Effects Of Exogenous Spermidine On Growth Of Tea Plant Under Lead Stress

In recent years with the development of industry and transportation, the heavy metallead which is widely exists in air, water and soil, seriously affected the human health.Lead could enter the plant through the roots or leaves and accumulate a lot, resulted theimbalance of the active oxygen metabolism in plant and inhibited the plant growth anddevelopment. Tea plant is one of the important economic species of tree in China, easilyabsorbed and accumulated lead ions. The issues of excessive lead content in tea seriouslyaffected the tea production, consumption and export in our country, therefore, thein-depth study of lead contamination of tea plant is critical. At present, the researchabout lead contamination issues of tea is mainly divided into the exploration about thepathway of lead contamination, the effects of the growth of tea under lead stress and thecharacteristics of lead ions absorption and accumulation in tea plant, but the researchabout prevention and control of the lead contamination is rare.Polyamines is a kind of natural antioxidants which is widely distributed in plants,common with spermidine, spermine and putrescine, Capable of regulating the plantgrowth and development, improving the plant resistance to the stress, and delaying plantsenescence. Existing studies have shown that, exogenous Spd can alleviate the heavymetal toxicity of plants, improve the resistance of plants to heavy metal stress. Andwhether exogenous Spd could increase the resistance of tea plant under lead stress hasnot been reported, so this study adopts the tea plant seedlings as the test materials,setting the heavy metal lead as stress factor, using the potted plant controlled method,throuth the research on the effect of exogenous Spd for tea plant growth under lead stress,to verify whether the exogenous Spd can improve tea plant resistance under lead stress,so that to lay the foundation for preventing lead contamination in tea plant cultivation.The main results of the research are as follows:1. Under the lead stress conditions, when the mass fraction of lead in the matrix is100mg·kg-1, the increment of plant height and stem diameter, the whole plant dry weightand fresh weight, the activities of antioxidant enzyme system, the soluble protein contentand chlorophyll content have got a certain degree of rise, shows that duing to inducingeffect, and better than50mg·kg-1lead deal, the results illustrate that low levels of lead stress can effectively stimulate the growth of tea, however, with the increase of the massfraction of lead in the matrix, the increment of plant height and stem diameter, the wholeplant dry weight and fresh weight, the activities of antioxidant enzyme system, thesoluble protein content and chlorophyll content decreased significantly, the tea plantgrowth has been inhibited, and when the mass fraction of lead in the matrix is600mg·kg-1, there are3strains of tea plant drying to death due to stress.2. Under the normal matrix cultivation conditions, the exogenous Spd treatmentwith the concentration of0.2,0.5,1.0and1.5mmol·L-1has improved a certain degree ofthe activities of antioxidant enzyme system and the soluble protein content, reduced theleaves relative electrical conductivity and the content of the Superoxide anion, Hydrogenperoxide, MDA, Proline in leaves of tea plant seedlings, stimulated the growth of the teaplant, but the effect is not significant. And the concentration of2.0mmol·L-1Spdtreatment has no significant inhibition on the growth of tea plant. Under the the massfraction of lead in the matrix is300mg·kg-1stress conditions, six different concentrationsof exogenous Spd have increased the activities of antioxidant enzyme system and thesoluble protein content, reduced the leaves relative electrical conductivity and thecontent of the Superoxide anion, Hydrogen peroxide, MDA, Proline in leaves of tea plantseedlings, alleviated the injuries suffered by lead stress of tea plant seedling, improvedthe resistance to lead stress of tea seedlings, stimulated the growth of the tea plant. Andthe concentration of1.0mmol·L-1Spd treatment has best enhance for the ability ofresistance to lead stress of tea plant.3. Under the the mass fraction of lead in the matrix is300mg·kg-1stress conditions,the increment of plant height and stem diameter, the whole plant dry weight and freshweight, leaf relative water content, chlorophyll content, leaf photosynthesis, chlorophyllfluorescence and the content of substances contained in tea have got a certain degree ofreduction, inhibited the normal growth of tea plant seedlings. The concentration of1.0mmol·L-1exogenous Spd spraying treatment, not only improved the increment of plantheight and stem diameter, the whole plant dry weight and fresh weight, leaf relativewater content, chlorophyll content, leaf photosynthesis, chlorophyll fluorescence and thecontent of substances contained in tea, but also effectively alleviated the inhibitoryeffect of lead stress on the growth of tea plant, ensure that the normal growth of tea plantseedlings under adversity.In summary, low concentrations of lead stress can stimulate the growth of tea plant,with the rise of the mass fraction of lead in the matrix, the growth of tea plant wassignificantly inhibited. Using the concentration of1.0mmol·L-1exogenous Spd foliar spraying of the tea plant, can effectively alleviated the suffered damage of the tea plant,enhance the ability of resistance to lead stress of tea plant, stimulated the normal growthof tea plant in adversity.