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Darkness, lack of oxygen, and an acidic medium promote forniatioa of a pheophytin-like pigment from chlorophyll in Euglena. I n an attempt to elucidate the metabolic basis for this alteration, we have employed a number of metabolic poisons. Dinitrophenol, in an acidic medium, produces similar but more drastic pigment changes. The extent of pigment decay is dependent on dinitrophenol concentration, pH, light, and oxygen. Inhibition of the contractile vacuole, volnnie changes of the organism, and major structural alterations of the chloroplast acconipany the pigment decay.
Of other metabolic poisons investigated, pentachlorophenol, iodoacetaniide, sodium fluoride, and sodium azide produce similar pigment degradation. Malonic acid is ineffective.
This general type of pigment decay is most simply explained as an accumulation of acid in the organism. The active transport of hydrogen ions in relation to the contractile vacuole and cell wall will be considered. TEMPERATURE AND THE NON-LUMINESCENT OXIDATION OF CYPRIDINA LUCIFERIN.'
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