A COMPARATIVE DEVELOPMENTAL STUDY OF THE MUTANT SIDESHOOTLESS AND NORMAL TOMATO PLANTS

'Sideshootless,’ a mutant strain of tomato which does not produce axillary buds during vegetative growth, was compared with normally branching plants in order to study the nature of development particularly with regard to axillary buds. Sectioned material revealed no indication of axillary bud initiation in the sideshootless plant at any time during the vegetative phase of growth. In the normal plants, buds were noted to arise in the axil of the fifth youngest leaf. The buds take their origin in tissue which is in direct continuity with the apical meristem. The bud primordia later become set apart from the apex as vacuolation takes place in the surrounding tissue. At the time of floral initiation, the mutant and normal strains behave similarly. Axillary buds appear in the axils of the 2 leaves immediately below the floral apex. One of the buds elongates to overtop the existing plant axis; the other develops as a typical sidebranch. The inflorescence is pushed aside in the process. This pattern is repeated with each inflorescence; thus an axis composed of several superimposed laterals results.