EVOLUTION OF PS II-ALPHA AND PS II-BETA CENTERS DURING THE GREENING OF EUGLENA-GRACILIS Z - CORRELATIONS WITH CHANGES IN LIPID-CONTENT

The building up of the two types of reaction centers, PS II alpha and PS II beta, was investigated during the greening of Euglena gracilis Z cells in resting medium. The maximal values in the proportion of PS II alpha centers (55%) and in the oxygen evolved per chlorophyll were reached at the outbreak of greening, when accumulation of galactolipids (MGDG and DGDG) rich in unsaturated fatty acids occurred, and when anionic lipids (SQDG and PG) emerged. As the greening progressed, the chlorophyll accumulation corresponded to a secondary enrichment in PS II beta centers, which built up more rapidly than PS II alpha centers; correlatively, a general saturation of the fatty acids constitutive of all lipid classes took place.