Regeneration Around Wounds and the Control of Vascular Differentiation

The question which was the basis of this work was whether (a)vascular regeneration around wounds includes a replacement ofdamaged tissues or (b) only new vascular strands, which arenormally formed from the cambium, are diverted around wounds.It was found that in Coleus and Cucumis no connections are formedto damaged sieve tubes and vessels, so that their continuityaround wounds is not restored. Pisum plants were wounded underconditions in which growth could not be influenced and the areaof the xylem in cross-section was measured 1 month later. Thewounds, which damaged the vascular tissues, significantly increasedvascular differentiation, indicating the replacement of a longnon-functional region of damaged tissues. The results indicatethat in the intact plant vascular differentiation is controllednot only by stimuli from the leaves but also by the capacityof the mature vascular system to transport these stimuli.