Photoinhibition in Thylakoids and Intact Chloroplasts of Codium fragile (Suringar) Hariot
There is a general acceptance in the literature that photosystem II (PSII) is the primary site of photoinhibition and that prolonged exposure to excessive photosynthetic photon flux density (PPFD) results in pigment loss and lipid breakdown due to photooxidation (as reviewed in 1). However, growth of the marine alga C. fragile is adapted to low PPFD (2,3,4) even though its intertidal habitat is regularly exposed to wide extremes of PPFD on both a seasonal and daily basis. Therefore, this alga is especially at risk of photoinhibition and photooxidation at the higher PPFD’s occurring at low tide. Experiments described in this paper illustrate that chloroplasts and thylakoids isolated from this alga photoinhibit at irradiances supra-optimal for photosynthesis (PS). As with other photosynthetic organisms, the primary lesion appears to be associated with PSII and photooxidative damage occurs with prolonged exposure to light.
KeywordsPhotosynthetic Photon Flux Density PSII Activity Intertidal Habitat Intact Chloroplast Photooxidative Damage
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