Lead Toxicity on Three Varieties of Tobaccos

Toxic effect and threshold of lead (Pb) on three tobacco cultivars (i.e., Cuibi-1, K-326 and Yunyan-87) were studied using apot experiment with varying Pb additions.In general, the toxicity induced reductions on the height, leaf size and root length of the tobacco plants.However, the tobacco's sensitivity to Pb varied from cultivars to cultivars.In addition, the plants were most sensitive to the toxicity during the middle growth period, on the stems and the lower leaves.For instance, the EC10 (i.e., the available soil Pb content causing 10% reduction in tobacco mass) of different parts of Cuibi-1decreased in the order of:lower leaves<root<stem<middle leaves<upper leaves.For K-326, the order was:root<upper leaves<stem<lower leaves< middle leaves;and, for Yunyan-87, it was:upper leaves<lower leaves<stem<middle leaves.Since Cuibi-1was most sensitive to Pb of the three varieties, the EC10 for the middle leaves of Cuibi-1, 66.88 mg·kg-1, was suggested to be set as the Pb toxicity threshold for the three varieties, and for the tobacco-producing soils in Fujian in general as well.