STIMULATION OF CAMBIAL ACTIVITY, LOCALLY IN THE REGION OF APPLICATION AND AT A DISTANCE IN RELATION TO A WOUND, BY MEANS OF HETEROAUXIN

Abstract

The application of heteroauxin in lanoline (1 mg. of heteroauxin per gm. of lanoline) to the distal end of disbudded cuttings of leader shoots of balsam poplar, stimulated cambial activity for a distance of 1.0–1.5 in. below the point of application. Marked stimulation of local cambial activity, in relation to a bridged ring some considerable distance below the point of application of the heteroauxin, was also obtained. The response at the wound was distinct and separate from the response in the region of application of the heteroauxin, since in the intervening distance no cambial activity had occurred. The experiments were carried out during the winter months, so that the cambium was dormant in material as it came from the field. Cambial activity subsequent to treatment was estimated in terms of xylem formation. The structural features of this new xylem are described and discussed, with particular reference to the question as to whether heteroauxin stimulates cell division only in the cambium or, in addition, is active in differentiation of typical xylem elements.