Study On Endogenous Polyamines Metabolism And Some Related Physio-biochemical Indexes During Dormant Period In Pear Rootstocks

Deciduous fruit trees evolved into biomechanism of dormancy for a long time to adapt to the environmental and climatical changes in winter. This experiment was carried out from 2005 to 2007 in Yangzhou University with pear rootstocks P.pseudopashia,P.betulaefolia,P.calleryana as experimental materials. The chilling requirements in different test materials were investigated, and the contents and kinds of endogenous polyamines in the buds and roots of different test materials during dormancy and growth periods were analyzed. Also the effect of 20%CaCN2 and 2%H2CN2 which are usually used as breaking dormancy chemicals were studied on the sprouting rate and the changes of endogenous polyamines in the buds of pear rootstock P.calleryana. In the same time, the content changes of endogenous hormone GA3,Proline and the activity of PAL in the buds of pear rootstock P.calleryana during dormant period were analyzed. The main results were as follows:1. Chilling requirements (CR) of pear rootstocks were studied, the results showed that P.calleryana CR was the lowest, P.pseudopashia CR was the highest. On evaluation of Chilling requirements(CR), 0-7.2℃model and Utah model were relatively similar.2. Putrescine, spermidine and spermine, three kinds of endogenous polyamines were detected in the buds of test materials, the contents of free polyamines were higher than that of bound polyamines, and the contents of free putrescine and spermidine increased significantly as the chilling requirements were satisfied, it seemed that the content changes of free and bound putrescine and spermidine could be used as an index of physiological metabolism for estimating dormancy depth of buds of pear rootstocks.3. Putrescine, spermidine and spermine, three kinds of endogenous polyamines were detected in the roots of pear rootstocks during the growth and dormant periods. The contents of polyamines on roots of pear rootstocks were significantly lower than that on buds, there are 2 to 3 peaks on the contents of polyamines of roots during the whole year. It could be seen that that the contents of polyamines had great influence on the growth of roots.4. The dormancy of buds in pear rootstock P.calleryana could not only be broken, but also the contents of the free and bound polyamines could be raised in buds and roots by treating branches with 20%CaCN2 and 2%H2CN2 chemicals. And the contents of bound spermidine increased significantly in the roots when using the breaking dormancy chemical 2%H2CN2. The sprouting rates were higher in potted plants than that in vitro. It could be presumed that the dormant depth changes of buds were related to polyamine metabolism in the buds and roots of P.calleryana5. The contents of Gibberellin acid (GA3),proline and the activity of PAL increased significantly as the chilling requirements were satisfied.