ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture
LIGHT QUALITY REQUIREMENTS IN LATITUDINAL POPULATIONS OF NORWAY SPRUCE |
| Authors: | J.A. Molmann, O. Junttila, O. Johnsen, J.E. Olsen |
| Keywords: | climatic adaptation, provenances, spectral irradiance, Picea abies |
| Abstract:
Seedlings of trees with a free growth pattern cease growth in night lengths shorter than a critical value. The critical night length decreases with increasing latitude of origin. The light quality also appears to play an important role and a clinal variation in requirement for far-red (FR) light has been documented. However, these studies used broad-spectrum light sources enriched in certain wavelength areas, covering also large ranges of wavelengths outside the activity maxima of phytochromes or cryptochromes. Recently, we performed studies in which we dissected the light quality requirements for maintaining growth in different latitudinal populations of Norway spruce using precisely defined wavelengths from light emitting diodes for red (R), far red (FR) or blue (B) light, as day extensions. At equal spectral photon flux, FR was more effective than R light in maintaining growth, but the requirement of both R and FR increased with northern latitude of origin. One-to-one mixtures of R and FR light were more effective maintaining growth than either FR or R light alone, suggesting the involvement of more than one species of phytochrome. B light as day extension did not prevent growth cessation, but delayed the bud set in all populations. Our results suggest that multiple phytochromes, or different photoisomers of one phytochrome, are the primary photoreceptors in high irradiance responses maintaining growth in Norway spruce seedlings. | |
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