Study On Cd Accumulation And Physiological Change Rule In Clones Of Salix

Recently, ponderance of cadmium contamination has already endangered people's dailylife, phytoremediation that can renovate cadmium contamination soil is popular with itsparticular merit. Tree plant has a large number mass, strong root, no connection with food cycleand no recontamination. Tree plant is very important to renovate cadmium contamination soil.Salix has many varieties, fast growing, easy reproducing, good adaptability, it cantolerance salt and alkali, resist cold, drought and waterlogging, beautify environment andchange nature. Its strong root is good biological tilt, it can availably clear waste water awayindustry and living, absorb heavy metal from soil, has effect on renovating heavy metalcontamination soil, so it has practical significance for renovating cadmium contamination soilto select willow clones that can absorb a large number of heavy meatal and strong tolerance; ithas academic significance to study cadmium tolerance mechanism of willow.The study was focused on ability of accumulating cadmium, the effect on growing,physiology and biochemical under cadmium stress. The experimental material was Salixhybrid(seven clones) and Salix matsudana(sixteen clones), experimental way was hydroponicand soil culture. The study clarified trait of accumulate cadmium in Salix, announced basic onphysiology and biochemical of endurancing cadmium in Salix, made those clear that was ruleof absorbing and accumulating cadmium with time change in Salix, the changes on shape,chlorophyll, proline and dissolubility protein, antioxidant and enzyme for clearing oxygen oinunder cadmium stress, developed academic study on changing contamination environment byheavy metal with tree plant, provided new material and academic basis for renovatingcontamination environment by measue of zoology project, had practical significance forimproving level of environment and pepople's living.1 The rule of absorbing and accumulating cadmium in SalixWhen cadmium concentration was low in solution, the quantity of cadmium in leaf ofSalix was increasing with timing prolong, the speed of increasing was slowly before 15d andfast after 15d. when cadmium concentration was high in solution, the speed of increasing wasslowly before 10d and fast after 10d. The relativity between Cd accumulation of leaf and time of Cd stress accorded with equation that was c=0.005153 t^2.8629(under low concentration) andc=0.482934 t^2.0394(under high concentration), the speed of Cd accumulation in leaf was fasterunder high concentration. The ralitivity between Cd accumulation in leaf and concentration ofCd stress accorded with multinomial function model in hybrid Salix and power function modelin Salix matsudana.Cadmium quantity in different organs of hybrid Salix was root＞leaf≧shoot, it was root＞shoot≧leaf in Salix matsudana. The speed of accumulation in root was faster than shoot andleaf. The relativity between root and shoot was closer than that of leaf.When cadmium concentration was 20～100 mg·L^-1 in solution, cadmium content was4193～7888mg·kg^-1 in fresh root, 3077～8228mg·kg^-1 in old root, 752～972mg·kg^-1 in leaf,517～777mg·kg^-1 in shoot of hybrid Salix, transfer coefficient was 10%～17%; under the samecondition, it was 1991～4581mg·kg^-1 in fresh root, 3571～8644mg·kg^-1 in old root,330～492mg·kg^-1 in leaf, 367～551 mg·kg^-1 in shoot of Salix matsudana, transfer coefficient was7.4%～17%. The content of cadmium was increased from root to shoot and leaf with timeprolong and concentration increasing.2 Influence on plant growing of Salix under cadmium stressWhen cadmium concentration was low in solution, Salix growth was restrained nomarkedly, leaf fading green, but plant could survive normally. Tolerance of Salix on cadmiumgradually trail off with Cadmium concentration increasing, plant growth was restrained andmass was decreased markedly.When cadmium concentration was high(20～100mg·L^-1) in solution, the relativity betweenconcentration of Cd stress and plant hight accorded with model of Michaelis Mentent, andexponential model with diameter growth of plant.Poison symptom of Salix