ISHS Acta Horticulturae 541: IV International Symposium on New Floricultural Crops
EFFECTS OF LOW TEMPERATURES AND PHOTOPERIOD ON FLOWERING OF LIMONIUM GMELINII |
| Authors: | E. Farina, C. Dalla Guda, E. Scordo |
| Keywords: | Ornamentals, Cut Flower |
| Abstract:
Limonium gmelinii is a perennial plant flowering in spring-summer. The effect of low temperatures and photoperiod was investigated with the aim to obtain information useful to manage growth and flowering. Different temperature treatments (6; 11; 16; 21 ° C for 5 weeks) were applied to seedlings with 2; 4; 8 true leaves in growth rooms with fixed photoperiod of 12 hours and PPFD of 50 mmol sec-1 m-2 by HPS lamps. After the treatments, the plants were grown in cold greenhouse with 16 h photoperiods and minimum temperature of 16 °C. In no case the plants succeeded in blooming within 87 days (August 5- October 31). In a second experiment, 6 or 24 °C were applied to seedlings with 16-20 true leaves or to adult plants for 5 weeks. The plants were transferred to a greenhouse and grown in ND conditions (August 23-November 30). None of the plants subjected to 24 °C for 5 weeks bloomed independently of growth stage. On the contrary both the adult plants and the plants with more than 16 leaves coming from the low temperature treatment reached flowering. In a third experiment, LD conditions (16 h) enhanced flowering rate of vernalized adult plants. In a further experiment on adult plants a succession of 4 weeks at 6 °C, 4 weeks at 32 °C, 2 weeks at 6 °C was compared with a treatment at 6 °C for 6 weeks. The effect of the exposure to high temperatures was an increase of the flowering rate. In conclusion, a low temperature exposure of the plants in a suitable growth stage is necessary for blooming. LD conditions enhance flowering rate after the fulfilment of the chilling requirement. Five weeks at 6 °C applied to plants with more than 16 leaves are sufficient for flowering. Devernalization was not observed after exposure of the vernalized adult plants to constant 32 °C for 4 weeks. | |
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