Manipulation of bolting and flowering in celery (Apium graveolensL. var.dulce). II. Juvenility

SummaryAfter germination, a juvenile phase of development was apparent in cvs New Dwarf White and Celebrity. During this incompetent phase, plants were not induced flower even when subjected to chilling at 5°C for nine weeks. Juvenility ended and the plants became competent to perceive chilling as a vernalization stimulus when they had initiated 17 leaves including leaf primordia in cv. New Dwarf White and between 17 and 20 leaves in cv. Celebrity. After phase transition, the level of competence was not affected by plant age. The rate of leaf initiation in cv. New Dwarf White during juvenile and competent vegetative growth related linearly to temperature, increasing between 3 and 22.8°C and then declining over the range 22.8 to 37.4°C. The first 17 leaves of celery cv. New Dwarf White had longer plastochrons of 43° Cd (>3°C) each than subsequently initiated leaves with 29° Cd for each leaf. The thermal time requirement for completion of juvenile development after radicle emergence was 731° Cd> 3°C. In cv. Celebrity the first 17 leaves required 42° Cd each for initiation.