Studies On The Effects And Mechanism Of Adventitious Root Formation Promoted By LFS

It is generally believed that IAA is the main hormone to promote adventitious roots,while cytokinins(CTK),such as 6-BA,KT and ZT,will suppress adventitious root formation.LFS,a new hormorne,belongs to CTK according to its chemical constitution and bioactivity.However,we found that LFS could promote the adventitious root,which has similar function with IAA but reverse function to the other CTKs.Fourplant species,namely Mung bean,Cucumber,Fructus Momordicae and Arabidopsis thaliana were used as study materials to identify the effects of LFS on adventitious root formation. Besides,studies on the biological effects,form anatomy,enzyme activity and entogenous hormone were conducted so as to prone into the mechanism of adventitious root formation promoted by LFS.The main results were summarized as follows:1.The treatment with LFS could promote the rooting rate,root number and rooting scope of the tissue-culture plantlets of Fructus Momordicae and Arabidopsis thaliana.The similar results were obtained in rooting experiments of the Mung bean hypocotyls and Cucumber stump plants. Concentration and time effects of LFS on the adventitious root formation were obvious.The treatment with the LFS concentration of 10^-5mol·L^-1acted best when compared to other treatments with the concentration range from 10^-6mol.L^-1to 10^-3mol·L^-1.Best results could be obtained by continuous LFS treatment for more than 24h,or LFS treatment after 12～24h of the stump plants were exsomatized from the stock plants.2.The adventitious root primordia of Mung bean hypocotyl were generated 48～72h after the stump plants were exsomatized from the stock plants,which were differentiated from the parenchymatous cells between vascular tissue.The location of adventitious-root primordia under LFS treatment was similar with that under the control(CK).However,the development of adventitious-root primordia under LFS treatment grew faster than that under CK.The formation of adventitious root could be divided into 5 stages as followings:0～12h,differentiation stage;12～24h,induction stage; 24～48h,cell division stage;48～72h,the stage for the formation of root primordia;72～96h,the stage for the growth of root primordia and formation of adventitious-root.3.IAAO,POD and PPO were three major enzymes which could regulate the content of entogenous IAA so as to affect the occurrence and development of plants' adventitious root inderectly.During t he formation of adventitious roots,LFS treatments could reduce the activity of IAAO,but promote the activity of POD and PPO. 4.The results of entogenous hormone's identification indicated that the LFS treatment could promote the contents of entogenous IAA and ABA but reduce the content of GA,while it showed no abvious effects on the content of ZR;LFS treatment had similar effects on the content of entogenous IAA, ZR and ABA as IBA,i.e.the ratio of IAA/ZR and IAA/ABA reached the peak value in 48h(earlier stage of the formation of adventitious root primordia) and 96h(stage for the formation of adventitious root),respectively.In conclusion,the effect of LFS on the formation of adventitious root was closely-related to the level of entogenous IAA.At different stage of the adventitious root formation,LFS could regulate the activities of IAAO,POD and PPO,then indirectly affected the metabolism of IAA,which would promote the content of IAA in stump plants;meanwhile,LFS could also regulate the contents of ZR and ABA in stump plants.Therefore,the ratio of IAA/ZR reached high level before the formation of adventitious root primordia,and the ratio of IAA/ABA reached high level too during the formation of adventitious root,which would promote the formation of adventitious root.