Study On The Response Mechanism Of Salix Matsudana Growth Process Under Lead Stress

Heavy metal pollution of the soil has become a worldwide ecological problems. Lead is a common heavy metal pollutants, when it enters the body and accumulate in the plant inside, will adversely harm plants slowly. Plant have functions of absorption, evaporation, filtration root, degradation, stabilization and so on,and it has a powerful purification to the soil and water. Phytoremediation of environmental pollution as a clear green technology has great development space, more and more experts pay attention to it. Salix (Salix matsudana) as the Salicaceae Salix deciduous tree, is one of the world's largest species. Which has a wide distribution, adaptability, fast growth, high biomass, heavy metal tolerance ability and other characteristics, become a dominant species to research heavy metal tolerance.Through pot experiment to study the stress when Salix roots in exposure to lead, stems, leaves enrichment transport characteristics, response of morphological, physiological and biochemical indexes, by scanning and transmission electron microscopy (STEM), EDS (EDAX), Fu Fourier infrared spectroscopy (FTIR) analysis of Salix lead stress that when the root, stem, leaf morphology, distribution of mineral elements, changes in the composition of the active group. System analysis of Salix Pb stress mechanisms. Salix year in the spring and summer growing season is measured, results are as follows:(1) Salix enrichment of lead, transport feature:Salix enrichment and transport as well as the ability to lead Salix height, root length and biomass increased with increasing concentrations of lead increased first and then decreased, up to a maximum value at 600 mg/kg. Effects of lead stress on root, stem Salix lead content enrichment transfer coefficient and morphological characteristics of the summer was significantly higher than in the spring.(2) Morphological, physiological and biochemical changes in Salix Indexes:Root and stem of SOD, POD, CAT activity, soluble protein content and chlorophyll content of leaves increases the concentration of lead in the soil increased first and then decreased, MDA content showed an upward trend. Salix roots mainly involving the site of heavy metals lead, only small amounts of lead to the transfer of part of the ground. Salix ability to lead resistance as follows:root> stem> leaf. Roots lead concentration 200 mg/kg SOD,2.2 and 3.75 times higher than the control group, the activity of POD; CAT activity, chlorophyll content, soluble protein content in lead concentration of 600 mg/kg up to a maximum value; root MDA content much larger than the increase stems. Studies have shown that:Salix optimal tolerance for lead concentration of 600 mg/kg. Lead concentrations in the low zone, summer effects of lead stress on SOD, POD, CAT activity, chlorophyll content, soluble protein content was significantly higher than in the spring; but high lead concentration region, spring is significantly higher than in summer. Effect of lead stress on MDA content in summer was significantly higher than in the spring.(3) Salix roots, stems, leaves microstructure change:Scanning electron micrographs show that Salix roots, stems, leaves in lead concentration of 600mg/kg remain relatively intact microstructures. High concentrations of lead to make root and stem Salix deformed or blocked, the blade structure from the normal state into the fold expansion of convex shape. Explained lead concentration of 600mg/kg, the Salix maintain good growth state, the normal absorption and transport of the desired substance.(4) Salix roots, stems, leaves active group composition changes:By the Fourier transform infrared analysis shows that the root is the major site of lead resistance. After the lead stress, the root of the oxygen-containing reactive hydroxyl groups-OH bond, and carbonyl peaks -C=O-bonds weaken or even disappear, and the lead concentration of 600mg/kg when the roots peak weakening or disappearance of the most antioxidant capacity strongest. Aboveground active groups did not change significantly, indicating that the main roots of the ability to lead enriched, upward transport of lead is weak.(5) Salix root, stem and leaf mineral elements distribution:Lead concentration of 600mg/kg, the Salix roots, stems, leaves inclusive of Pb, indicating Salix lead up to the best transport capacity at 600mg/kg. At low concentrations, Salix roots, stems, leaves Ca, Na element Salix promote growth and enhance photosynthesis. Leaves S elements play a role so that at low concentrations of metallothionein (MT) expression increased, but the concentration is too high, by inhibiting the expression of MT.