UV-B and PAR in single and mixed canopies grown under different UV-B exclusions in the field
- 84 Downloads
The purpose of this study was to investigate whether differences in canopy architecture due to the investigated species (planophile versus erectophile, single versus mixed canopies) or to UV-B effects on plant morphology, lead to differences in UV-B and UV-B/PAR doses within canopies.
The development of a very small (10 mm diameter) UV-B and PAR sensor on a long 5 mm wide stick allowed us to measure the penetration of UV-B and PAR in single and mixed canopies of the grass Dactylis glomerata and white clover, Trifolium repens. The plants were grown in greenhouses covered with different thicknesses (3 and 5 mm) of UV-transmittant plexi (12 and 18% UV-B exclusion).
For clover, a planophile vegetation, radiation penetration was very low for both UV-B and PAR. UV-B penetration was much less than for PAR, resulting in low UV-B/PAR ratio's within the canopy. This is explained by the low UV-B transmittance of the leaves (<0.1 %) in combination with the planophile leaves.
In the grass species, both UV-B and PAR penetrated much deeper into the canopy due to the erectophile structure. The difference between UV-B and PAR penetration was generally quite small except in very tall canopies.
The mixed species canopies showed results comparable to the clover canopies. Due to the strongly increased grass growth in these plots, light penetration was generally much lower than in the single species cultures. The increased growth of grass in these mixed plots could be linked to the lower UV-B/PAR dose they received.
In plots grown under the higher UV-B level there was a relative decrease in UV-B/PAR ratio within the canopy for both species, compared to canopies from the lower UV-B greenhouses. This could not be explained by changes in leaf angle or biomass, but might be linked to the increase in leaf transmittance of PAR.
Unable to display preview. Download preview PDF.
- Allen, L. H., Gausman, H.W. & Allen, W. A. 1975. Solar ultraviolet radiation in terrestrial plant communities. J. Environ. Qual. 4: 285–294.Google Scholar
- Anisimov, O. & Fukshansky, L. 1993. Light-vegetation interaction: a new stochastic approach for description and classification. Agric. Forest Meteorol. 66: 93–110.Google Scholar
- Barnes, P. W., Ballaré, C. L. & Caldwell, M. M. 1996. Photomorphogenic effects of UV-B radiation on plants: consequences for light competition. J. Plant Physiol. 148: 15–20.Google Scholar
- Caldwell, M. M. 1971.Solar ultraviolet radiation and the growth and development of higher plants. Pp. 131–177. In: Giese, A.C. (ed.), Photophysiology, Vol. 6, Academic Press, New York.Google Scholar
- Caldwell, M. M. 1981. Plant response to solar ultraviolet-B radiation. Pp. 170–186. In: Lange, O. L., Nobel, P. S., Osmond, S. B. & Ziegler, H. (eds), Physiological Plant Ecology 12A. Springer-Verlag, Berlin.Google Scholar
- Caldwell, M. M., Flint, S. D. & Searles, P. S. 1994. Spectral balance and UV-B sensitivity of soybean: a field experiment. Plant, Cell Environ. 17: 267–276.Google Scholar
- Caldwell, M. M. 1998. Effects of increased solar ultraviolet radiation on terrestrial ecosystems. J. Photochem. Photobiol. 46: 40–52.Google Scholar
- Cen, Y. P. & Bornman, J. F. 1990. The response of bean plants to UV-B radiation under different irradiances of background visible light. J. Exp. Bot. 41: 1489–1495.Google Scholar
- Day, T. A. 1993. Relating UV-B screening effectiveness to absorbing-compound concentration and anatomical characteristics in a diverse group of plants. Oecologia 95: 542–550.Google Scholar
- Deckmyn G. & Impens I. 1998. UV-B and PAR in a grass (Lolium perenne L.) canopy. Plant Ecol. 137: 13–19.Google Scholar
- Deckmyn G. & Impens I. 1999. Seasonal responses of six poaceae to differential levels of solar UV-B radiation. Environ. Exp. Bot. 41: 177–184.Google Scholar
- Deckmyn, G., Martens, M. & Impens I. 1994. The importance of the ratio UV-B photosynthetic active radiation (PAR) during leaf development as determining factor of plant sensitivity to increased UV-B irradiance: effects on growth, gas-exchange and pigmentation of bean plants (Phaseolus vulgaris L.). Plant, Cell Environ. 17: 295–301.Google Scholar
- Dumpert, K. & Knacker, T. 1985. A comparison of the effects of enhanced UV-B radiation on crop plants exposed to greenhouse and field conditions. Biochemy Physiol. Pflanzen 180: 599–612.Google Scholar
- Flint, S. D. & Caldwell, M. M. 1998. Solar UV-B and visible radiation in tropical forest gaps: measurements partitioning direct and diffuse radiation. Global Change Biol. 4: 863–870.Google Scholar
- Flint, S. D., Jordan, P.W. & Caldwell, M. M. 1985. Plant protective response to enhanced UV-B radiation under field conditions: leaf optical properties and photosynthesis. Photochem. Photobiol. 41: 95–99.Google Scholar
- Grant, R. H. 1991. Agroclimatology and modeling. Ultraviolet and photosynthetically active bands: plane surface irradiance at corn canopy base. Agron. J. 83: 391–396.Google Scholar
- Grant, R. H. 1997. Partitioning of biologically active radiation in plant canopies. Int. J. Biometeorol. 40: 26–40.Google Scholar
- Greenberg, B. M., Wilson, M. I., Gerhardt, K. E. & Wilson, K. E. 1996. Morphological and physiological responses of Brassica napus to ultraviolet-B radiation: photomodification of ribulose-1,5-bisphosphate carboxylase/oxygenase and potential acclimation processes. J. Plant Physiol. 148: 78–85.Google Scholar
- Jenkins, G. I. 1997. UV-B and blue light signal transduction in Arabidopsis. Plant Cell Environ. 20: 733–778.Google Scholar
- Jones, H. G. 1992. Plants and Microclimate. Cambridge University Press, Cambridge.Google Scholar
- Moran, R. 1982. Formulae for the determination of chlorophyllous pigments extracted with N,N-dimethylformamide. Plant Physiol. 69: 413–416.Google Scholar
- Rozema, J., Van de Staaij, J., Björn, L. O. & Caldwell, M. 1997. UV-B as an environmental factor in plant life: stress and regulation. Trees 12: 22–28.Google Scholar
- Sinoquet, H., Rakocevic M. & Varlet-Grancher C. 2000, Comparison of models for daily light partitioning in multispecies canopies. Agric. Forest Meteorol. 2774: 1–13.Google Scholar
- Teramura, A. H. 1980. Effects of ultraviolet-B radiation on soybean. I. Importance of photosynthetically active radiation in evaluating ultraviolet-B irradiance effects on soybean and wheat growth. Physiol. Plant. 49: 333–339.Google Scholar
- Teramura, A. H. & Sullivan, J. H. 1994. Effects of UV-B radiation on photosynthesis and growth of terrestrial plants. Photosynth. Res. 39: 463–473.Google Scholar