on cadmium first appeared in root, gradually expanded shoot andleaf. After a week in high Cadmium concentration, the top of newly root became brow, andexpanded all with time prolong, but shoot and root growing normally; after 15d, plant wasdwarf obvious, quality of newly shoot was reduced, the top of shoot became black, new leafwas yellow and thin, leaves defoliated a little.the extent of poison symptom was differentamong varieties and clones. Poison symptom first appear brow spot in leaf, expanding whole leaf with time prolong so as to wilt and death. Relativity between plant growth and Cdconcentration accorded with exponential function model. Influence on plant growth in hybridwas less than in Salix matsudana.When cadmium concentration was 100 mg·L^-1～200 mg·L^-1 in solution and wthin 15d, Salixwas dead.3 Influence on chlorophyll in leaf under cadmium stressIt had dual effect on change of chlorophyll by time and concentration of cadmium stress,when the time was shorter and concentration was low, chlorophyll producing was faster withCadmium stimulating, when the time was longer and concentration was higher, chlorophyllproducing was controlled. When cadmium concentration was 20 mg·L^-1and within 10d, contentof chlorophyll was increased, and will be decreased with time prolong and concentration ofcadmium. The change of chlorophyll a was acuter than chlorophyll b.4 diversities of Cd tolerance among clones and change of physiologyin leaf under cadmium stressContent, mass and magnitude of Cd accumulation in overground organ and root,chlorophyll in Salix were heritable with Cd tolerance under Cd stress. Ten clones of Salixmatsudana were analysed by tolerance index of seven character, the sequence of Cd tolerancewas NO. thirteen＞NO.eight＞NO. sixteen≈NO.eighteen≈NO.nine＞NO.two≈NO.four＞NO.ten＞NO.three＞NO.five.When Cd concentration was 10～150 mg·kg^-1 in soil, plant hight, total chlorophyll,conductance, content of proline and dissolubility protein in hybrid Salix were were heritablewith Cd tolerance under Cd stress, five clones of hybrid Salix were evaluated by toleranceindex of the five character, the result was NO.five＞NO.six≈NO.two＞NO.seven＞NO.four.When Salix was stress by cadmium, plant growth of was restrained and mass wasdecreased, content of chlorophyll and dissolubility protein and conductance was reduced,conten of MDA was increased, change of proline has no rule. Relation among indicators waschanging with concentration of cadmium stress. 5 Change of content of antioxidant and activity of antioxidantionenzyme in leaf of Salix under cadmium stressUnder cadmium stress content of ASA, activity of POD, CAT, APX and GR in leaf of allclones was increased with time prolong and concentration increasing of cadmium stress.Content of GSH and activity of SOD were increasing and decreasing sometimes, change ofNPT was a little under Cd stress.Positive relativities were most prominent between content of ASA and activities of APX,minus relativities were most prominent between activities of GR and CAT in 15days undercadmium stress. Positive relativities were prominent between SOD and ASA, GR and CAT, GRand APX, minus relativities were prominent between GSH and CAT, GSH and APX. Positiverelativities were most prominent between APX and CAT in 30 days under cadmium stress.6 Change of electrophoretic bands of isosyme and protein in leaf ofSalix under cadmium stressUnder cadmium stress, bands of SOD in 0.49 of mobility were disappeared on leaf of NO.four and five, and were strengthen on leaf of NO. sixteen; Bands of SOD in 0.63 of mobilitywere weaken on leaf of NO. five and sixteen, and were strengthen on leaf of NO. four.Under cadmium stress, bands of POD in 0.84 of mobility were strengthen on leaf of NO.sixteen, a weak band were appeared in 0.84 of mobility on leaf of NO. four, bands of POD in0.84 and 0.74 of mobility were weaken on leaf of NO. five.Main bands of protein of Salix matsudana had seven strips, molecular weight was about14.2～116KD. Bands of protein in 14.2KD were weaken on leaf of NO. four, Bands of proteinin 14.2KD and 36.2KD were strengthen on leaf of NO. sixteen, nearly no change on leaf of NO.five.