ISHS Acta Horticulturae 545: V International Protea Research Symposium
MATURE OVERWINTERING LEAVES ARE ESSENTIAL FOR INFLORESCENCE INITIATION AND DEVELOPMENT IN PROTEA CVS. CARNIVAL AND LADY DI |
| Authors: | A.I. Gerber, K.I. Theron, G. Jacobs |
| Keywords: | Proteaceae, defoliation, induction, source strength, delayed flowering |
| Abstract:
Both Protea cv. Carnival and Protea cv. Lady Di produce inflorescences subtended by the spring growth flush on an overwintering shoot. Inflorescence initiation starts at spring budbreak, and production of involucral bracts occurs concurrently with spring flush elongation. Inflorescence development continues after elongation of the spring flush is complete, and inflorescence growth occurs through summer. Defoliation trials indicated that shoots of ‘Carnival’ were in the induced state and committed to flowering 6-7 weeks before spring budbreak. Total defoliation applied before the induced state was achieved prevented inflorescence initiation, indicating that mature overwintering leaves must be retained for a period of time for successful inflorescence initiation to occur. Growth and development of the ‘Carnival’ inflorescence, however, is supported by the spring flush. Defoliation treatments which resulted in a weak spring flush retarded inflorescence development and lead to later anthesis. Defoliation treatments applied after completion of spring flush elongation had no effect on either vegetative or reproductive spring growth. In ‘Lady Di’ mature overwintering leaves are essential for shoots to achieve the induced state for flowering, and are also crucial to the early stages of inflorescence initiation. Defoliation applied to shoots before formation of involucral bracts was complete prevented flowering. Defoliated shoots either remained vegetative or produced inflorescences which aborted. Defoliation treatments that did not prevent inflorescence initiation, had no effect on inflorescence development, and flowering time of 'Lady Di' was not delayed by defoliation. The requirement for mature overwintering leaves to effect inflorescence initiation in ‘Carnival’ and ‘Lady Di’ suggests that environmental factors, such as low temperature and daylength may play an inductive role. | |
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