Studies of the Cultural Physiology of the Lichen Alga <i>Trebouxia</i>

Abstract

Abstract The pholosynthetic growth of three species of Trebouxia was so slow as to preclude the usual inorganic methods of algal cultivation. Heterotrophic growth was much stronger — as many as 0.4 doublings per day were obtained in Bold's solution with glucose and amino acid hydrolysates. Ammonium salts of inorganic acids could not be used in the culture medium because they caused excessive reductions in pH. Although the organisms showed variations in their growth response to amino acids, no specific requirement was found. T. erici produced significantly lower quantities of photosynthetic pigments in the dark. Of the nineteen carbohydrates tested, only glucose, mannitol, and galactosc stimulated growth of the algae. Preliminary studies showed that Trebouxia incorporated 14 CO 2 more slowly than Chlorella pyrenoidosa . However, the carbon fixed by Trebouxia remained soluble in 80% ethanol longer than Chlorella. The carbon incorporated as CO 2 in short term experiments was greater than would be expected from the growth rates of the organisms studied.