Effects Of Pb Stress On The Growth Of Poplar (Populus Deltoids×P.Nigra) Seedling And Its Pb Accumulation

Soil Pb pollution is a major ecological concern due to its impact on the security of the environment and the healthy of the human survival. The result of different Pb stress on the growth of the plant and its Pb accumulation characteristics could supply important scientific knowledge of the phytoremediation of the soil, but the available information has not been seen. In order to understand the growth of poplar(Populus deltoids×P. nigra) seedling and its Pb accumulation, transformation and distribution in the upper Yangtze River Basin, a controlled pot-experiment cultivated with one-year old poplar was arranged with different treatments of four Pb concentrations (CK:0mg-kg-1; T1:200mg’kg-1; T2:450mg-kg-1; T3:2000mg-kg-1) in field. Meanwhile, C, N and P accumulation, and N and P use efficiency under different Pb stresses in acid purple soil and alkaline purple soil were also characterized. The results showed that:Low Pb concentration had no significant effect on the height growth and diameter growth of the poplar grown in two different soils. However, the height growth of the poplar grown in acid purple soil decreased significantly under the treatment of T3. The root length of the poplar showed a decreased tendency with the increase of Pb supplies in both soils. The biomass of the poplar showed a decreased tendency with the increase of Pb supplies in both soils. Meanwhile, the total biomass was much higher in alkaline purple soil than that in acid purple soil under corresponding Pb treatment. Biomass distribution pattern under different Pb treatments in alkaline purple soil showed the same order as stems>coarse roots>leaves>fine roots. The ratio of root to stem had no significant difference under different treatment in acid purple soil and the ratio under the treatment of T3was the highest in alkaline purple soil.Low Pb concentration had no significant effect on the content of chlorophyll a and total chlorophyll contents, but the content of chlorophyll a, chlorophyll b and total chlorophyll contents decreased significantly compared with the control under the treatment of T2and T3. Compared with the poplar in acid purple soil, the poplar in alkaline purple soil had the higher LCP, AQE and Pmax but the lower Lsp. Meanwhile, the poplar in alkaline purple soil had the higher Rd, CE and Pmax but the lower Csp compared with the poplar in acid purple soil.Accumulations of C, N and P in plant showed a decreased tendency with the increase of Pb supplies in both acid purple soil and alkaline purple soil. Compared with the poplar in acid purple soil, the accumulations of C, N and P in alkaline purple soil were much higher. Distribution patterns of C, N and P in the poplar were altered in both soils when supplied with different Pb concentrations. C, N and P accumulation of the fine root significantly increased with the increase of Pb supplies in acid purple soil, but which of fallen leaves displayed the contrary tendency. In contrast, C, N and P accumulation of the fine root showed a decreased tendency with the increase of Pb supplies in alkaline purple soil, but which of fallen leaves increased. In addition, P use efficiency of the poplar in both soils showed an increased tendency with the increase of Pb supplies but the N use efficiency significantly decreased under the treatments of higher Pb supplies.Pb concentration and accumulation were significantly increased with the increase of Pb supplies under two soils. Compared with the poplar in acid purple soil, the poplar in alkaline purple soil had the higher Pb accumulation of coarse root but the lower of the fine root. With the increase of Pb supplies, the difference of the Pb accumulation of the stem in both soils increased gradually. In two different soil conditions, Pb accumulation of the coarse root showed an increased tencendy and Pb accumulation of the leaf showed a tencendy that increased first but decreased then with the increase of Pb supplies. BC, TF and TF’of the poplar in acid purple soil under the treatment of T3were much higher. Ti of the poplar in acid purple soil under all the treatments was also much higher.Cd concentration of the leaf was significantly increased under the treatment of T1and Cd concentration of the leaf in acid purple soil was significantly increased compared with the control. Cd concentration of the leaf was much higher in corresponding treatments in alkaline purple soil compared with the poplar in acid purple soil. Compared with the poplar in acid purple soil, the poplar in alkaline purple soil had the higher Zn accumulation. In two different soil conditions, Zn accumulation of the coarse root obviously lower than that of the stem and the leaf. Zn accumulation of the poplr decreased with the increase of Pb supplies and which was much higher grown in alkaline purple soil.The results from this study indicated that the growth and physiology characteristics of the poplar affected different under different Pb stress and soil types. Nutrient uptake by plants and its distribution patterns were significantly affected by the presence of Pb. The accumulation of Pb in poplar grown in acid purple soil was much higher. These results didn’t proclaim the mechanism of the growth and the accumulation characteristics of the poplar, but provided efficient scientific data for phytoremediation in Pb-contaminated environment in the upper Yangtze River Basin.