Toxic effect and threshold of lead (Pb)on three tobacco cultivars (i.e.,Cuibi-1 ,K-3 2 6 and Yunyan-87)were studied using a pot experiment with varying Pb additions.In general,the toxicity induced reductions on theheight,leaf size and root length of the tobacco plants.However,the tobacco's sensitivity to Pb varied from cultivarsto cultivars.In addition,the plants were most sensitive to the toxicity during the middle growth period,on thestems and the lower leaves.For instance,the EC1 0 (i.e.,the available soil Pb content causing 1 0% reduction intobacco mass)of different parts of Cuibi-1 decreased in the order of:lower leaves 展开▼
