Physiological changes during the senescence process of vegetative propagations of eucalyptus

The young trees of eucalyptus built by different vegetative propagation methods and varied generations were taken as the experimental materials.And their photosynthetic metabolism,nitrogen metabolism,endogenous protected enzyme system,membrane lipid reacting offspring,etc.were tested and compared to explore the rules and differences of variety on eucalyptus senescence with different propagation methods and generations.The results showed that:1) the indices had obvious differences in chlorophyll content,soluble protein content,SOD activity,POD activity,CAT activity,MDA content of different vegetative propagation methods and generations except PRO content.2) According to the research,the testing results showed that with the increase of senescence,the chlorophyll and soluble protein content of leaves decreased;the activity of SOD decreased in the mass and its minimum activity caused by different treatments would appear in different tree ages;the activity of CAT decreased and the activity of POD showed descending trend at first and then ascended;while the content of MDA showed the trend of rising-declining-rising;the content of dissociative proline increased at first and then decreased.3) Chlorophyll content,soluble protein content,SOD activity,POD activity and MDA content could explore the anti-senescence ability of eucalyptus stably and accurately;the five indices above had obvious correlations with the senescence of eucalyptus;chlorophyll content,soluble protein content and SOD activity had positive relationship with the anti-senescence ability of eucalyptus,ie the more the numerical values were,the stronger the anti-senescence ability was; while the POD activity and MDA content had negative relationship with the anti-senescence ability of eucalyptus,ie the more the values were,the weaker the anti-senescence ability was;CAD activity and PRO content were irrelated with the senescence of eucalyptus,thus both of them couldn't be used to evaluate the anti-senescence ability of eucalyptus.4) According to the above testing results by the seven physiological indices,the resistance to senescence of the first tissue culture generation was the strongest,the eighth tissue culture generation was second,and the third generation from cutting was the weakest.It is suggested that the materials of vegetative propagation would be renovated and renewed periodically during production to ensure the reliability and stability of vegetative propagation.