Changes in the photosynthetic pigment patterns during the synchronous life cycle of Porphyridium purpureum
Kopecký, Jiří; Lukavská, Alena; Verboviková, Elena; Pfündel, Erhard
published: Dec 1, 2004
ArtNo. ESP142015400009, Price: 29.00 €
Photosynthetic pigments biosynthesis (chlorophyll a and carotenoids) during the synchronous cycle of the unicellular red alga Porphyridium purpureum was studied. The culture was synchronised by a light/dark regime. We found the shortest possible time of light period of cell cycle at given culture condition (80 W.m−2 white light, 24 °C) to be 8 h 45 min. This length of light period of cell cycle represent value of specific growth rate μMAX=0.083. During the cell cycle of P. purpureum the biosynthesis of chlorophyll a, as an integral part of the photosynthetic apparatus, starts immediately upon daughter cells release and continues within the whole light period of the cell cycle. The most abundant carotenoids zeaxanthin and β-carotene together with traces of β-cryptoxanthin are initially synthesized during the light period of the cell cycle. Although the main fraction of β-carotene appears to be inserted in the reaction centers, a part of the total pool of β-carotene is rapidly converted to β-cryptoxanthin. Further conversion of β-cryptoxanthin to zeaxanthin reaches the maximal value around the 4th hour of light period of the cell cycle. Because the alga P. purpureum has no chlorophyll b and no accessory light harvesting chlorophyll a/b protein complexes, the function of zeaxanthin, in contrast to β-carotene as primary component of the photosynthetic apparatus, still remains faintly disputatious.