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Abstract

Influences of hydostatic pressure (600atm) , temperature (50, 150 and 300 C ) and O2 concentration (3 410 % of air saturation ) of the outer medium were studied on the rate of O2 exchange of porphyra umbilicalis collected from heligoland (north sea ) . the O2 tension acted antagonistically to the pressure effects. The pressure influenced rates of respiration and apparent photosynthetics decreased gradually with a decrease in the O2 concentration and vice versa ; the effects on photosynthesis, however, were lesser than those on respiration. The O2 concentration of 30% was found to be critical, at higher values repiration of the pressure affected algae increased whereas at lower values it decreased as compared to control . At O2 concentration lower than 15% , the rate of O2 exchange decreased very sharply . the pressure influences were retarded by higher and intensified by lower temperatures.

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