Research On Browning Mechanism And Factors Influencing The Explant Browning In Preliminary Culture In Vitro Of Peony

Tissue oxidative browning is a key factor,that of interfered with normal propagation of peony tissue culture. This paper , the mechanism of tissue oxidative the explant browning of peony explant and factors influencing the explant browning in preliminary culture in vitro of peony were studies The browning index PPO activity, content of total phenolic contents activities of SOD POD and CAT, MDA level and membrane relative permeability were measured on 1, 3 ,5, 7 ,11 ,15 days, respectively. The relationship between these traits and the browning were analyzed .The results showed that: the brown index reached 90% after 15 days culture .During the culture days ,the content of total phenolic contents first increased by composing and then decreased by decomposing. Activities of PPO, POD were increased remarkably in prophase while increased in anaphase .Activities of SOD, CAT were decreased during the culture days. MDA level and membrane relative permeability increased sharply. Analyzing correlation reveals that the correlation relationship of total phenol content and brown index is significant. Total phenolic content can deteriorate the degree of browning . Huhong ,which has higher total phenol content happens browning more easily.On the other hand during of the period of PPO activity reached its peak, content of total phenolic contents is decreasing. So the explant browning of peony was due to that the total phenol contents was catalyzed by PPO while oxygen existed. Because that both PPO activities and total phenol content positively related with brown index in prophase while negatively related in anaphase,that is to say ,there are two phases during the explant browning.one phase is a switch on browning,phase that another is that the browning change into intensively.The results of correlation analysis of membrane system suggested that thebrowning could result in the changes of superoxidation and phases of the membrane of the cell membrane system. Further more ,the compartment of polyphenols and PPO can be destroyed and the browning of the explant developed. Hence it is the main reason causeing explant browning to change into intensively at the later stage that the test is think that membrane seepage adds 。Factors influencing the explant browning in preliminary culture in vitro of peony were studies. The results showed that the position and date of picking the shoots of peony are the key factors,which of effecting on the browning of the peony. Picking shoots in the middle of April appeared to be optimum for reducing browning rate and improving survival of the explants. The terminal bud is better than axillary bud for its lower browning rate .Culturing at low temperature is necessary condition for avoiding browning .Yet low temperature handle can cut down the body viability. Powerful light is provoking the activitie of PPO, piece be culture in the powerful light happens browning more easily . Moreover test is confirmed that more macro-element medium and using hormone at high level could increase the degree of browning. Add VC, active carbon, PVP and sodium hyposulfite cannot overcome the browning of shoots of peony...