The Origin and Development of Induced Branches in Helianthus

The development of buds and their vascular connections are described for Helianthus annuus and H. bolanderi. Bud meristems of H. annuus usually become isolated by parenchymatization of the bud traces in the cortical zone. If the buds are induced to grow as a result of decapitation of the terminal meristem, a continuous range between typical primary connections and pseudo-adventitious connections are made between the main axis and the lateral buds. Considerable growth of the branches occurs within 48 hours after decapitation. Axillary buds of H. bolanderi grow continuously, and both the meristem and vascular system of the buds are derived directly from the apical meristem of the shoots.