Alleviative Effects And Mechanism Of Exogenous Siliconon Poplar Under Salt Stress

Soil salinization and alkalization is a cosmopolitan problem effecting entironment and sustainable development of agriculture.At present salt stress is one of the adversities for restricting yield of group,how to make use of wide salina and abundant salt water for developing agriculture is a important problem. Therefore,the investigation on the mechanisms of alleviating salt toxicity by silicon has been received more attention recently.This paper,Poplar clone,was used as a material in the study.Salt stress was created by adding Nacl.The possible function of exogenous silicon in salt stress was investigated by measuring and analyzing photosynthesis,lipid peroxidation,activity of various types of enzyme,X-ray electron probe microanalysis,leaf ultra-structure,ect. The main conclusions were drawn as following:1)With the increased of soil salt content,the growth of stem,the total biomass and the leaf physical of Poplar clone,were all decreased.When executes exogenous silicon into soil,the new breach grows long,the root activities increased,the leaves physiological chenged,Silicon improved the growth and physiology of Poplar clone.2)With the increased of soil salt content,the injure degree of chloroplasts of Poplar clone was strongly,the photosynthesis performance depressed under salt stress,applying silicon increased the plant photosynthesis performance. Photosynthetic pigment content,photosynthetic rate(Pn),stomatal conductance (Gs),and intercellular CO₂ concentration(Ci)of Poplar clone leaf were decreased, silicon can increase photosynthesis rate,It indicated that the addition of silicon under salt stress can maintain photosynthesis efficiency in leaves in a high level for the Poplar clone.3)It showed that the active oxygen metabolism balance of leaves was break under salt stress,the result showed that the activities of catalase(CAT)and peroxidase(POD)reduced gradually,the content of malondaldhyde(MDA) and relative permeability(RP)of plasma membrane decrease slowly with the arbuscular mycorrhizal fungi(AMF)mycorrhizal infected rate increased.In salt stress,applying silicon can increase the activities of catalase(CAT)and peroxidase(POD,and can reduces the content of malondaldhyde(MDA)and relative permeability(RP).It was implied that the damage by salt stress on Poplar clone be alleviated by silicon.4)The effects of silicon on ion distribution status of root tips under salt stress were studied with X-ray electron probe microanalysis.The results showed that the peak of Na⁺ and Cl^- the cells of the epidermis,cortex and stele under Nacl.stress was higher while that of K⁺ was lower.However,after the addition of silicon to the stressed plants,the contents of Na⁺ and Cl^- in those cells decreased remarkably while that of K⁺ increased significantly.Moreover,Na⁺ and Cl^- were distributed uniformly in all tissues of roots.It indicated that the addition of silicon under salt stress ameliorated the ion imbibtion and the ion micro-distribution status,therefore,it alleviated the toxic effects from saltions.5)The results of leaf ultra-structure showed that with increasing external Nacl concentration,the aging of chloroplasts was accelerated and the lamellae of the grana and stroma were disintegrated gradually under salt stress.The size and number of osmiophilic granule were increased.However,the addition of silicon under salt stress decreased the degeneration of membrane system was.It showed that the lamellae were lined regularly.The chloroplast granalamellae began to degenerate,The nucleus and mitochondria were well.