The Temperature Coefficient of the Duration of Life of Ceramium tenuissimum

Abstract

Reaction velocities at various temperatures have become of much interest to biologists, on account of the possibility they present for the identification of certain physiological processes as chemical or physical, since it has been found that certain common physical and chemical reactions have rather characteristic temperature coefficients. Thus, if we suspect that a certain reaction is due to a chemical process, we can determine whether or not the velocity of the reaction at various temperatures is of the magnitude demanded by a chemical reaction. Since the temperature coefficients for all chemical reactions do not always have the same order of magnitude as demanded by the van't Hoff rule on the dependence of the rate of reaction of chemical processes upon temperature (9), the test is not wholly conclusive, but indicates rather a probable explanation of the phenomenon in question. Animal physiologists in recent years have given much attention to temperature coefficients, but very little work has been done upon this subject by plant physiologists. CLAUSEN (2) was the first to show that the rate of evolution of carbon dioxide from seedlings and buds was about doubled with an increase of io? C. M\IiSS MATTHAEI (5) found that van't Hoff's rule applied to the fixation of carbon dioxide by leaves in sunlight and to the evolution of this gas by leaves in the dark. PRICE (7) determined the temperature coefficient for the opening of flower buds, and found it to have the magnitude demanded for a chemical reaction. It will be seen that these experiments deal with growth phenomena. LOEB (4) was the first to call attention to the fact that the temperature coefficient of the duration of life of sea urchin eggs differs widely from that of their development, the temperature coefficient of development being 2.86 for a rise in temperature of Io' C., while that of duration of life is nearly 2 for a rise in temperature of i? C. MOORE (6) found that the temperature 65] [Botanical Gazette, vol. 62