烟草对土壤铅的吸收、转运及分配特征

采用室外盆栽试验方法，开展烟草不同生育期铅吸收转运及分配特征的研究。结果表明：土壤铅处理对烟草生长有较明显的抑制作用，且生育前期比生育后期更明显；烟草根系对铅的阻滞作用较强，以限制铅由根系向地上部运输。烟草各生育期根、茎和叶中铅含量均随土壤铅浓度的增加而升高，其中根部的上升幅度最大，随着生育期的推进，烟草各器官铅含量从团棵期至现蕾期呈现先降低后升高的趋势，根部铅含量从现蕾期至成熟期呈现下降趋势。土壤添加外源铅后，烟草生育期内茎和叶的铅转运系数分别介于0．35—1．00和0．25～0．91之间，茎和叶的转运系数随着铅浓度的增加和生育期的推进呈下降趋势。烟草各器官中铅含量介于13．8～180．74mg·kg^-1之间，各器官铅含量的分布规律为根〉茎〉叶，各器官铅积累量总体为叶〉根〉茎，但成熟期在T2和T3处理下表现为根〉叶〉茎。在土壤铅浓度较低时，烟草体内铅较易向地上部分转运，旺长期至现蕾期阶段是烟草体内铅向地上部分转运的关键时期。

Uptake, Transfer and Distribution of Lead in Tobacco

Elevated lead （Pb） in tobacco profoundly impacts the quality of cigarettes. Uptake and transfer of Pb by tobacco are dependent on its growth. A pot experiment was performed to examine Pb uptake, transfer and distribution in tobacco grown in soils spiked with different Pb levels during the whole growth period. Lead additions obviously inhibited tobacco growth, especially at early stages. Tobacco roots had strong retention of Pb, which restricted transportation of Pb from roots to shoots. Concentrations of Pb in different organs ranged from 13.89 mg· kg-1 to 180.74 mg·kg-1,with an order of roots〉stems〉leaves, increasing with Pb additions during growth periods. As the growth progressed, con- centrations of Pb in tobacco roots, stems and leaves showed a rising-and-falling trend from the rosette stage to squaring stage. The root Pb decreased from the squaring stage to mature stage. Transfer coefficients of Pb from roots to leaves and stems ranged from 0.35 to 1.00, and 0.25 to 0.91, respectively, both decreasing with growth stages and Pb additions. Lead accumulation was generally in order：leaves〉roots〉 stems, whereas roots〉leaves〉stems at mature stage in T2 and T3 treatments. Peak and squaring stages were the critical periods for Pb trans- fer from tobacco roots to shoots.