The photodynamic action of eosin, a singlet-oxygen generator : Some effects on leaf tissue of Pisum sativum L.

Eosin, a xanthene dye capable of the photodynamic generation of singlet oxygen ((1)O2), was shown to promote injury to leaf tissue of Pisum sativum L. in the presence of visible light. Chloroplasts appeared particularly sensitive to this action, displaying a rapid inactivation of photosynthesis. Investigation of chloroplast disruption involved analysis of pigment loss, ribulose 1,5-bisphosphate carboxylase (EC 4.1.1.39) activity, NADPH-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) activity, photosynthetic electron transport and ultrastructural examination. The initial loss of photosynthetic activity was associated with damage to the thylakoid membranes. Early stages of damage were accompanied by the production of ethane.