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Effects of Light Intensity and Temperature on Photosynthesis and Respiration of Two East Antarctic Mosses, Bryum argenteum and Bryum antarcticum

James R. Rastorfer
The Bryologist
Vol. 73, No. 3 (Autumn, 1970), pp. 544-556
DOI: 10.2307/3241493
Stable URL: http://www.jstor.org/stable/3241493
Page Count: 13
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Effects of Light Intensity and Temperature on Photosynthesis and Respiration of Two East Antarctic Mosses, Bryum argenteum and Bryum antarcticum
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Abstract

Gametophytes from Victoria Land were tested in the laboratory at McMurdo Station, Antarctica. Net photosynthetic and respiratory rates were determined by measuring oxygen exchange in air containing 1% CO2 (v/v) with respirometers. Optimal temperatures for net photosynthesis were 25-30°C and 15-20°C with maximal rates of 117 and 27-37 μliters O2 evolved hr-1 cm2 for Bryum argenteum and B. antarcticum, respectively, whereas the respiratory rates increased with increasing temperatures throughout the temperature ranges tested. In both species, light compensation points were ca. 1.6 mW cm2 and light saturation points were reached at 8-10 mW cm2 when determined at 15°C, but shifted to about one half these values when determined at 5°C. However, higher rates of net photosynthesis were obtained at 5°C and light intensities less than 4 mW cm-2 for B. argenteum and less than 3 mW cm-2 for B. antarcticum as compared to rates measured at 15°C and low light intensities. Field observations indicated that direct sunlight adversely affects chlorophyll contents of B. antarcticum, but under conditions of low light intensities, a dark period, and nutrient supply an increase in chlorophyll content was obtained in samples collected from the field. Apparently, these mosses do not require low temperatures or high light intensities to survive the harsh antarctic environment, but have a capacity to endure these conditions.

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