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 μE m^-2s^-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.