Study On The Effect Of Growth, Absorption And Accumulation Of Lead And Chromium In Tea Plants

With Fuding dabai tea and other varieties as materials, this study examined the characteristics of Pb and Cr press, the growth, accumulation and distribution of tea plant by hydroponics and pot experiment. The results showed as follows:1. The effects of growth of tea plant under Pb stress: The germination and growth of new tip of tea plant by hydroponics were restrained when the Pb concentration was 120mg·L^-1, and the damage symptoms were visible even to death. The Pb-tolerationg ability of different varieties were difference, the order was: Mingshan 131> Fuding dabai > Mingshan 213. The diagnosis of Pb pollution could be got from the toxicological map. When the Pb concentration≥240 mg·L^-1, there were significant negative impact on the content of chlorophyll, photosyntheti -c rate, stomatal conductance and transpiration rate of tea plant. The damaged symptoms of the potted planting tea plant was not visible when the Pb was added into the soil at the concentration of 25-250 mg·kg^-1. The growth(stem diameter at base, firsr branch diameter, height, fall twig length, length of l-shoot-2-bud)and the photosynthesis indexes(content of chlorophyll, photosynthetic rate, stomatal conductance and transpiration rate) were higher than CK when the concentration below 150 or 200 mg·kg^-1. It showed that the growth and photosynthesis could be promoted at thses concentration level. But when the concentration was higher than 200 mg·kg^-1,the growth and photosynthesis were restrained obviously. The activity of SOD, CAT and POD exhibited an up-down trend with the concentration, and the highest points were at the Pb concentration about 300 mg·kg^-1.2. The absorption and accumulation property of Pb in tea plant: The results of hydroponics and pot experiment showed that, the Pb content of organ rose with the Pb concentration ,and was markedly positive to the added concentration. Pb has a low anctivity in tea plant, and most of the Pb was fixed in fine root, and transferred to upground parts hardly . The order of the Pb content was: fine root > coarse root > stem > shoot > old leaf > new tip. On the conditions of this study, the Pb content of coarse root of tea plant by hydroponic reached 20.81-87.50 mg·kg^-1, fine root was 60.93-165.67 mg·kg^-1, stem was 0.98-14.03 mg·kg^-1. It showed that the roots and stem had the ability of ultra-accumulation of Pb, but the mechanism of physiological and biochemical and wether we can use this characteristics of tea plant to decontamination of Pb will be study in the future. The order of the Pb content in tea plant by pot was fine root > coarse root > stem > new tip > old leaf > shoot. On the conditions of this study, when the added Pb concentration was 150mg·kg^-1, and the concentration of soil was 159.31 mg·kg^-1, the Pb content of new tip (one bud and two leaves) was higher than the National Standards(≤5mg·kg^-1).3. The effects of growth of tea plant under Cr stress: When the Cr concentration was 20-100mg·L^-1, there were significant negative impact on the germination and growth of new tip of tea plant by hydroponics, and the damage symptoms were visible; The Cr-tolerationg ability of different varieties were difference. The content of chlorophyll and photosynthesis of the tea plant were restrained under Cr press. When the added Cr concentration was below 50mg·kg^-1, the growth of tea plant by pot was promoted, and above 75 mg·kg^-1, the growth of tea plant by pot was restrained; and above 100mg·kg^-1, the photosynthesis were also restrained. The activity of SOD tortuously dropped with the Cr concentration, but higher than CK all(except the concentration of 250 mg·kg^-1). The activity of CAT and POD exhibited an up-down trend with the concentration, and the highest points were at the Cr concentration about 150 mg·kg^-1.4. The absorption and accumulation property of Cr in tea plant: The Cr content of organ rose with the Cr concentration ,and was markedly positive to the added concentration. The results of hydroponics showed that, the order of the Cr content in tea plant was: fine root > coarse root > stem > shoot > old leaf > new tip. There were some differences among the absorption, accumulation and migration ability of Cr in tea plant. The fine root of Fuding had a larger ability of accumulation of Cr and lower proportion to transfferred to upground parts than other varieties. The results of pot experiment showed that, the order of the Cr content in tea plant was fine root > coarse root> old leaf > sten>branch≈new tip. On the conditions of this study, when the added Cr concentration was 250mg·kg^-1, and the concentration of soil was 314.88mg·kg^-1, the Cr content of new tip (one bud and two leaves) was5.54 mg·kg-1,which was higher than the standard of NY 693-2003. So, wether the existing standard obout the limitied of Cr in soil(150 mg·kg^-1) was scientific and rational need to study in the future.