JUVENILITY AND PHOTOPERIODIC FLOWERING REQUIREMENTS OF CHRYSANTHEMUM X SUPERBUM G-MARCONI AND SNOW-LADY GROWN UNDER SHORT-DAY AND LONG-DAY CONDITIONS

Juvenility and flowering requirements of Chrysanthemum xsuperbum Bergmans ex J. Ingram 'G. Marconi' and 'Snow Lady' were examined by growing plants under short days (SDs) and transferring them to long days (LDs) upon reaching specific true leaf stages. 'G. Marconi' plants did not flower in continuous SDs and only sparse flowering occurred in plants transferred to LDs. 'Snow Lady' plants transferred from SDs to LDs at the cotyledon stage flowered fastest from seeding (75 days) and had the fewest number of main stem leaves and total leaves (9 and 15, respectively) at the time of first flower. Plants moved from SDs to LDs at the 24 true leaf stage flowered 123 days after seeding and averaged 28 leaves on the main stem and 37 total leaves at the time of first flower. To examine apical floral initiation, plants were distributed between SDs and LDs following transplanting and five plants per treatment were sampled each week thereafter. Microscopic examination revealed floral initiation in plants sampled after just 1 week in LDs and, after 5 weeks, macroscopic terminal flower buds were present. Under SDs, apical floral initiation began after 5 weeks, yet, 9 weeks were required for floral initiation in all five plants sampled.