Response Of Growth And Physiological Mechanism Of Three Shrub Species To Soil Petroleum Contamination

Petroleum pollution is serious in the oil production zone of northern Shaanxi Loess Hillsarea, and phytoremediation is an important technology for controlling petroleum pollution. Inthis paper, three shrub species such as Amorpha fruticosa, Hippophae rhamnoides andCaragana korshinskii are used as the research material. the methods of pot experiment andlaboratory analysis were adopted to research the dynamic changes of growth indexes, which isbased on the5levels of petroleum contaminated soil as0,5,10,15,20g oil per kilogram ofdry soil, then the dynamic changes of water status, osmotic regulation substances andantioxidant protection system were analyzed. The main conclusions are as follows:（1）There had no significant impact on the growth of all three shrubs on oil content of5g·kg-1, and the inhibitory effect on growth of C. korshinskii is greater than A. fruticosa and H.rhamnoides on oil content of10~20g·kg-1. According to comprehensive evaluation of thegrow index of three shrubs by the method of subordinate function, the growth response foranti-oil pollution of A. fruticosa is the best, followed by H. rhamnoides and C. korshinskii.（2）In the condition of keeping sufficient moisture for the soil, the water physiologicalindicators of A. fruticosa and H. rhamnoides, such as leaf water potential, leaf relative watercontent, PV parameters osmotic potential when saturated with water (ψssat)、penetrationpotential when expanded pressure is equal to zero(ψstlp)、relative moisture when expandedpressure is equal to zero(RWCtlp) and elative penetration water content(ROWCtlp), werereduced with the increasing of oil pollution.（3）In the condition of petroleum pollution, proline and soluble sugar in the A. fruticosacan be accumulated significantly, soluble sugar in the H. rhamnoides can also be accumulatedsignificantly. In the early stage of the C. korshinskii, the content of soluble sugar and solubleproteins appears high, but to the later stage, these two substances were reduced significantly.With the petroleum pollution aggravating, three shrub species all showed a certain osmoticadjustment ability, and oil contaminants would hamper the root water absorption severely,then resulting in continuing physiological drought for the three species.（4）In the oil content range of5g kg-1to15g kg-1, the activities of superoxidedismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR), and the contents of ascorbic acid (ASA) and glutathione (GSH) in A. fruticosa weremaintained or higher than the control, the activities of SOD and CAT, GSH and APX, GR,ASA in A. fruticosa has showed a good synergistic effect, but there is no accumulation ofhydrogen peroxide (H2O2) contents between each other. When the oil content reaches20g kg-1, the synergistic effect is weakened and plant growth is inhibited, and then growth of A.fruticosa can be influenced with the increasing of AsA content, so we can conclude that15g kg-1is the key threshold value of A. fruticosa tolerating petroleum contaminated soil.In lower oil contents (5and10g kg-1), antioxidant enzymes SOD, CAT, APX, GRactivity and antioxidants content of ASA and GSH were maintained or above the controlduring the whole growth period, there have been good synergistic effects not only between theactivities of SOD and CAT, but also between GSH and APX, GR, ASA activities in H.rhamnoides. there is no accumulation for H2O2contents. While at high oil contents (15and20g kg-1), the change of SOD activity were not consistent with CAT, and GR activity decreasedsignificantly, two kinds of collaborative effects were destroyed, then H2O2content increasedsignificantly and plant growth is affected. So the oil content of10g kg-1should be thethreshold value of H. rhamnoides tolerating petroleum contaminated of soil.In lower oil contents (5and10g kg-1), the SOD and CAT activities could keep stable oreven was increased, and showed a high collaborative effect in the early stage of the C.korshinskii growth. During the entire stress period of10g kg-1treatment, there is noaccumulation of H2O2contents in the whole growth period of C. korshinskii, due to the strongnon-enzymatic ASA action and the strong GR enzymatic action in late growth period. Whileunder the higher oil contents of15and20g kg-1in the early or mid-growth, activities of APXand GR remained stable or even increased significantly, ASA and GSH levels were alsosignificantly increased, and there are outstanding synergistic effects between APX, GR, ASAand GSH, at the same time, the non-enzymatic action of ASA and GSH were also increased,in spite of its still beyond the C. korshinskii scavenging ability, and leading to theaccumulation of H2O2, especially in the latter sampling period, the synergies among APX, GR,ASA and GSH and other clearance pathway were weakened, due to the GR activity and GSHcontent decreased, then the H2O2was largely accumulated and C. korshinskii growth was alsoseverely inhibited. Therefore, the treatment of10g kg-1should be the tolerance thresholdvalue of C. korshinskii to petroleum pollution of the soil.