| Cleome viscosa L.is an annual plant widely distributed in the tropics and subtropics.It has the characteristics of large biomass,beautiful plant shape,fast growth speed,large seed volume,strong stress resistance,etc.Field investigation found that C.viscosa is the dominant plant in the wasteland of Xiangtan Manganese Mine.It can flower and bear seeds normally in this wasteland of manganese mine.Therefore,this plant has great application potential in phytoremediation of Mn-contaminated soil.In order to reveal the mechanism of the plant’s adaptation to Mn stress,in this study,the mining ecotype(ME)and the non-mining ecotype(NME)C.viscosa were used as research objects.The growth,enrichment ability,the subcellular distribution and the chemical form,physiology and biochemistry characteristics of two ecotypes of C.viscosa on Mn were studied by pot experiments.The results are as follows:(1)The germination of two ecotypes of C.viscosa was inhibited under Mn stress.Under the treatment of 20000 μMn,the germination rate of ME and NME decreased by 30.60%and 81.81%respectively compared with the control.When the Mn treatment concentration is more than 5000 μM,the growth of the two ecotype of C.viscosa seedlings was inhibited,and the degree of inhibition of the NME was greater than ME.(2)With the increase of Mn treatment concentration,the biomass of ME increased first and then decreased,and the biomass of NME continued to decreased.The reproductive allocation and harvest index of the two ecotypes of C.viscosa increased with increasing Mn treatment concentration.The flowering time and seed setting time of the two ecotypes of C.viscosa were advanced under low-concentration Mn treatment,and delayed under high-concentration Mn treatment,and the NME delayed longer,postponed 5-7 days.(3)With increasing Mn treatment concentration,the leaf thickness,epidermis thickness,sponge tissue thickness,palisade tissue thickness,the ratio of palisade tissue to spongy tissue and tissue structure compactness of two ecotypes of C.viscosa were decreased,and the corresponding indicators of ME were significantly higher than that of NME.The stomata size and opening degree of ME in all treatments larger than NME,and the stomata density is smaller than that in NME.(4)The net phyotosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci)and transpiration rate(Tr)of two ecotypes of C.viscosa were decreased with the increasing Mn treatment concentration,and the decrease degree of NME was greater than ME.The Pn,Gs,Ci and Tr of ME reached the maximum value at 1000 μM Mn treatment.(5)With increasing Mn treatment concentration,the value of chlorophyll content and chlorophyll a/b in the seedling stage,mature stage of ME,and in the mature stage of NME increased first and then decreased.Malondialdehyde(MDA)increased with increasing Mn concentration,and the increase degree of NME was greater than ME.(6)The Mn content of two ecotypes of C.viscosa was increased with the increased Mn treatment concentration.Under the treatment of 20000 μM Mn,the Mn content in the leaves of ME can reach 14708.59 mg·kg-1,and the Mn content of NME leaves is 12067.71 mg·kg-1.The content of Mn in cell wall and soluble fractions of two ecotypes of C.viscosa is the largest;in terms of chemical form of Mn,Mn in the two ecotypes of C.viscosa mainly exists in the form of sodium chloride(NaCl)extraction,acetic acid(HAc)extraction and hydrochloric acid(HCl)extraction,and the corresponding extraction form of ME accounts for a larger proportion.This is an important mechanism for two ecotypes of C.viscosa that can enrich a large amount of Mn and reduce the toxicity of Mn. |
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