| This study examined the characteristics of Pb uptake, accumulation and distribution by tea plant (Camellia sinensis L.) with solution culture and pot experiment. Pb contents were analyzed in samples of absorptive root, radicella root, main root, mature stem, young leaf, mature leaf, young stem and tea shoot were taken from three newly bred varieties, i. e. Zhenongll3 Zhenongll3, and Longjing43, grown in trophic solution and pot trial. After spraying Pb on leaves, adding Pb to the solution and pot soil, a series of physiological index, Pb conformation in vivo, and shoot growth rate, and protective enzyme activities were also investigated. The results showed as follows:1. Pb can be taken up not only by leaves of tea plant and transported to the roots , but also by roots and transported to the upper parts . Pb uptaken can be distributed in all parts of tea plant. The behavior of accumulation and distribution of Pb in tea plant showed similar rules in this two different uptake ways. The concentration of Pb in underground parts was higher than that of aerial parts. The highest concentration was in absorptive roots and mature stems. Pb concentration in underground parts was sequenced as: absorptive roots > radicella roots > main roots. In upper parts, the sequence showed as: mature stems > young leaves > mature leaves > young stems) bud.2. Lead in tea plant is mainly in the form of oxalic acid lead .phosphoric acid hydrogen lead (PbHPO4) and phosphoric acid lead( Pb3(P04 )2) , and some acid hydrogen lead and so on . The contents of main Pb forms in the roots ,stems and leaves are 97. 34% , 98. 35% and 99.65% respectively of the total lead that presents in tea plant . In root, Pb is mainly distributed in cell wall and the cell nucleus . In stem, it is distributed in cell nucleus, and which in cytoplasm and in leaves it is located in cytoplasm and cell wall.In non Pb - treated soil, the sequence of Pb forms in soil is showed as : sulphide united lead >carbonate united lead>adsorbed lead >organic and residual united lead >exchangeable lead > water dissolved lead .After lead is added to soil, the Pb forms are sequenced as : sulphide united lead >exchangeable lead > carbonate united lead > organic and residual united lead >adsorbed lead> water dissolved lead. Sulphide united lead and exchangeable lead contents are higher as compared with other forms.3. The growth of tea plant under the effect of Pb was significantly different among the three varieties. In the concentrations of the experiment, Pb could hasten the growth of Zhenong113 and Longjing43, while the growth of Zhenongll7 was restrained when the concentration was 430rag/kg.4. The net photosynthetic rate also showed different results among the three varieties in the same concentration of Pb (160mg/kg). This Pb concentration restrained the growth of Zhenongll7 greatly and ZhenongllS slightly, while enhanced that of Longjing43. The Pb concentration of 430mg/kg decreased the growth of all the three varieties.The permeability of cell membrane changed after the Pb uptake by tea plant. The permeability of cell membrane in leaves increased lightly with Pb concentration increasing in Zhenongll3 and Longjing43. The permeability increased abruptly in Zhenongll7 when the Pb concentration is 430mg/kg (P < 0.01) and is 174.57% higher than control.The trend of MDA concentration in leaves was similar to the permeability of cell membrane except that in Longjing43.5. The protective enzyme activities in tea plant changed under the Pb treatment. The activity of POD increased in these three varieties .The POD activity in Zhenongll7 increased significantly (p<0. 01) . The POD activity in Zhenongll3 increased significantly (p<0. 05) under the concentration of 430mg/kg . The POD activity in Longjing43 increased significantly (p<0. 01) under the concentration of 160mg/kg , While it dropped significantly (p <0.01) under the concentration of 430mg/kg.In Pb concentration of 430mg/kg , the activities of SOD in ZhenongllS and Longjing43 increased significantly...
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