Effect Of Lead Stress On The Growth And Physiology Of Tabebuia Impetiginosa

As an ornamental,economic and medicinal plant,Tabebuia impetiginosa has great potential development and utilization after introduced into China.The plant were growed in Guangdong,Guangxi,Fujian,Hainan and other regions.Lead is extremely harmful,difficult to degrade and the damage cannot be reversed.As the environment is generally polluted,we study the response mechanism of Tabebuia impetiginosa under lead stress,which has the great significance and theoretical knowledge for the development of seedling and cultivation.In this experiment,as the test materials of annual Tabebuia impetiginosa seedlings,which were teated for four different lead concentrations(0,1000,3000,5000mg·kg-1).By measuring the response under different treatments on its growth,physiology,and lead transfer and enrichment,we analysis its resistance to heavy metal Pb within a certain range..The results show:1.Under different concentrations of lead treatment,the growth index of Tabebuia impetiginosa is different.The relative increment of plant height,the relative increment of ground diameter,the biomass of each part,the area of specific leaf,the total root volume,the total root area and the total number of root tips all increased first and then decreased with the increase of lead concentration,at T1(1000mg·kg-1)The highest value occurred during treatment,which was significantly different from that of the control group.The relative increment of plant height and the relative increment of ground diameter were the lowest in the T2(3000mg·kg-1)treatment group,T3(5000mg·kg-1)There was a slight increase in the treatment group of,but the difference was not significant compared with T2;the other indicators decreased with the increase of lead concentration.The difference between the lowest value of T3 treatment and the control group was significant.The increase in lead concentration gradually decreased,and the difference between treatments was not significant.2.Under different concentrations of lead treatment,the physiological indexes of Tabebuia impetiginosa seedlings changed as follows:the relative conductivity,MDA,soluble sugar and soluble protein content decreased first and then increased with the increase of lead solution concentration,the lowest value Appeared in the T1(1000mg·kg-1)treatment group,the highest value appeared in the T3(5000mg·kg-1)treatment group,and the difference was significant with the control group;the free proline increased first with the increase of lead concentration.After the treatment,the content of SOD was the highest when treated with T1(1000mg·kg-1),and decreased with the increase of lead treatment concentration.The treatment with T3(5000mg·kg-1)was the smallest,and the difference was significant compared with the control CK;POD and CAT did not change much when the concentration of lead solution was 1000mg·kg-1,and then increased with the increase of lead concentration.The maximum value appeared in the T3 treatment group,which was significantly different from the control group.The photosynthetic characteristics of Tabebuia impetiginosa under different lead treatments were different.The chlorophyll fluorescence parameters Fo,Fm,Fv/Fm and Fv/Fo increased first and then decreased with the increase of lead concentration,and were treated at T3(5000mg·kg-1).The time is the minimum value,which is significantly different from the control group,but Fo and Fm have the highest value in T2 treatment,and the highest values of Fv/Fm and Fv/Fo appear in T1 treatment;under different lead concentrations,net photosynthetic The trends of rate,transpiration rate,stomatal conductance and intercellular CO2 concentration were consistent.The same as chlorophyll fluorescence,the first increase and then decrease,the maximum and minimum values appeared in T1 and T3 treatment,respectively,and were significantly different from the control group CK.3.Under different concentrations of lead solution,the change of lead content in the organs of Tabebuia impetiginosa seedlings was consistent with the lead concentration.The difference between the treatments was significant.The lead content in the underground part was much higher than that in the aboveground part.The amount of lead is root>stem>leaf.The transport capacity of lead seedlings under different treatments was basically the same,the transport coefficient was between 0.08-0.11,the enrichment factor decreased with the increase of lead concentration,and the enrichment coefficient of underground part was significantly higher than that of aerial part.According to the analysis of various indicators,under the treatment of 1000mg"kg-1 lead solution,,the concentration is increased to 3000-5000 mg·kg-1,the seedlings of Tabebuia impetiginosa were subjected to certain stress,which inhibited the growth of seedlings,and the index of lead enrichment also decreased,but the growth state remained normal,indicating that Tabebuia impetiginosa has a certain lead on lead.Resistance and tolerance,introduction and planting can be carried out in relevant lead-contaminated areas.