Phytotoxic lesions of chromium in maize D.C. Sharma a,b, * , C.P. Sharma a,b , R.D. Tripathi a,b a Department of Botany, Lucknow University, Lucknow-226007, India b Ecotoxicology and Bioremediation Group, National Botanical Research Institute, Rana Pratap Marg, Lucknow-226001, India Received 25 July 2001; accepted 23 November 2001 Abstract Chromium (Cr) is fairly abundant in the earthÕs crust and ranks fourth among the 29 elements of biological im- portance. Besides natural sources, Cr enters biotic components of the ecosystem in various ways. Of other major in- dustrial 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. Ó 2003 Published by Elsevier Science Ltd. Keywords: Chromium; Metabolism; Maize; Phytotoxic lesions 1. Introduction Chromium is an essential trace element for human beings and animals (Mertz, 1969; Schwarz, 1972). Whether chromium has any role in plant metabolism is still ambiguous. Of the borderline elements (Nieboer and Richardson, 1980), Cr is one of the most significant pollutants dis- charged by the tanning and plating industries. These effluents have been inadvertently used by farmers for irrigation. Both inhibitory (Soane and Saunder, 1959; Hara et al., 1976) and stimulatory (Warrington, 1946; Haas and Brusca, 1961) effects of Cr on plant growth have been reported. Cr caused foliar symptoms of in- terveinal iron chlorosis in oat (Hunter and Vergnano, 1953) and bush beans (Barcelo et al., 1985). Due to high oxidation power of chromium (Cr(VI)), membrane da- mage has been observed in bush beans. Chlorosis in upper plant parts has been considered due to toxic ef- fects in roots and the central parts of stems (Vazquez et al., 1987). Indirect effects are mainly caused by al- terations in the content of essential trace elements, de- crease in photosynthesis due to stomatal closure and alterations in the chloroplaste. During chlorosis in Nymphaea alba, decreased activity of d-aminolevulinic acid dehydratase activity due to Cr(VI) was observed by Vajpayee et al. (2000). Chemosphere 51 (2003) 63–68 www.elsevier.com/locate/chemosphere * Corresponding author. Address: Department of Botany, Lucknow University, Lucknow-226007, India. Tel.: +91-522- 471741; fax: +91-522-219558. E-mail address: dcsharma1@indiatimes.com (D.C. Sharma). 0045-6535/03/$ - see front matter Ó 2003 Published by Elsevier Science Ltd. PII:S0045-6535(01)00325-3