Ultrastructure and photosynthetic apparatus of Rhodella violacea (Porphyridiales, Rhodophyta) grown under iron-deficient conditions
1999
Marquardt, Jürgen | Schultze, Albrecht | Rosenkranz, Vera | Wehrmeyer, Werner
We analyzed the effects of iron deficiency on the ultrastructure and biochemical composition of the photosynthetic apparatus of the marine alga Rhodella violacea (Kornmann) Wehrmeyer (Porphyridiales, Rhodophyta). Iron deficiency, lasting for up to 12 wk, caused a drastic reduction of the thylakoid surface area per cell. The chlorophyll content of the cells decreased to approximately 2% of the original level, whereas the carotenoids were reduced to about 12%. Photosystem I was severely affected. The ratio of photosystem I to photosystem II decreased in iron-deficient cells from 2.3 to 0.5. Polypeptides of photosystem II and of the light-harvesting complex of photosystem I were reduced in a nonstoichiometric way. The 77-K fluorescence emission maximum of the algae shifted from 716 to 709 nm. Phycobilisomes that were morphologically indistinguishable from those in control cells were present in electron microscopic images even at the final stage of iron starvation. However, the ratio of phycoerythrin to phycocyanin decreased from about 2.1 to 1.5. Polypeptides corresponding to the cyanobacterial isiA gene product were not detected.
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