EFFECT OF LIGHT INTENSITY ON PHOTOSYNTHESIS BY THERMAL ALGAE ADAPTED TO NATURAL AND REDUCED SUNLIGHT1
Thermal algae in alkaline hot springs of Yellowstone National Park (Wyoming) grow as compact mats in which self‐shading is extensive, as shown by measurement by autoradiography of photosynthetic activity of cells at different levels in the mat. The effect of light intensity on photosynthesis of the...
| Published in: | Limnology and Oceanography |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
1969
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.4319/lo.1969.14.3.0334 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flo.1969.14.3.0334 https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1969.14.3.0334 |
| Summary: | Thermal algae in alkaline hot springs of Yellowstone National Park (Wyoming) grow as compact mats in which self‐shading is extensive, as shown by measurement by autoradiography of photosynthetic activity of cells at different levels in the mat. The effect of light intensity on photosynthesis of the algal mats was studied using neutral density filters during incubation with 14 CO 2 . Despite the intense sunlight at the altitude of Yellowstone, light inhibition by full sunlight was observed only occasionally; the rate of photosynthesis fell progressively with decreasing light, although the most efficient use was at 7–14% of full sunlight. Later, the light intensity over portions of the algal mats was reduced to 18% of full sunlight by installing neutral density glass plates, and changes of chlorophyll content, cell number, and response of photosynthesis to light intensity were determined over the next year. Although the chlorophyll content of the algae at the surface of the mat rose quickly, the chlorophyll content of the mat as a whole rose slowly or not at all; the photosynthetic response of the algal mats to full and reduced sunlight also changed slowly or not at all. Although individual algal cells can adapt rapidly to changes in light, the entire population, because of its existence in compact mats, adapts slowly. At the latitude of Yellowstone there is sufficient light throughout the year to enable algal growth to occur even at temperatures near the upper limit at which blue‐green algae can grow; in Iceland, hot spring algae cannot grow during several winter months. Natural ultraviolet radiation neither inhibited nor stimulated photosynthesis. |
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