Effect Of Pb,Cd And Their Compound Pollution On The Physiological And Ecological Characteristics Of The Tea

Two years old Mengshan tea 213 was chosed as the research subject,under potted plant experiment,soil applicating of different concentration levels of PbCH₃COO)₂.3H₂O and Cd(NO₃)₂.4H₂O was carried out to determine the effects of Pb,Cd and Pb-Cd compound pollution on the growth and physiological index in leaves of Mengshan tea, meanwhile,the absorption and accumulation of lead and cadmium in tea plant were discussed,it will provide the oretical reference for controlling the contents of heavy metal in the tea,discussing the characteristics of pollution,controlling the heavy metal pollution and improving the tea quality.The maim results are as below:(1) Effects of different lead concentrations on growth and physiological index in leaves of Mengshan teaWith the increasing concentrations of lead,the lead had a significant effect to the yield of summer tea,the coefficient of correlation was -0.937^**(P＜0.01),and the green deficiency symptoms were visible,the growth of tea was inhibitted.The chlorophy 11(Ch1) content of spring tea supplemented with Pb was higher than CK.The Ch1 content of summer tea was first stimulated and then inhibitted,when the lead concentration was 100 mg/kg,the Ch1 content reached the maximum2.92 mg/g and when the concentration was 1500 mg/kg,Ch1 content reached the minimum2.28 mg/g.With the increasing concentration of lead,the malondialdehyde(MDA) and free praline content in leaves were enhanced,and the summer tea's was higher than spring tea's; The soluble sugar of spring tea was first stimulated and then inhibitted,and the soluble sugar of spring tea and summer tea reached the maximum at the same time when the lead concentration was 200 mg/kg.(2) Effects of different cadmium concentrations on growth and physiological index in leaves of Mengshan teaLow concentration of cadmium(＜10mg/kg) has no obvious adverse effect on the tea plant,when the cadmium concentration reached 10mg/kg,some leaves becomed yellow, and when the cadmium concentration reached 60 mg/kg,the tea plant harmed to die;With increasing concentration of cadmium,the yield of spring and summer tea were decreased, and the coefficient of correlation was -0.867^*(P＜0.05),-0.878^**(P＜0.01).The chlorophyâ…¡(Châ… ) content of most spring tea supplemented with Cd was higher than CK and the increasing trend was raised firstly and inhibitted later;The chlorophyâ…¡content of summer tea was significantly decreased with increase of cadmium concentration, and the coefficient of correlation was -0.997^**(P＜0.01).The malondialdehyde(MDA) content in spring and summer tea was enhanced with the increase of cadmium concentration,the coefficient of correlation were 0.970^**, 0.994^**(P＜0.01)respectively,and the summer tea's was higher than spring tea's.The free proline of spring tea was enhanced with the increasing of Cd concentration,and the coefficient of correlation was 0.829^*(P＜0.05).The free proline in summer tea was significantly enhanced,and the coefficient of correlation was 0.980^**(P＜0.01),and the content of free praline in summer tea was higher than that in spring tea;The soluble sugar content in spring tea was higher than CK and the increasing trend raised firstly and then inhibitted,the coefficient of correlation was -0.342,the difference was not significant;The soluble sugar content of summer tea was significantly decreased and the coefficient of correlation was -0.909^*(P＜0.05)(3) Effects of different Pb-Cd compound pollution on growth and physiological index in leaves of Mengshan teaWith the increasing of concentration(Cd＞10mg/kg,Pb＞200mg/kg),the growth of tea was inhibited,and the the yield was decreased with the increase of compound concentrations.In spring tea,the Pb-Cd interaction inhibit-ted the synthesis of chlorophyll a,chlorophyll a+b and the soluble sugar,and promoted the synthesis of chlorophyll b,MDA and the free praline.Cd plaied a major role to the synthesis of free praline,and the Pb-Cd interaction plaied a major role to the synthesis of other physiological index.In summer tea,the Pb-Cd interaction promoted the synthesis of all the physiological index.,and the Pb-Cd interaction plaied a major role to the synthesis of chlorophyll a,chlorophyll b ana chlorophyll a+b,Cd plaied a major role to the synthesis of free praline and soluble sugar,the Pb plaied a major role to the synthesis of MDA.(4) The absorption and accumulation of lead and cadmium in Mengshan tea plantThe distribution of lead and cadmium in the tea could be sequenced as:absorbing roots＞stems＞mature leaves＞tea flush,the lead contents in the different parts(absorbing roots,stems,mature leaves,tea flush) of the tea plant were significantly enhanced with increasing concentration of lead,and the cadmium contents in the absorbing roots,stems,mature leaves were significantly enhanced with increasing concentration of cadmium.With compound pollution,cadmium had a synergism effect with the accumulation of lead in absorbing roots,stems,spring tea,summer tea and lead had a synergism effect with the accumulation of cadmium in absorbing roots and had an antagonistic effect in the other parts of the tea plant.