Growth under red light enhances phototsystem II relative to photosystem I and phycobilisomes in the red alga Porphyridium cruentum
- Univ. of Maryland, College Park (USA)
- Department of Agriculture, Peoria, IL (USA)
Acclimation of the photosynthetic apparatus to light absorbed primarily by photosystem I (PSI) or by photosystem II (PSII) was studied in the unicellular red alga Porphyridium cruentum (ATCC 50161). Cultures grown under green light of 15 microeinsteins per square meter per second (PSII light; absorbed predominantly by the phycobilisomes) exhibited a PSII/PSI ratio of 0.26 {plus minus} 0.05. Under red light (PSI light; absorbed primarily by chlorophyll) of comparable quantum flux, cells contained nearly five times as many PSII per PSI, and three times as many PSII per cell. About 12% of the chlorophyll was attributed to PSII in green light, 22% in white light, and 39% in red light-grown cultures. Chlorophyll antenna sizes appeared to remain constant at about 75 chlorophyll per PSII and 140 per PSI. Spectral quality had little effect on cell content or composition of the phycobilisomes, thus the number of PSII per phycobilisome was substantially greater in red light-grown cultures than in those grown under green or white light. Total photosystems (PSI + PSII) per phycobilisome remained at about eight in each case. Zeaxanthin comprised more than 50% (mole/mole), {beta}-carotene about 40%, and cryptoxanthin about 4% of the carotenoid pigment.
- OSTI ID:
- 5852992
- Journal Information:
- Plant Physiology; (USA), Vol. 93:3; ISSN 0032-0889
- Country of Publication:
- United States
- Language:
- English
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