible lesions of interveinal chlorosis. Young leaves showed vein clearing. Also, a papery appearance was observed in leaves. Margins of leaves were curled and the leaves appeared pale at greater Cr exposure. Concentrations of both chlorophyll a and b were reduced by exposure to Cr, the activities of ribonuclease and phenyl phosphatase were greater while the activity of iron-porphyrin enzyme catalase was less and the activity of amylase was also much less in plants exposed to Cr. Chromium also caused retardation of soluble protein. Accumulation of Cr in roots was much at all the levels of chromium supply. Exposure to Cr resulted in reduction in grain production and quality.