| Aleurites montana is an excellent woody oil plant in China.It is a multi-functional tree and has been widely planted in the south,especially in Fujian Province.It is planted on a large area of red soils at hilly regions in northern Fujian.The soil is acidic and rich in active aluminum.In recent years,these areas have been seriously affected by acid rain,further releasing active aluminum from the soil.The resulting aluminum toxicity is harmful to the growth of Aleurites montana,the yield and quality of fruit are also affected.In view of this,this study used la seedlings of Aleurites montana as materials,to study the effects of different concentrations of aluminum on the growth and physiological and biochemical indexes of Aleurites montana using Hydroponics and soil culture methods,and to examine the response mechanism of Aleurites montana to aluminum.By studying the distribution pattern of nutrient elements in roots and leaves of Aleurites montana,the effects of aluminum stress on nutrient absorption and transportation in Aleurites montana were analyzed,in order to provide a scientific basis for the high-quality aluminum toxicity treatment of plantations.The main results are summarized as follows:1.Effect of aluminum stress on the root morphology and physiological traits of Aleurites montanaOverall,aluminum had a significant effect on the total root length,total root surface area,number of root tips,number of branches,root length density,root surface area density,and specific root length of seedlings grown in hydroponic culture.Aluminum had extremely significant inhibitory effect on the average root diameter of hydroponic seedlings.On the other hand,aluminum had a certain promoting effect on the specific root length of the seedlings of soil culture,and had an inhibitory effect on the root tissue density.For the roots of the soil-cultured seedings of Aleurites montana,at aluminum concentration of 120 mg·kg-1,aluminum significantly increased activities of SOD,POD,CAT and content of MDA.However,when the concentration of aluminum was 320 mg·kg-1,activities of POD and CAT were decreased,and activity of SOD and content of MDA were significantly increased.The soluble protein of the roots decreased when the aluminum concentration was 30 mg·kg-1,but increased when the aluminum concentration was 320 mg·kg-1.However,the content of pro line and soluble sugar in roots had an obvious reduction in response to aluminum treatment.In general,for the roots of the hydroponicseedlings of Aleurites montana,aluminum tended to significantly reduce activity of SOD,content of MDA and soluble protein.Low aluminum environment promoted activities of POD,CAT and content of proline,while high aluminum environment had a significant inhibitory effect.On the whole,under different gradients of aluminum treatment,the contents of lactic acid and malic acid in the roots of the soil-cultured seedlings of Aleurites montana were extremely reduced,and tartaric acid content was slightly increased.When the concentration of aluminum was 320 mg·kg-1,the content of oxalic acid,acetic acid and fumaric acid in the soil-cultured seedings increased significantly,but the content of citric acid decreased significantly.Aluminium stress significantly promoted the increase of oxalic acid in root of hydroponicseedlings of Aleurites montana.When the aluminum concentration was 30～180 mg·L-1,it could promote the secretion of lactic acid.When the aluminum concentration was 30 mg·L-1,the acetic acid content was significantly promoted.When the aluminum concentration was 70～320 mg·L-1,the secretion of acetic acid was limited.2.Effect of aluminum stress on the leave morphology and physiological traits of Aleurites montanaThe results showed that after treatment with different gradients of aluminum,the MLA of soil-cultured seedlings of Aleurites montana was not significantly different,and the SLA significantly increased,while the LDMC significantly decreased,showing an opposite trend to the former.After hydroponicseedlings of Aleurites montana were under aluminum stress,the SLA at the aluminum concentration of 180 mg·L-1 was significantly higher and the LDMC was significantly lower.When the aluminum concentration was 320 mg·L-1,the SLA decreased while the LDMC increased significantly.There was a significant increase in MLA overall.Under severe aluminum stress,aluminum significantly inhibited the Fv and Fm of soil-cultured seedlings of Aleurites montana,but significantly promoted the Fv and Fm of hydroponicseedlings.Aluminum also had a certain role in promoting the chlorophyll content of soil-cultured seedlings.Overall,aluminum