PROTEOLYTIC ACTIVITY IN THE STEM CAMBIAL REGION OF PINUS-SYLVESTRIS L- A CONTRIBUTION TO THE SPECIFIC DIFFERENTIATION OF SECONDARY XYLEM AND PHLOEM

Proteolytic activity was studied in the differentiating xylem and phlo em of Scots pine (Pinus sylvestris L.) to determine the specificity of xylem and phloem differentiation. The activity of autolytic proteases was demonstrated in the differentiating xylem during spring, summer a nd autumn and it was not detectable during winter. It was initiated wi th the onset of cambial activity in spring and unchanged during subseq uent stages of xylem differentiation. The same proteolytic activity wa s not detectable in the extract of fresh phloem tissue. It could be de tected in phloem after removal of the inhibitor found in the extract. The same pH optimum was determined for proteases extracted from xylem and phloem. However, their identity remains uncertain because of diffe rent electrophoretic mobility. On the other hand the presence of prote ase inhibitor in phloem tissue can be an important factor im determini ng the specificity of xylem an phloem differentiation.