| Popis: |
Cultures of Phaeodactylum tricornutum were exposed to combinations of visible and ultraviolet-B (UV-B) light intensities in the laboratory, the ultraviolet light (UV) sources being fluorescent lamps whose peak emission was at approximately 310 nm. Filters of cellulose acetate and Mylar were used to attenuate the UV-B intensity, the latter absorbing all the radiation in the 310 nm region. The growth rates of the algae were calculated from chlorophyll analyses made during the exponential growth of the cultures, and trace gas measurements were made after a fixed time (44 h). Algal cells exposed to a UV-B flux approximately one-fifth that of average sunlight intensity, with visible light intensities optimal for photosynthesis, underwent a 20 percent reduction in growth rate and were completely inhibited by UV fluxes half that of sunlight. A major finding of the trace gas analyses was that carbon monoxide (CO) formation was relatively constant over the range of UV fluxes imposed. Previous experiments with outdoor exposures had produced CO in concentrations of an order of magnitude higher. It appears that UV-B was not the causative agent for the unsually high CO production resulting from exposure of the algae to sunlight. |
