Bioaccumulation of Lead and the Effects of Lead on Catalase Activity, Glutathione Levels, and Chlorophyll Content in the Leaves of Wheat

Soil contamination with heavy metals can lead to losses in agricultural yield and affect human health as the metals enter the food chain, which has become a worldwide problem. Compared with other heavy metals, lead (Pb) contamination is high because of its long persistence in soil and highly toxic effects on crop production and human health. Wheat is the world's most widely grown cereal and can be cultivated in a wide range of soils. Recently, wheat has been grown widely in northern China. The aims of the present studies are to investigate the effect of Pb on antioxidative metabolisms and chlorophyll synthesis of wheat 'Jinan No. 17.' Moreover, calcium ion (Ca2+) levels and bioaccumulation of Pb in the leaves of wheat were investigated. The soil was artificially contaminated with different concentrations of Pb [0, 100, 500, and 2000 Pb mg kg(-1) dry weight (DW) soil as lead nitrate, Pb(NO3)(2)]. The catalase (CAT) activity and glutathion (GSH), chlorophyll a, chlorophyll b, and total chlorophyll contents in the leaves of wheat were analyzed with a spectrophotometer at different stages of wheat growth. Calcium levels and bioaccumulation of Pb in the leaves of wheat were studied with inductively coupled plasma sector field mass spectrometry (ICP-SF-MS). The results indicated that Pb stress can increase the content of GSH in leaves of wheat, thereby affecting the activity of CAT. Both low and high concentrations of Pb stimulated chlorophyll synthesis at early stages of wheat growth and inhibited chlorophyll synthesis at later stages of wheat growth. Furthermore, Ca and Pb in leaves of wheat increased with increasing concentrations of Pb on day 34 as determined with ICP-SF-MS.