| Quercus acutissima Carr. is a deciduous tree which belongs to Fagaceae, and it is the important woody energy plants in China. It shows many valuable characteristics,including drought-resistant, anti-pollution, leanness-resistant, and so on. In a word, it has broad prospects for development and utilization. In this study, using soil irrigation and foliar-spraying with different concentrations of Cd2+and Pb2+combined pollution under field condition to research the effects on physiology and biochemistry of Q.acutissima seedlings and the absorption, accumulation, as well as transference properties of Cd2+and Pb2+in Q.acutissima seedlings. Preliminary explore the capacity of resistance and repair of Q.acutissima for the combined pollution of heavy metals in the soil. The results are as follows1.Under the condition of Cd2+and Pb2+combined pollution by soil irrigation, the net growth of seedling height, net growth of ground diameter, root length, root diameter, biomass decreased with the increasing concentration, especially in the high-concentration (50mg/L Cd2++2000mg/L Pb2+), the decrease is very significant. The net growth of seedling height of annual seedlings in Chongqing Wulong provenance was declined biggest, decreased by60.17%in the90th day under50mg/L Cd2++2000mg/L Pb2+concentration. With the concentrations increased, foliar-spraying of Cd2+and Pb2+combined pollution also caused net growth of seedling height, biomass decreased. Under the high-concentration (50mg/L Cd2++2000mg/L Pb2+), they were reached the minimum. Compared with the control group, the difference was very significant. The net growth of ground diameter, root length, root diameter did not change significantly. The net growth of seedling height of annual seedlings in Chongqing Wulong provenance was inhibited biggest which decreased by77.37%in the30th day under50mg/L Cd2++2000mg/L Pb2+concentration. There is different influence of Cd2+and Pb2+combined pollution,which were related with provenances and ages.2. Under the soil irrigation of Cd2+and Pb2+combined pollution, with the increase of stressing time, the contents of soluble sugar showed increased at first and then decreased, or increased at first and then decreased and increased again, the contents of MDA showed increased, or increased at first and then decreased, the contents of proline and the activity of SOD show up increased at first and then decreased in Q.acutissima seedlings leaves. But the result of foliar-spraying of Cd2+and Pb2+combined pollution was the contents of soluble sugar, MDA, proline and the activity of SOD in seedlings leaves were all showed up increased at first and then decreased. The physiological indicators of Q.acutissima seedlings in different provenances and different ages had different performance.3. The photosynthetic characteristics of Q.acutissima seedlings were influenced severely by soil irrigation and foliar-spraying of Cd+and Pb2+combined pollution. In high concentration (50mg/LCd2++2000mg/LPb2+), the net photosynthetic rate, stomata conductance and transpiration rate of Q.acutissima seedlings decreased significantly, while the intercellular CO2concentration increased gradually. Under the different treatments, the photosynthetic characteristics of Q.acutissima seedlings in different provenances and different ages had different influence by Cd2+and Pb2+combined pollution.4.1n both soil irrigation and foliar-spraying of Cd2+and Pb2+combined pollution, the physiological tolerance of annual Q.acutissima seedlings in three provenances to Cd2+and Pb2+combined pollution showed:Chongqing Wushan provenance> Henan Lingbao provenance> Chongqing Wulong provenance, and in different ages of seedlings showed:biennial seedlings>annual seedlings.5.In the soil irrigation of Cd2+and Pb2+combined pollution, the accumulation of Cd2+and Pb2+in vegetative organs of Q.acutissima seedlings would increased as the increase of the contents of Cd2+and Pb2+in soil, both were in the order of root> stem> leaf. At the concentrations of50mg/LCd2++2000mg/LPb2+, the contents of Cd2+in annual seedlings’ root reached the maximum14.825mg/kg(Chongqing Wulong provenance), while the contents of Pb2+reached the maximum378.490mg/kg(Henan Lingbao provenance). The maximum contents of Cd2+and Pb2+in biennial seedlings’root were less than annual seedlings’. In the foliar-spraying of Cd2+and Pb2+combined pollution, Cd2+and Pb2+mainly accumulated in the leaves of Q.acutissima seedlings. The contents of Cd2+reached the maximum1.715mg/kg(Chongqing Wulong provenance) in leaf of annual Q.acutissima seedlings at the concentrations of50mg/LCd2++2000mg/LPb2+, while the contents of Pb2+reached the maximum267.710mg/kg(Chongqing Wushan provenance). The maximum contents of Cd2+in biennial seedlings’ leaf were more than annual seedlings’, while the maximum contents of Pb2+in biennial seedlings’ leaf were less than annual seedlings’. There was interaction between Cd2+and Pb2+in combined pollution. Under the soil irrigation of Cd2+and Pb2+combined pollution, Pb2+promoted Cd2+to accumulate in each organ of Q.acutissima seedlings, while Cd2+ promote Pb2+to accumulate in seedlings’root, and inhibited Pb2+to accumulate in stem and leaf. In the foliar-spraying of Cd2+and Pb2+combined pollution, Pb2+promoted stem and leaf to accumulate more Cd2+, and Cd2+inhibitted stem and leaf to accumulate Pb2+. There’s had no significant impact of the absorption of Cd2+and Pb2+in root.6. In the soil irrigation of Cd2+and Pb2+combined pollution, the absorption and transfer of Cd2+and Pb2+were different in Q.acutissima seedlings at different provenances and different ages. The accumulation capacity of Cd the aboveground part of annual seedlings were in order of Q.fabri seedlings> Q.acutissima seedlings of Henan Lingbao provenance> Q.acutissima seedlings of Chongqing Wulong provenance> Q.acutissima seedlings of Chongqing Wushan provenance, while the transfer capacity of Cd were in order of Q.fabri seedlings> Q.acutissima seedlings of Henan Lingbao provenance> Q.acutissima seedlings of Chongqing Wushan provenance> Q.acutissima seedlings of Chongqing Wulong provenance. Both the accumulation and transfer capacity of Cd and Pb in the aboveground part of annual seedlings were in order of Q.acutissima seedlings of Chongqing Wushan provenance> Q.acutissima seedlings of Chongqing Wulong provenance> Q.fabri seedlings> Q.acutissima seedlings of Henan Lingbao provenance.Both the accumulation and transfer capacity of Cd were stronger than Pb in the aboveground part of Q.acutissima seedlings. The accumulation and transfer capacity of Cd in annual seedlings were stronger than biennial seedlings, while the accumulation and transfer capacity of Pb were less than biennial seedlings.According to the research on the Cd2+and Pb2+combined pollution tolerance for Q.acutissima seedlings, it showed that Q.acutissima seedlings had strong adaptability to the Cd2+and Pb2+combined pollution. The contents of Cd2+and Pb2+in the aboveground part of Q.acutissima seedlings didn’t reach the critical mass of hyper-accumulators (>100ug/g,>10000ug/g), but the maximum bioaccumulation factor and transfer coefficient were more than1, so it has ultra-enrichment potential of Cd2+in soil.Q.acutissima and other woody plants are not only tolerant to drought and barrenness, but also had long life and wide adaptability to soil. The study revealed that Q.acutissima seedlings had strong accumulation and transfer capacity of heavy metals (Cd, Pb) in soil, and the seedlings have clean-up and repaired effects on soil heavy metal pollution in a certain extent. And also revealed that Q.acutissima was not only a valuable woody energy plants, might also played a clean-up and repaired action in the pollution of soil with heavy metals. |
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