A SMALLER AND IMPAIRED XANTHOPHYLL CYCLE MAKES THE DEEP SEA MACROALGAE LAMINARIA ABYSSALIS (PHAEOPHYCEAE) HIGHLY SENSITIVE TO DAYLIGHT WHEN COMPARED WITH SHALLOW WATER LAMINARIA DIGITATA 1

• Published in: Journal of phycology Vol. 38; no. 5; pp. 939 - 947
• Main Authors: Rodrigues, Marcoaurélio Almenara, Dos Santos, César Pereira, Young, Andrew John, Strbac, Dragana, Hall, David Oakley
• Format: Journal Article
• Language: English
• Published: 01-10-2002
• ISSN: 0022-3646; 1529-8817
• DOI: 10.1046/j.1529-8817.2002.t01-1-01231.x

Pigment composition, fluorescence parameters, and oxygen evolution of the deep water
Laminaria abyssalis
Oliveira and of the shallow water
L. digitata
Lamoroux were determined in response to high irradiances. This was performed in the presence and absence of an inhibitor of violaxanthin de‐epoxidase (dithiothreitol) or an inhibitor of the chloroplast‐encoded protein synthesis (chloramphenicol). Photochemical quenching in
L. digitata
was almost 3‐fold that seen in
L. abyssalis
, whereas both nonphotochemical quenching and PSII photochemical yield were doubled.
Laminaria digitata
possessed a xanthophyll‐cycle pool nearly double that of
L. abyssalis
. After photoinhibitory treatment,
L. digitata
displayed substantial violaxanthin de‐epoxidation, whereas in
L. abyssalis
de‐epoxidation only took place in limited amounts. Both species were able to fully recover their epoxidation status after transfer back to dim light. Overnight incubation with dithiothreitol fully blocked de‐epoxidation in both species, and both displayed similar fluorescence properties. Chloramphenicol caused no change in their fluorescence parameters. With high light treatment,
L. abyssalis
was completely and irreversibly inhibited both in the presence and absence of inhibitors, whereas
L. digitata
showed 60% inhibition of its photosynthetic activity and full recovery in the absence of inhibitors. In the presence of dithiothreitol,
L. digitata
did not recover to the preillumination conditions and chloramphenicol delayed the recovery of the oxygen evolution activity. We suggest that the xanthophyll cycle is the main mechanism of photoprotection of these
Laminaria
species and that the higher susceptibility of
L. abyssalis
to photoinhibition may be due to its limited de‐epoxidation capacity and reduced xanthophyll‐cycle pool size.