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| Improving growth by extending day-length | |
| By applying long-days to various ornamental crops, especially in winter and early spring when days are naturally short and light levels low, plant growth can benefit. Experiments with young plants (plugs) of Anthurium, Begonia, Pelargonium, Impatiens, Viola and Petunia showed that long-day lighting reduced cropping time by an average of about 6% against 20% for supplementary lighting. Long-day lighting is much much cheaper than supplementary lighting. Lighting to extend the day to 16 hours was more successful than 2 hours of night-break lighting. The light level applied was about 3µmol/mq/s (0.6W/mqPAR) which equates to about 150 lux from tungsten lamps, 225 lux from fluorescent lamps and 245 lux from high pressure sodium lamps. Under long day lighting, Petunia showed an increase of 20-100% in above ground dry weight, more marked when daytime light levels were low. Under these conditions, plants produced larger, thinner leaves. These were less efficient under high light conditions, more than compensated by photostynthetic efficiency when light levels were low. In Impatiens, there was a 30-40% increase in dry weight as a result of long- day light but no apparent increase in the thickness of the leaves. Long-day lighting can enhance growth and increase crop productivity during winter and early spring. The technique is of no value to plants that require short days to flower. Steve Adams and Allen Langton “Grower” HRI (Horticulture Research Institute), University of Warwick. Fax 0044 2476574500 E-mail: steven.adams@warwick.ac.uk www.warwickhri.ac.uk |
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