Studying On The Physiological Basis Of Fe²⁺,Zn²⁺ Nutrition In Leymus Chinensis

Leymus chinensis is a perennial plant of the gramineous family.It is an important constructive species of meadow steppe and typical steppe in eastern Eurasia and the main wild forage for grazing livestock.The content of iron and zinc in Leymus chinensis leaves directly affects the nutrition of iron and zinc in grazing livestock.At present,the mechanism of Fe and Zn dependent growth of Leymus chinensis and the formation of Fe and Zn content in leaves are unknown.This paper makes a systematic study on these two problems,which provides a basis for in-depth study of the role of Fe²⁺and Zn²⁺in plant growth and development at the molecular level,Eventually meet the iron and zinc nutritional needs of livestock.The experiment of Leymus chinensis in different periods was mainly carried out through two methods of culture medium and hydroponic culture.The relevant results are as follows:（1）The high concentration of Fe²⁺（20×）medium significantly inhibited the root and leaf growth,root hair development and the accumulation of Ca,Zn,Mg and K in Leymus chinensis seedlings.Increasing the concentration of Zn²⁺,Ca²⁺,Mg²⁺and K⁺in the medium did not change the inhibitory effect of high concentration of Fe²⁺on the growth of Leymus chinensis seedlings.（2）Deficiency of Fe²⁺（0×）and high concentration of Zn²⁺（20×）hydroponic solution significantly inhibited the growth and chlorophyll content of Leymus chinensis seedlings,promoted the accumulation of Zn,Mg,K and Ca,Mg,K in Leymus chinensis leaves,and inhibited the accumulation of Fe respectively.Increasing the concentration of Mg²⁺in Fe²⁺（0×）deficient hydroponic solution could significantly restore the inhibition of Leymus chinensis leaf growth induced by Fe²⁺deficiency,but did not change the chlorophyll content.Increasing the concentration of Fe²⁺in high concentration Zn²⁺（20×）hydroponic solution can restore the inhibitory effect of high concentration Zn²⁺on the growth of Leymus chinensis.The high concentration of Fe²⁺（20×）hydroponic solution significantly promoted the growth of roots and leaves of Leymus chinensis,and inhibited the accumulation of Ca,Zn and Mg in leaves.（3）Seedlings of Leymus chinensis were treated with high concentration Fe²⁺（20×）medium for 48 hours,the activities of Peroxidase,Superoxide dismutase,catalase,Ferric chelate reductase,Ascorbate peroxidase,Glutathione reductase and the contents of Malondialdehyde,Dehydroascorbic acid and Reductive glutathione in roots increased significantly.In the meanwhile the gene expression of nicotinamide synthase and peroxidase was significantly down-regulated,and the plant germinin-like protein gene was significantly up-regulated.The seedlings of Leymus chinensis were treated with deficiency of Fe²⁺（0×）hydroponic solution for 48 hours,the activities of Peroxidase,Superoxide dismutase and the contents of Dehydroascorbic acid,Reductive glutathione in leaves increased significantly.The colorless anthocyanin dioxygenase gene and alternative oxidase gene were significantly down-regulated and up-regulated.（4）The seedling of Leymus chinensis were treated with deficiency of Fe²⁺（0×）and high concentration of Zn²⁺（20×）hydroponic solution.With the increase of treatment time,the net photosynthetic rate,respiration rate,Fv/Fm,actual photosynthetic quantum yield under light and electron transfer rate of PSI,the maximum photochemical quantum yield,electron transfer rate and photochemical quenching coefficient of PSII showed a significant downward trend.The dissipation caused by donor side limitation of PSI,quantum yield of regulatory energy dissipation of PSII and the non-photochemical quenching coefficient increased significantly.