| In order to understand the potential of remediation of Sr and diesel in soil by woody plant, the physio-biochemical responses of Populus cathayana, Populus alba and Populus russkii to Sr and diesel stress were studied. The treatments were as followed:(1)different concentration of Sr2+ respectively(both for 0, 10 mg·kg-1, 100 mg·kg-1);(2)combination of diesel and Sr2+(15 mg·kg-1diesel, 15 mg·kg-1diesel+10 mg·kg-1Sr2+, 15mg·kg-1 diesel +100 mg·kg-1 Sr2+). Each treatment was sampled after 30 d and 60 d respectively. Results were shown as followed:(1) Under Sr stress, the height, stem diameter and leaf area of P. cathayana, P.alba and P. russkii seedlings increased at first and then decreased with the increasing of Sr concentration. Chlorophyll content, maximal PSII efficiency(Fv/Fm), the quantum yield for electron transport of PSII(Φ(Eo)) and the probability that a trapped exciton moves an electron into the electron transport chain beyond QA-(Ψo) also decreased after rising. The results indicated that the chlorophyll content and PSII reaction center were promoted under 10 mg·kg-1Sr2+stress but inhibited under 100 mg·kg-1Sr2+stress. With the increasing of Sr concentration, evapotranspiration rate(E), stomatal conductance(Gs) and photosynthetic rate(A) of P. cathayana, P. alba and P. russkii increased at first and then decreased while the intercellular CO2 concentration(Ci) had a trend of increase. It showed that Sr inhibit the photosynthetic rate by non-stomatal factors. The change of malondialdehyde(MDA) content was not significant, but the activities of POD, SOD and APX increased at first and then decreased, it showed that Sr increased the oxidative stress level. Pro content increased and it indicated that seedings replied the Sr stress by accumulating proline. The E, Gs and A of P. cathayana have been affected less and its tolerance of PSII reaction center, electron transport chain,chlorophyll content and antioxidase activities to Sr stress were stronger.(2) Under Sr and diesel stress, the growth indexes and chlorophyll content of P.cathayana, P. alba and P. russkii were lower than the seedings that under Sr stress alone observably and P. alba was affected less. It showed that the growth of P. alba was inhibited less by diesel than P. cathayana and P. russkii. Under Sr and diesel stress, the E, Gs and A of P. cathayana, P. alba and P. russkii were lower than which under Sr stress alone. Diesel inhibited the photosynthetic rate by stomatal factors at first and then non-stomatal factors. It indicated that diesel may damaged the photosynthetic structures of seedings. Under Sr and diesel stress, the malondialdehyde content of P. Cathayana was higher than seedings that under same Sr stress significantly but the change of P.alba and P. russkii were not significantly. It showed that diesel led membrane lipid peroxide leve to increase in P. cathayana. Under diesel stress, the activities of urease,invertase, acid phosphatase and alkaline phosphatase in soil of P. cathayana, P. albaand P. russkii increased observably. It possibly because of that microorganism could use the diesel as source of carbon, energy and activate enzyme and it could relieve Sr stress in soil.(3) Male P. cathayana were stronger than female in all treatments. Sr inhibited the chlorophyll content and SOD activity of female P. cathayana. Sr accelerated the chlorophyll content and SOD activity of male P. cathayana with low concentration but inhibited them with high concentration. With the increasing of Sr concentration, MDA content of male and female seedings increased and the change of female seedings was more marked. female P. cathayana were more sensitive than male and male seedings had a stronger tolerance to Sr stress. Under Sr and diesel stress, PSII reaction center and chlorophyll content of female P. cathayana were more sensitive than male seedings, it indicated that male P. cathayana had a stronger tolerance to diesel under the same concentration of Sr.(4) The enrichment concentration of Sr increased with the increasing of Sr concentration. Root and leaf were the major enrichment organs and the ability sequence of enrichment concentration was: leaf > root> stalk. Under 100 mg·kg-1Sr2+stress, the root enrichment concentration of Sr of P. Alba, P. russkii and P. cathayana were:0.836 mg·g-1·DW-1, 0.568 mg·g-1·DW-1 and 0.359 mg·g-1·DW-1. Leaf enrichment concentration of Sr of P. Alba, P. russkii and P. cathayana were: 0.942 mg·g-1·DW-1,0.787 mg·g-1·DW-1 and 0.543 mg·g-1·DW-1. The ability sequence of enrichment concentration was: P. alba > P. russkii > P. cathayana. Although the enrichment concentration of P. cathayana was lower, it had a stronger tolerance to Sr stress and it also had higher ability to transport Sr under 100 mg·kg-1 Sr2+ stress. So it can be used as a reference tree species for high enrichment ability of strontium. Under combined stress of diesel and Sr, enrichment ability of P. alba was most strong. In consideration of its stronger tolerance to diese, P. alba is more suitable for remediation of Sr and diesel combined pollution. Although the leaf enrichment concentration, S/R and L/R of male P.cathayana were larger than female under Sr stress, male P. cathayana had a stronger tolerance and transport ability under combined stress of diesel and Sr. |
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