INFLUENCE OF LIGHT AND TEMPERATURE ON FLOWER-BUD DEVELOPMENT IN BULBOUS IRISES (IRIS CV. 'WEDGWOOD') AND LILIES (LILIUM CV. 'ENCHANTMENT')
For Iris 'Wedgwood' the percentage of blasted flowers is considerably higher at air temperatures above 15 or 18°C. The minimal requirement of light (fluorescent) for normal development at 15°C is about 30 cal cm-2day-1, but this value increases sharply at higher temperatures. The results indicate that between 15 and 24°C, the higher the temperature, the higher the minimum light intensity that ensures normal flower-bud development. A photoperiodic long-day effect does not seem to be involved.
Preliminary experiments on the development of flowers buds of Lilium 'Enchantment' showed that light is more critical than temperature: between 15 and 24°C, higher temperatures gave relatively low extra losses due to stagnation of flower-bud development. In the experiments with fluorescent light (phytotron Wageningen) a minimum amount of about 30 cal cm-2day-1 was required to prevent bud blasting and about 60 cal cm-2day-1 to prevent flower-bud abscission. It is still uncertain whether the amount of light (energy effect) or the photoperiod (or both) is decisive in this respect.
The following findings suggest that in lilies, bud blasting and bud abscission may be more or less independent physiological phenomena:
- Bud abscission started in the lowest flowers, whereas bud blasting started in the top flowers.
- The amount of light required to prevent bud blasting was lower than that needed to prevent bud abscission.
- Higher air temperature tended to decrease bud abscission and to increase bud blasting.
- The period in which bud abscission occurred did not coincide with that of bud blasting.