ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture
USING LIMITED INDUCTIVE PHOTOPERIOD FOR SCHEDULING COSMOS BIPINNATUS AND TAGETES TENUIFOLIA |
| Author: | R.M. Warner |
| Keywords: | photoperiodism, flower induction, crop timing, juvenility |
| Abstract:
The understanding that many bedding plant species flower in response to photoperiod has allowed more precise control of flowering. However, for most crops there is very little information on when plants are receptive to photoperiodic promotion of flowering (i.e. how many leaves must a plant unfold before it is capable of being induced to flower) or how many photoinductive cycles are necessary for floral induction. The work presented here aims to determine the length of the juvenile phase and the number of photoinductive cycles necessary to induce flowering of Cosmos bipinnatus ‘Sonata White’ and Tagetes tenuifolia ‘Tangerine Gem’, both previously identified as short-day plants. All plants were grown at constant 20ºC. C. bipinnatus ‘Sonata White’, and T. tenuifolia ‘Tangerine Gem’ were grown under a non-photoinductive long-day environment [9-h photoperiod plus night-interruption (2 µmol m-2 s-1 provided by incandescent lamps from 2200-0200 HR)], before being transferred to a photoinductive short-day environment (9-h photoperiod) 0, 5, 10, 15, 20, or 25 d after the first true leaf pair unfolded. Plants were grown under short days for 5, 10, 15, 20, 25 or 30 d, and then moved back to long days. Control plant groups were maintained under short days or long days for the duration of the experiment. As few as five short days were sufficient to hasten flowering of both C. bipinnatus and T. tenuifolia, even for seedlings with only one leaf pair unfolded. For both species, increasing the number of short days increased flower bud number. | |
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