The effect of cambial zone isolation upon the autolytic system in maturing tracheids of pine (Pinus silvestris L.)

Abstract

The autolytic protease system in maturing tracheids of the main stem of Pinus silvestris was investigated after separation (using surgical methods) of the cambial zone from the layer of differentiating xylem, in combination with decapitation and IAA application. Separation of the cambium prevented autolysis of the protoplast in maturing tracheids, although the specific activity of proteases was little reduced. It was found that a radial or longitudinal concentration gradient of exogenously applied auxin was not responsible for autolysis, but that it could influence the level of extracted protein, and proteolytic activity. Similarly, decapitation modified, only to small degree, the effects of the cambium separation. Thus, the data from this experiment lead to the conclusion that integration of all cells in the region of xylem formation is a crucial factor for the start of autolytic protoplast breakdown. Possible involvement of auxin waves in the transfer of the positional information for this process is suggested.