Use of a solid support in the study of photosynthetic activity of the cyanobacterium Spirulina platensis

Oxygen evolution activity of Spirulina platensis cells ttached to nitro-cellulose filters or glass fiber filters (GF/C) was measured using the leaf disc electrode (LD-2 Hansatech Ltd, Kings Lynn, U.K.), originally designed for its use with leaves of higher plants. Measurements were performed in saturating (CO2) as described previously for leaf discs and pieces. Photoinhibition could be induced in cells on the solid support as indicated by a significant increase in their quantum requirement (from 11 to 33 after 25 min exposure to a photon flux density of 2500 mu E m(-2)s(-1) and a smaller effect on the photosynthetic rate at light saturation. Photoinhibited cells showed recovery from the photoinhibitory treatment when illuminated under dim light.