Physiological Responses of Phytoflagellates to Dissolved Organic Substrate Additions. 1. Dominant Role of Heterotrophic Nutrition in Poterioochromonas malhamensis (Chrysophyceae)

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Algal heterotrophy is a potentially important consideration in the flow of carbon through aquatic food webs. The physiological responses to organic compound additions under various light intensities were examined with Poterioochromonas malhamensis, a freshwater chrysophyte with an exceptionally high heterotrophic capability. P. malhamensis demonstrated a much greater potential for heterotrophic growth than for photoautotrophic growth. When organic substrates (glucose, glycerol, or ethanol) were added to the culture medium, the growth rate of P. malhamensis significantly increased while the chlorophyll a content cell^<-1> decreased, even at light intensities saturating for photoautotrophic growth. After an initial decline in chlorophyll production caused by organic substrate uptake, chlorophyll a cell^<-1> increased and the uptake rate of organic substrates decreased, despite the persistence of a relatively high substrate concentration in the medium. The results are consistent with the production of substance(s) by P. malhamensis that conditioned the culture medium, leading to a relief of the inhibitory effect of organic substrates on chlorophyll production.
日本植物生理学会の論文