Physiological And Biochemical Changes In Response To Aluminum Treatment And Aluminum Accumulation In The Camellia Japonica

Acidic soil（p H<5.5）accounts for 50%of the world’s arable land area.The main harm of acidic soil to plants is active aluminum ions(Al³⁺).Aluminum ions inhibit the growth of the roots of most plants,thereby affecting plant yield and quality.Aluminum toxicity has become the main factor that harms the growth and development of plants on acid soil,so it has important theoretical and practical value for the study of the mechanism of aluminum tolerance of plants.Camellia is an evergreen shrub that grows on acid soil,and it can accumulate a certain amount of aluminum.In order to explore the physiological and biochemical response mechanism of camellia to aluminum and the accumulation effect of aluminum in the plant,the study uses camellia as the research material and uses plant physiology,biochemistry and other technologies to carry out Al³⁺research on camellia growth and development,nutrient absorption,antioxidant enzyme metabolism system,aluminum accumulation and distribution.The main results of the study are as follows:（1）Effects of aluminum on growth and nutrient absorption of camellia sinensis.The effects of aluminum on the growth and nutrient absorption of camellia chinensis were studied by hydroponic method,with biennial cuttings as the experimental material and aluminum（Al）treatment at 4 concentrations（0,0.5,1,2m M）.The results showed that the three aluminum treatments promoted the root growth of camellia sinensis to different degrees.Compared with the control group,0.5,1.0,and 2m M Al induced an increase in root biomass of 71%,118%,and 42%,respectively.The 1m M Al treatment was the most significant to promote the root growth of camellia sinensis.Compared with the control group,0.5m M and 1m M aluminum treatment significantly increased root activity,chlorophyll,photosynthetic rate,soluble sugar and soluble protein content,and decreased malondialdehyde and free proline concentrations.Studies on nutrient elements showed that compared with the control group,1m M Al significantly increased the concentration of N,P,Fe,Cu,Zn and Mn in the root system,while significantly reduced the content of Ca and Mg.The contents of aluminum in the mature leaves and roots of camellia japonica treated with 1m M aluminum were 7189mg/kg and 11192 mg/kg（dry weight）,respectively.（2）Effect of aluminum on antioxidant system of camellia sinensis.The effects of aluminum on antioxidant system of camellia sinensis were studied by hydroponic method,annual cuttings as experimental materials,and the Al treatment was at three concentrations（0,0.5,1m M）.The results showed that 0.5 and 1m M Al could significantly promote the growth of camellia sinensis roots.Compared with controls,aluminum processing under the root activity of hydrogen peroxide（H₂O₂）and superoxide anion（O₂^-）content is greatly reduced,root active oxygen dyeing in chengdu is low,and antioxidants in root and leaf（As A and GSH）content increased significantly,while aluminum processing under the antioxidant enzymes（SOD,POD,CAT,APX,GR,DHAR,MDHAR）activity significantly increased.These results indicate that the growth promotion of aluminum-induced camellia sinensis is related to the activation of antioxidant enzyme system.（3）Distribution of aluminum in the somatic cells of camellia sinensis.The distribution of aluminum in different organs and subcells of camellia sinensis was studied by using hydropture method and annual camellia sinensis as the experimental material.The results showed that there were significant differences in the content of aluminum in different camellia officinalis organs,and the concentration of aluminum was sequenced from high to low:new roots>old roots>leaves>xylem.The aluminum content of the new root was the highest,about 9.823g/kg（dry weight）,and the aluminum content in the xylem of the stem was the lowest,0.467g/kg.The aluminum content of leaves at different leaf ages was also different.The higher the leaf age,the higher the aluminum content.The aluminum content of the 5^th/6^th leaves was the highest,about 8.653g/kg.By measuring the aluminum content of different subcellular components of camellia leaves and roots,it was found that the aluminum content of the subcellular components of camellia treated with 1m M Al was ranked as cell wall>soluble component>organelles,of which the cell wall aluminum content accounted for 53.46%-76.42%.Fluorescent sections of camellia sinensis from different parts showed that aluminum was mainly accumulated in the cell walls of camellia sinensis roots and leaves.A study of Camellia leaves growing on acidic soil in different seasons found that during the growth period from April to September,the accumulation of aluminum in the leaves gradually increased.The aluminum content in the same parts of Camellia leaves collected in September was as high as 6.597g/kg（dry weight）.In addition,under field growth conditions,the order of aluminum content in different parts of Camellia in September was:new root>old root>leaf>branch phloem>flower bud>branch xylem>trunk xylem.Among them,the new root had the highest aluminum content,about 7.226g/kg.These results indicate that the root system and leaves of Camellia can accumulate a large amount of aluminum and store it in the cell wall,and both the xylem and phloem may participate in the transport of aluminum.（4）Effect of Camellia root H⁺secretion on its rhizosphere soil.Using hydroponic method,using annual camellia as the material,the experiment sets 4 different treatments,namely 0m M Al,1m M Al,0m M Al+0.01m M vanadate,1m M Al+0.01m M vanadate,to study the effect of aluminum on the activity of camellia H⁺-ATPase and root acid secretion;the results of the study showed that compared with the control,the acid secretion of the root system increased significantly in 1m M Al treatment,and the activity of Camellia root H⁺-ATPase increased 62.38%.Studies on the rhizosphere soil of camellia grown on acid soil in the field show that the root system of camellia can secrete a large amount of H⁺,thereby significantly reducing the p H of the rhizosphere of camellia.Through continuous extraction,the content of different forms of aluminum in the rhizosphere and extra-root soils of camellia was studied.It was found that the secretion of H⁺from the root of camellia affects the conversion between different forms of aluminum in the soil.From these results,it can be inferred that aluminum can induce a large amount of H⁺secretion in the roots of camellia,which is related to the activation of H⁺-ATPase.