The Growth And Physiological Characteristics Of Paulownia Kawakamii Resisting Of Lead And Zinc

The effects of lead (Pb) stress on seed germination of Paulownia kawakamii wasstudied in this paper which was grown in petri dishes in incubator.The seedlingscultivated in nutrient solution and the growth, physiological index and its metal ionuptake was tested under the Pb stress and its complex stress of Zn and Pb, the resultsshown as follow.1Effects of lead stress on seed germination of P. kawakamiiThe research of the effects of Pb stress on the germination of P. kawakamii seeds isby culture dishes in man-made climate equipment. The results present that: negativeeffect is shown when different concentration of Pb stress on the seed germination of P.kawakamii. This can significantly reduce the germination rate， germination energy，germination index， the length of cultured root and fresh weight of single plant， andcan reduce the germination pace， delay its initial germination time. When the leadconcentration reaches300mol/L the lowest germination rate can be found，and thegermination rate decreased by26.8%by contrast with those which germinate in normalcondition， while the50mol/L，100mol/L concentration of Pb stress performancecertain benefit on the germination rate of the seeds of P. kawakamii.Seed germinationneeds longer time in higher concentration. Sixteen days is needed when the seedsgerminate in the concentration of200mol/L，300mol/L of treatment solution. Thegermination index decreases with the increasing concentration of Pb stress. Thegermination index is the lowest in Pb300mol/L. The index is decreased by81.3%bycontrast with those which germinate in normal condition. This shows that the seeds getdeterioration before its germination force lost in the higher concentration of stress.Complete inhibition is shown in Pb stress on seed radicle growth. The fresh weight ofsingle seedling shows that plant growth situation is inhibited by high concentrations ofPb.2Effects of lead stress on the growth and physiological index of P. kawakamiiEffects of Pb treatment liquid on the growth and physiological index of P.kawakamii have been studied by15d liquid culture. The results show that: with theincreasing of concentration of Pb the growth of plants is decreased，tolerance index ofits root less than0.1. This indicates that maladjustment has been appeared to the plant.The photosynthetic pigment contents of leaf are decreased with those contrast plantsunder the single factor of Pb stress. Higher concentration of treatment liquid has inhibited the forming of chlorophyll in plant and destroyed the structure of chlorophyll.MDA content of the aboveground part of P. kawakamii is significantly decreased withthe increase of the concentration of Pb，but the content is higher than that of the contrastplant. MDA content is the highest in the25mol/L of concentration of Pb. It is increasedby64.7%contrast with those which grow in normal condition. The content of GSH inthe aboveground part of P. kawakamii decreases at first and then increases and1times isdecreased at the concentration of50mol/L by comparing to contrast plant. GSH contentof the underground part of the plant is downward trend by overall comparing to contrastplant，and1.33times is decreased when the concentration is25mol/L comparing to thecontrast plant.The activity changes of POD in the part of aboveground are become moreactive when Trichloroacetic acid of20%added to it.The variation trend is not obviouswhen content of ASA defense against the toxicity of reactive oxygen with theconcentration of Pb increased. The trend is downward basically. This indicates that theability of the body defenseagainst the toxicity of reactive oxygen is reduced.3The effects of compound stress of lead and zinc on growth and physiologicalindex of P. kawakamiiEffects of Pb and Zn compound treatment liquid on the growth and physiologicalindexes of P. kawakamii have been studied by15d liquid culture. In compoundtreatment of different concentrations of Pb and Zn，the plant growth with downwardtrend overall by comparing to the contrast plant，and the root，stem length and freshweight of ground and under ground part decreases with the increasing of concentrationof Zn in the composite treatment. Chlorophyll a，chlorophyll b were increasedcomparing with contrast plant under the condition of single factor of the100mol/LPbtreatment liquid，and chlorophyll a，chlorophyll b content ware decreased obviouslycomparing with contrast plant under the condition of the other treatment liquid，and thecarotenoids decreased in Pb and Zn composite stress. MDA Content in P. kawakamiileaf is increased to the maximum of90%，87.8%respectively under compound stress of100mol/LPb and200mol/LZn，200mol/LPb and200mol/LZn，by comparing to contrastplant. The Pro activity of P. kawakamii is decreased under compound treatment ofdifferent concentrations of Pb and Zn.Pro activity of parts of the aboveground andunderground is the lowest under the composite stress of200mol/LPb and200mol/LZn.It is decreased by82.2%，70%respectively comparing to contrast plant.The anti-ascorbicacid content in stem and leaf of P. kawakamii is rising under the single factor andcomposite stress of Pb and Zn comparing to contrast plant. The anti-ascorbic acid content in roots was lower than that of the contrast plant. It shows that the defense ofactive oxygen toxicity is decrease in root.4Effects of lead and compound pollution of lead and zinc on metallic ionaccumulation of P. kawakamiiThe dry weight of root，stem and leaf of P. kawakamii Ito decreases with theincreasing of different concentrations of Pb and Pb，Zn composite stress. Plant growth isinhibited by higher concentration of Pb，Zn stress.The content of the root of P.kawakamii uptake of Pb ion increased significantly with the concentration increasingwhen P.kawakamii is in different concentrations of Pb treatment liquid. Pb uptake ishindered by Pb，Zn composite stress on the plant. Increased Pb concentration can makethe absorption of the contents of Zn of the plant decreased，and the performance is ofroot> stem> leaf. Cu ion content in P. kawakamii a roots is inhibited by higherconcentrations of Pb. Pb and Zn composite stress can promote the absorption of Cu ionin the stem of P. kawakamii.With the increase of the concentration of Pb and Zn theperformance of absorption Ca ion by P. kawakamii is: stem> leaf> root.This shows thestrong ability of P. kawakamii ion transfer and conversion in vivo.With the increase ofconcentration of Pb in the test the absorption Cd ions of root of P. kawakamii isinhibited in high Pb concentration，similar to the absorption of K ions. The variation ofabsorption of Na ion content of stems (rod) is not significant under Pb single factorstress，but more obvious under Pb，Zn composite stress.