Photosynthesis and respiration of Gracilaria salicornia (Gracilariales, Rhodophyta) from Thailand and Japan
2006
Phooprong, S. | Ogawa, H., Kitasato Univ., Iwate 022-0101 (Japan). School of Fisheries Science
Common species growing in tropical and subtropical waters, Gracilaria salicornia collected from Okinawa of Japan and Rayong Province of Thailand, were used for the measurement of photosynthetic and respiratory rates under various conditions of irradiance, salinity and temperature. The following results were obtained from Thai and Japanese plants: 1) Photosynthetic and respiratory responses rose with temperature elevation in the range of 20 and 35 deg C. 2) Salinity variation did not show any significant effect on respiratory rates. 3) Light-saturation without photo-inhibition occurred from the ranged of 200 to 710 micro mol/sq m/s. These results indicated that both plants have broad tolerance potential in photosynthetic response to environmental charges. On the other hand, significant differences were obtained in the photosynthetic and respiratory rates of both algae. Algae from Thailand showed higher values in photosynthetic rate (3-12 mg O2 dwg/h) and respiratory rate (0.2-0.6 mg O2 dwg/h) than those from Japan. Parameters derived from the photosynthesis-light curve, light-saturated photosynthetic rate (P sub max), photosynthetic efficiency (alpha), initial saturation irradiance (I sub k) and compensation point (I sub c), were higher in the plants from Thailand than those from Japan. These results indicate that Thai algae have higher photosynthetic potential under conditions of strong light and high temperature than Japanese algae. Such characteristics in photosynthesis and respiration may have a relation to the environmental conditions of their habitat, because the salinity variation at both places is not so different, and sometimes similar, but light and temperature variations are very wide because of the difference in latitude.
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