POLARITY OF TRACHEARY REGENERATION IN YOUNG INTERNODES OF COLEUS (LABIATAE)

After Jacobs’ recent discovery of almost absolute basipetal polarity of IAA-¹⁴C movement through young internodes of Coleus, tracheary regeneration around a wound in the stem was re-investigated to see if it showed parallel changes from the less strict polarity of IAA-¹⁴C described decades ago. As determined from either counts of “complete regenerated strands” or from finer details of regeneration, tracheary regeneration was very strongly polar. If leaves were present only below the wound, no regenerated strands developed unless there was a sizeable length of leafless stem remaining above the wound. If there were leaves below the wound as well as above it the amount of regeneration was usually reduced. The short strands of acropetally regenerating tracheary cells, previously interpreted as resulting from acropetal IAA movement, were observed in plants with leaves above but not below the wound, and were not seen in plants with leaves only below the wound. Hence, they are more likely to result from basipetally moving IAA. Isolated patches of tracheary regeneration were observed under several conditions. The wound interfered with development of the leaf directly above the wound.