Effects Of Indole Acetic Acid And Kinetin With Combined Application On Arsenic Uptake And Physiological And Biochemical Properties By Pteris Vittata

Exogenous application of plant hormones can effectively promote plant growth and metal uptake,but the related mechanisms are not fully understood.The objective of this study was to examine the effects of the combination usage of indole acetic acid?IAA?and kinetin?KT?to improve arsenic?As?uptake and the physiological and biochemical properties in As hyperaccumulator Pteris vittata.Firstly,the orthogonal pot experiments were designed as 2 factors and 4 levels using the soil containing 55mg·kg^-11 As.IAA(0,25,50,100 mg·L^-1)and KT(0,20,40,60 mg·L^-1)were foliar-applied,and the optimized plant hormones combination dosage to achieve the highest As extraction efficiency by P.vittata was identified.Secondly,P.vittata was planted in soil with the same As content,and the effects of four treatments,namely without hormone?CK?,individual hormone?IAA or KT?,and the optimized hormone combination?IAA+KT?,on physiological and biochemical characteristics of plant were investigated.Additionally,the time-course effect of each physiological and biochemical index under the optimized hormone combination condition was also performed,including biomass,root morphology,root activity,photosynthetic pigment content,leaf osmotic adjustment substance content and As contents in different parts of P.vittata.Therefore,the related physiological and biochemical mechanisms under the optimized hormone combination condition were further explored.Lastly,P.vittata was planted in two types of contaminated soils,paddy soil and red soil,which were collected in the field.Four-treatment experiment of plant hormone and time-course effect under the optimized hormone combination condition were performed.Furthermore,the effects of the optimized hormone combination on As,Cd and Pb uptake by P.vittata and their bioavailability in soil were also investigated.The results showed as follows:1.The combined application of IAA and KT effectively promoted the rapid growth of P.vittata,and significantly increased the As extraction efficiency.After two months of planting,the combined application of 25 mg·L^-11 IAA and 20 mg·L^-11 KT resulted in the highest As extraction efficiency of P.vittata among 16 kinds of hormone combinations,up to 6.49%,which was 4.7 times higher than CK.2.Compared to CK and individual hormone treatments,the root morphology of P.vittata was effectively improved,and plant height,dry weight,root activity,chlorophyll b content,and peroxidase?POD?activity were significantly increased with IAA and KT combined application after one-month planting.The time-course effect experiment showed that under the optimized hormone combination condition,plant height,dry weight,root activity,photosynthetic pigment,proline and soluble sugar contents of P.vittata were significantly increased compared to CK.Correlation analysis demonstrated the best As extraction efficiency of P.vittata due to the combined application of 25 mg·L^-11 IAA and 20 mg·L^-11 KT was attribute to the foliar-applied plant hormones significantly improved the P.vittata aboveground dry weight,root length,root activity,chlorophyll a,chlorophyll b and carotenoid contents and frond POD activity.Therefore,keeping a high aboveground biomass,root activity,photosynthetic pigment content,and POD activity in P.vittata contributed to the promotion of its As extraction efficiency.3.In As,Cd,Pb co-contaminated paddy soil and As,Cd co-contaminated red soil,As content in aboveground part,Cd and Pb contents in underground part of P.vittata were significantly increased with IAA and KT combined application.After 60days of planting,the contents of total As,Cd and Pb in soil were significantly decreased.The total contents of As,Cd,and Pb in paddy soil were decreased by22.5%,17.1%and 5.1%,and the total contents of As and Cd in red soil were decreased by 3.9%and 12.0%,respectively.The time-course effect experiment showed that the bioavailable As and Cd contents in paddy soil showed a decreasing trend,and the bioavailable Pb content was decreased first and then increased;whereas the bioavailable As content in red soil was decreased first and then increased,and the available Cd content was irregularly changed.These results indicated that exogenous application of IAA and KT could promote the uptake of heavy metals in plant and reduce the heavy metals contents in soil.At the same time,the effects of IAA and KT on the bioavailability of heavy metals in contaminated soils varied,due to different soil types and different heavy metal contents in soil.