Physiological Studies on Diurnal Biological Rhythms of Porphyra-II

The Growth and the Contents of Free and Total Nitrogen and Carbohydrate inthe Thallus Cultured in the Laboratory

Abstract

The surface area, the fresh and dry weights, the contents of total free amino acids and total nitrogen, and the total alcohol soluble and insoluble carbohydrates in the thallus of porphyra sp. Cultured in an artificial medium were derermined during its growth under 12-hour light and dark cycles. The thallus area and dry weight doubled during a 72 hr culture period, and particularly showed greater increases during the light. In contrast to the remarkable decrease of nitrate nitrogen in the medium, the total nitrogen in the thallus increased showing a reverse relationship. The nitrate uptake was much greater on a dry weight basis was almost unchanged during the culture period.
The total alcohol-soluble and insoluble carbohydrates, and the total free amino acids also increased in amount during the light culture and attained their maxima at the end of the light periods but followed by a steep decrease which began immediately after dark. Their minimum coutents were found at the end of the dark periods, The possible cause of such rhythmic changes in these compounds were discussed in relation to photosynthesis of the thallus and its cell growth and division.