had a certain inhibitory effect on photo synthetic rate,stomatal conductance,intercellular CO2 concentration,and transpiration rate of seedlings of Aleurites montana,while it promoted water use efficiency to some degree.For the soil-cultured seedlings of Aleurites montana,aluminum promoted the increase of MDA and soluble protein in leaves at lower aluminum concentration,and when the aluminum concentration was higher,it had an inhibitory effect.The change of soluble sugar in leaves was the opposite,which decreased in the low aluminum environment and increased in the high aluminum environment.Regardless of low or high aluminum environment,the content of pro line,activities of POD and CAT in leaves all increased,and the activity of SOD in leaves decreased.For the hydroponicseedlings of Aleurites montana under aluminum treatment,the contents of MDA and soluble protein in leaves decreased,while the contents of pro line,soluble sugar and activity of SOD in leaves increased.When the aluminum concentration was 70 mg·L-1,the activity of POD in the leaves increased significantly,but the activity of CAT in the leaves decreased significantly.When the aluminum concentration was 250 mg·L1,the activity of POD in leaves decreased,butthe activity of CAT in leaves increased significantly.3.Effect of aluminum stress on plant growth of Aleurites montanaThe results of this study indicated that low-aluminum environments maily had favorable effect on the plant growth of soil-cultured seedlings,while high-aluminum environment mainly had suppressed effect.The promotion of low-aluminum environment on roots of soil-cultured seedlings was more significant than that of leaves,and the inhibitory effect of high-aluminum environment on roots was more pronounced than that of leaves.Under different gradients of aluminum treatment,the growth rate of height and ground diameter,and root/shoot ratio of hydroponicseedlings decreased,while the ratio of aboveground biomass to total biomass increased.When the aluminum concentration was 120 and 180 mg·L-1,the roots,stems,leaves and total biomass of the hydroponicseedlings all increased.When the concentration of aluminum was 320 mg·L-1,the roots,stems,total biomass and root/shoot ratio all decreased significantly,and the biomass of the leaves also decreased.The results showed that the plant growth of hydroponicseedlings of Aleurites montana was mainly inhibited by aluminum.4.Effects of aluminum stress on the absorption and transport of aluminum and mineral elements in Aleurites montanaUnder aluminum stress,the content of aluminum in leaves of soilcultured seedlings of Aleurites montana was higher than that of the control when the concentration of aluminum was 30～250 mg·kg-1,but lower than that of the control when the concentration of aluminum was 320 mg·kg-1.However,the content of aluminum in roots was generally higher than that of the control.When the concentration of aluminum was 320 mg·kg-1,the content of aluminum in leaves decreased significantly compared with the control,while the content of aluminum in the roots increased significantly.After hydroponicseedlings of Aleurites montana were under aluminum stress,the content of aluminum in the leaves decreased as a whole,while the content of aluminum in the roots increased obviously.The content of aluminum in leaves and roots increased first and then decreased with increasing aluminum stress.For soil-cultured seedlings of Aleurites montana,the effect of aluminum on the C,P and Mn elements in leaves was mainly adverse,and the effects of aluminum on the N,K,Mg,Ca,Fe,Zn,and Cu elements in leaves were mainly favorable.The effects of aluminum on the K,Mg,Fe,Mn,Cu and Zn elements in the roots were mainly promoting.For the C and Ca elements of roots,they had a limiting effect in the low-aluminum environment,but were promoted in the high-aluminum environment.The effect on P of the roots was only promoting when the aluminum concentration was 30 mg·kg-1,and other treatments all showed inhibitory effects.For hydroponicseedlings,aluminum maily had suppressive effect on C,Ca,Fe,and Mn elements in leaves;and promoting effects on N,P,K,Mg,Zn,and Cu elements in leaves.Aluminum had extremely significant inhibitory effect on C,Ca,and Mn elements in roots,and mainly promoted P and K elements in roots.The N,Mg,Fe,and Cu elements in the roots were elevated in the low-aluminum environment and suppressed in the high-aluminum environment.The Zn element in the roots was lower in the low-aluminum environment,but higher in the high-aluminum environment. |
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