Abstract
Japanese laver (Porphyra tenera KJELLMAN) growing high in the intertidal zone is continuously exposed to rather drastic changes in various physiological and ecological factors such as salinity, temperature, pH and dryness. The algal respiration as affected by those factors was investigated by manometric technique using 200mg each in fresh weight of the alga put in normal and condensed or diluted sea water in the vessel. Results obtained are the following: 1) Respiration increases when sea water is diluted to half strength, and decreases under extremely hypertonic and hypotonic conditions. But the trend varies depending on the temperature. Respiration steadily increases with rising temperature from 15° to 30°C irrespectively of the salt concentration. Elevation to 35°C depresses respiration unless kept under hypertonic condition. 2) The alga shows meaurable oxygen uptake even without water in the vessel when measured after drying for short period. Respiration recovers or increases rapidly when the alga is returned to water after prolonged drying. 3) Changes in pH (5.0-10.0) do not seriously affect the respiration. 4) Qo2 (μ/mg dry wt./hr.) in normal sea water is 1.58 at 25°C and 3.27 at 35°C. Respiratory quotient (R. Q.)is about 0.8, showing minor differences under different conditions.
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