| With recent developments in the economy, the effect of industrial and agricultural wastes on the soil environment has become more serious. There is a significant focus on the pollution of heavy metals. The heavy metal soil pollution in the city is so serious that it has major side effects on the urban ecological system. Loropetalum chinense var.rubrum belongs to Hamamelidaceae and has many desirable ecological characteristics. It produces an abundance of attractive pink flowers and colored leaves. It is also fast-growing to tolerate disease and harmful insects. Nowadays, it is widely used as potted landscape and gardening plant to beautify our environment. The test materials of this experiment were the three groups of Loropetalum chinense var.rubrum. The groups are named the Nenyehong group, the Touguhong group, and the Shuangmianhong group. Using the three groups of Loropetalum chinense var.rubrum as the test material, a pot experiment with soil was conducted to study the effects of Pb2+ stress and Cd2+ stress on photosynthetic characteristics(20d), the contents of pigments, and the physiological and biochemical characters in the leaves(30d) of Loropetalum chinense var.rubrum. Moreover, the effect of Pb2+ stress and Cd2+ stress on the character of growth and accumulation was studied (40d). The main conclusions were as follows:1.There was a significant decline in the value of Pn when the concentration of Pb2+ and Cd2+ increased, although, the value of Pn increased when the treatment of Pb2+ was 100mg-kg-1. Gs and Tr changed also following the same trend of Pn but within a smaller range. However, there was an increase in the concentration of CO2 when the concentration of Pb2+ and Cd2+ increased except in the Nenyehong group under the treatment of Pb2+. When the concentration of Pb2+ and Cd2+ increased, there was a decline in the value of WUE in the leaves of the Touguhong group and the Shuangmianhong group.2. The content of Chlorophyll a, Chlorophyll b, and the total Chlorophyll in leaves of Loropetalum chinense var.rubrum increased at first, and then decreased when the concentration of Pb2+ and Cd2+ were raised. However, the content of total Chlorophyll in the Tougguhong group significantly decreased with the treatment of Cd2+ at 200mg·kg-1; Chlorophyll b was not as sensitive as chlorophyll a. Chlorophyll a/b and the content of Carotenoid in leaves of the three groups declined under the treatment of Pb2+ and Cd2+.3. The content of anthocyanin in the leaves of the three groups increased at first and then decreased when the concentration of Pb2+ were raised. Under the treatment of Cd2+, the content of anthocyanin declined significantly when the treatment of Cd2+ was lOmg·kg-1 and 100mg·kg-1. Under the treatment of Pb2+ and Cd2+, the changes in the anthocyanin content and the activities of PAL were positively correlated. The content of soluble sugar increased at first, and then significantly decreased when the concentration of Pb2+ was raised, and increased at first, then slightly dropped when the concentration of Cd2+ was raised.4. From the appearance of Loropetalum chinense var.rubrum test plant, the leaves showed signs of deformation, discoloration, and necrosis spot symptoms under the stress of heavy metals. The tolerance concentrations of Loropetalum chinense var.rubrum of Pb2+ and Cd2+ were 1000mg·kg-1 and 200mg·kg-1.The Nenyehong group suffered more seriously than the other two test groups.5. Under the treatment of Pb2+(1000mg·kg-1) and Cd2+(200mg-kg-1). accumulation of Pb2+ and Cd2+ in the organs was tested as follows:Root> Stem> Leaf. The Pb accumulated mostly in the root system of the Loropetalum chinense var.rubrum. The concentrations of Pb2+ and Cd+ in the stem of the Nenyehong.the Touguhong and the Shuangmianhong group were 245.254,257.807,356.143 mg·kg-1 and 216.248,566.575,385.467 mg·kg-1, respectively, which accounted for 10.9%, 9.3%,11.4% and 33.1%,39.6%,37.3% of the total concentration. |
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