Effect of morphactin on rooting and sprouting of buds on stem cuttings of Salix tetrasperma

Abstract

Morphactin completely inhibits de novo formation of roots on stem cuttings of Salix tetrasperma in spite of continued cambial activity, suggesting its role in preventing differentiation of cambial derivatives into vascular elements. It also prevents the development of preexisting root primordia, except those in which differentiation has reached an advanced stage prior to morphactin application. Very few primordia develop into roots that emerge from nodal regions, and these remain short, their length increasing with a delay in the application of morphactin. Morphactin breaks apical dominance of the root as it does in the shoot, and a large number of secondary roots are produced, concentrated toward the apical end of the primary roots. The secondary roots are sometimes fused together to form hypertrophied structures. Morphactin causes a reversal in the order of sprouting of buds, the lower ones sprouting while the upper ones remain dormant. This is in contrast to the emergence of branches in basipetal order in water-treated control cuttings. These effects are discussed in the light of recent literature on the subject, and it is concluded that the inhibitory effect of morphactin may be ascribed to its antagonism to the effect of endogenous auxin.