ISHS Acta Horticulturae 559: V International Symposium on Protected Cultivation in Mild Winter Climates: Current Trends for Suistainable Technologies
ALTERATION OF GREENHOUSE LIGHT ENVIRONMENT BY PHOTOSELECTIVE COVERS TO PRODUCE COMPACT PLANTS |
| Authors: | N. Rajapakse, T. Cerny, S. Li, R. Oi |
| Keywords: | light quality, spectral filters, plant growth regulation |
| Abstract:
In this paper, we report recent developments in light manipulation as a non-chemical alternative to chemical plant height control of greenhouse crops. Far-red (FR) light absorbing films were effective in reducing height of a wide range of plants, the magnitude varying with species. A dye concentration that gives a light reduction of 25% was found to be suitable for commercial films because films with higher dye concentrations reduced the transmission of photosynthetic photon flux (PPF) but did not result in further height reduction. Among crops tested, watermelon and cucumber seedlings showed more height reduction than bell pepper and tomato seedlings and chrysanthemums. Photoselective films affected the flower development of some crops. Flowering of long day plants (petunia and snapdragon) was delayed by 7 to 13 days under the FR light absorbing film. The films did not affect flowering of miniature roses (day neutral plant), chrysanthemum, zinnia, or cosmos (short day plants). In nature, proportion of FR light increases during early evening. End of the day (EOD) exposure to photoselective films allows growers to make use of high light during the day and exclude elongation-stimulating FR light in the evening. A significant height reduction (25%) could be achieved by EOD exposure to FR light absorbing films (compared to 44% height reduction by continuous exposure). EOD exposed plants had more dry weight than the plant exposed continuously to FR light absorbing films. Depending on height reduction desired, EOD exposure may be solely effective. | |
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