| Populus euphratica Oliver is a rare but important natural forest tree species in the hinterlands of the deserts of central Asia,including China,with conditions of salinity,drought,cold,wind resistance and other characteristics of arid regions.It has a role play in conserve and regulation drought and desertification and help in keeping a fragile ecological balance in these regions,and as well improvement the ecological environment of oasis agriculture.As a result of the limit of sexual reproduction in a large-scale and easy separation of the genetic traits,the vegetative propagation became an important means of propagation.However,it is difficult for P.euphratica to induce roots from cuttings for propagation and become the bottleneck of industrial development of P.euphratica, need to be solved.Using the adventitious root formation(ARF) regulation system,and microscopy, gas chromatography-mass spectrometry(GC-MS) and cDNA cloning techniques in the cellular and molecular levels,our study describes a variation of cell,organization structure and several physiological and biochemical indicators such as hormones and isozyme during the process of the adventitious roots occurrence.Analysis the biological information of the difference cDNA clones. The research results will be the important basic works of identifying the molecular mechanism of adventitious root occurrence and developmen in-depth,and realizaed of human control of adventitious roots occurred.It has an important theoretical and practical significance for germplasm conservation and genetic improvement.The results are as follows:1.Rapid Propagation system of P.euphratica,were the first time establishment with inflorescence explants.The optimal medium for callus induction of male and female inflorescence on a B5 medium, containing 1.0 mg·L-1 6-BA and 0.5mg·L-1 NAA for female inflorescence or containing 1.0 mg·L-1 6-BA and 1.0mg·L-1 NAA for male inflorescence,has an induction rate of 98.0%,which includes over 63%green calli with an affinity for a bud regeneration of both male and female inflorescence.The optimal medium for callus subculture were that in the B5 medium add 1.0 mg·L-1 6-BA and 1.25mg·L-1 NAA or MS medium add 1.0 mg·L-1 6-BA and 0.5mg·L-1 NAA.A bud induction on a MS medium,containing 0.5 mg·L-1 6-BA and 0.2 mg·L-1 NAA,has an induction rate of 31.2%.A LS medium containing 1.0 mg·L-1 6-BA and 0.5 mg·L-1 NAA has an induction rate of 33.3%,where the appropriate 6-BA/NAA ratio lies between 2.0 and 2.5.The optimal medium for rooting on a 1/2 MS medium,containing 0.5 mg·L-1 IBA,has an induction rate of at least 35.0%.The seedlings propagation period of P.euphratica using inflorescence explants in vitro is shorter than the other explants nearly two weeks.2.In addition to the establishment of a callus of P.euphratica than seedlings stem cuttings and buds induction adventitious root occurred in regulation system can be used to study the occurrence and ARF as a good experimental system.The micro-and ultrastructural features of adventitious roots formation and development from seedlings stem cuttings were observed in detail.The stem cuttings in medium without IBA,has major nuclear cells around the vascular at 36 h.More aleurone grains accumulated in these cells and which distribute relative concentration at 48 h;Adventitious root primordial,formed vascular bundle,were original from vascular cambium and phloem organizations and pith ray at 60 h.The adventitious root formation was at 72 h,and meanwhile the nuclear membrane integrity,nuclear major,and mostly nuclear with ring nucleoli.The root primordia formation of stem cuttings in medium with 0.5 mg·L-1 IBA were completely inhibited,and dedifferentiation organizations induced callus at the base of stem cuttings.3.The variation of hormone associated with occurrence of adventitious roots was more accurate analysis by using GC-MS technique.During the process of ARF,we noted that endogenous hormones IAA and ABA have an important role play in induced root primordium as an important signaling molecule.If the IAA concentration in particularly a certain extent and in a relatively stable state,that will promote the occurrence of adventitious roots.If the IAA concentration above a certain threshold and unstable,inhibit the occurrence of adventitious roots.Additional,the ratio between IAA and other hormones,such as GA3 and ABA,etc.also affect the occurrence of adventitious roots.Endogenous hormone GA3 status in a more stable and is conducive to the formation of adventitious roots. 4.Polyacrylamide gel electrophoresis(PAGE) was used to detect the action of peroxidase(POD). The 2 b bands of POD continued expression related to the adventitious root primordium induction,it may be promotion IBAβ-oxidation and activated the IAA which inhibition of root growth,to achieve the effective concentration threshold of rooting.The amylase expression increase and be as a sign of root primordium development at 60 h.It does not in activation of esterase during root primordium induction,and does in activation during root primordia development.5.The different expression cDNA clones of female inflorescence callus response to the IBA signal during induced adventitious root were investigated by rapid cloning technology of Gene FishingTM and a preliminary analysis of the data.The cDNA clone,No.0-5,from the callus cultured in medium which without IBA,maybe encode leucine-rich repeat domain protein and participation the signal transduction-related with root inhibition processes;The clone of No.0-4,its protein sequences partly similar to the hydrolase,which maybe inhibit the primordium formation of adventitious root.The clone,No.1-34-1,from the callus cultured in medium with IBA,maybe encode epidermal protein 140 (RR-2 family) and involved in the process of ARF.6.Comparison of different types of stem cutting in rooting induced and analysis the cDNA clones which may be associated with the occurrence of adventitious roots of P.euphratica,the model of ARF were initial establishment of exogenous IBA controlling endogenous IAA occurred threshold and equilibrium,that is,exogenous IBA receiving by receptor of stem cutting,and transfer into the cells,then turn into active IAA by the effects of the POD enzyme.While the endogenous IAA concentration were in the range of rooting threshold value and remained relatively stable,it enhanced the ARF.However,while the IAA concentration were above the threshold and do not stability,it inhibited the ARF.
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