Selenium Tolerance Characteristics Analysis Of Se-hyperaccumulator In Cardamine Hupingshanensis

Selenium is an important substance to maintain the normal function of the human body,which can prevent the occurrence of many diseases,but excessive selenium will have toxic effects on the human body.Asfor plants,selenium is also a beneficial element,but excessive selenium can also be toxic to plants.Se-hyperaccumulators can tolerate high concentrations of selenium,and they have the ability to absorb and assimilate a large amount of selenium.This characteristic of this plants can be used to provide organic selenium for selenium-deficient areas,so it is important to study the selenium tolerance characteristics of Se-hyperaccumulators.In this study,the Se-hyperaccumulator plant cardamine(Cardamine hupingshanensis)was used as materials.The effects of different valence selenium(selenite Na₂Se O₄,selenite Na₂Se O₃)and concentrations on growth(plant height,root length,fresh weight,dry weight),selenium content,root morphology(total root length,total root surface area,total volume,root tip number,root length of different diameters and root average diameter),physiological indexes(SOD,POD,CAT,chlorophyll content,soluble sugar content and MDA content)were analyzedtoclarifying the mechanism of selenium tolerance of cardamine,as well as exploring selenium-rich gene resources for selenium-rich molecular breeding design and plant treatment of selenium pollution.The main results are as follows:(1)Treated with 30mg/kg Na₂Se O₄,the growth indexes(plant height,root length,aboveground fresh weight,underground fresh weight,aboveground dry weight,underground dry weight)reached the maximum.Treated with210mg/kg Na₂Se O₄,the above growth indexes reached the minimum.Treated with 30mg/kg Na₂Se O₃,the plant height,root length,aboveground fresh weight,underground fresh weight and aboveground dry weight reached the maximum.Treated with 60mg/kg Na₂Se O₃,the dry weight of underground part reached the maximum.Treated with210mg/kg Na₂Se O₃,the growth indexes of cardamine reached the minimum.(2)The selenium content of cardamine crudely increased with the increase of selenium treatment concentration.When the treatment concentration exceeded the tolerance threshold,the selenium content gradually decreased.The selenium content in the overground part is always higher than that in the underground part.Under Na₂Se O₄ treatment,the maximum selenium content in the ground and underground parts of cardamine was 1942.2 and 1555.68 mg/kg,according with the standard of Se-hyperaccumulator(>1000mg/kg).However,the maximum selenium content in the ground and underground parts of it was 680.78 and 368.50 mg/kg with the Na₂Se O₃ treatment,according with the standard of selenium-enriched plants(100-1000mg/kg).(3)Treated with 30-60mg/kg Na₂Se O₄and Na₂Se O₃,the total root length,total volume and the number of root tips,the total surface area of root,the length of root diameter in 0-0.5mm,0.5-1mm,1-1.5mm reached the maximum.Treated with210mg/kgs,the above indexes were the lowest.Selenium has nosignificant effect on root length and average root diameter with diameter>1.5 mm.The above mentioned results showed that the two valence states of selenium were toxic to the young part of the root system.(4)When the concentration of two kinds of valence selenium was?150mg/kg,it could increase the activity of antioxidant enzymes,chlorophyll content,soluble sugar content and decrease the content of malondialdehyde(MDA);however,at high concentration(?180mg/kg),it decreased the antioxidant enzyme activity,soluble sugar content and chlorophyll content,but increased the MDA content.When the concentration of two kinds of valence selenium was 210mg/kg,the concentration of MDA in the leaves of cardamine was the highes;Treated with 60mg/kg,the concentration of MDA in the leaves reached the lowest value.The results showed that cardamine has a strong stress resistance ability under the selenium stress.