© 2007 Heron Publishing—Victoria, Canada
Dynamics of violaxanthin and lutein epoxide xanthophyll cycles in Lauraceae tree species under field conditions
Raquel Esteban (1), Eduardo T. Jiménez (2), M. Soledad Jiménez (2), Domingo Morales (2), Koldobika Hormaetxe (1), José María Becerril (1) and José Ignacio García-Plazaola (1, 3)
1. Departamento de Biología Vegetal y Ecología, Universidad del País Vasco EHU, Apdo. 644, E-48080 Bilbao, Spain / 2. Departamento de Biología Vegetal, Universidad de La Laguna, 38207-La Laguna, Tenerife, Spain / 3. Corresponding author (gvpgaplj@lg.ehu.es) / Received November 20, 2006; accepted February 7, 2007; published online July 3, 2007
Summary
Two xanthophyll cycles have been described in higher plants: the violaxanthin xanthophyll (V or VAZ) cycle, which is present
in all species, and the taxonomically restricted lutein epoxide xanthophyll (Lx) cycle, which involves the light-induced de-epoxidation
of Lx to lutein (L) and its epoxidation back to Lx in low light. Laboratory experiments indicate that the first reaction occurs
quickly, but the second reaction is much slower. We investigated the Lx cycle under field conditions in several tree species
of the Lauraceae family to determine its relationship with the ubiquitous V cycle. The field study was conducted in two natural
laurel forests: one in the Canary Islands, where Laurus azorica (Seub.) Franco, Ocotea foetens (Aiton.) Benth, Apollonias barbujana (Cav.) Bornm. and Persea indica (L.) Spreng were studied; and one in the Basque Atlantic coast where Laurus nobilis L. was studied. The results were complemented by a taxonomic study. The presence of Lx was widespread among Lauraceae species,
but its concentration varied even among closely related species. The V pool size correlated positively with growth irradiance,
whereas the relationship between Lx pool size and growth irradiance varied with species. A functional Lx cycle was confirmed
under field conditions only in O. foetens and L. nobilis. Furthermore, in O. foetens, a correlation between Lx de-epoxidation and photoinhibition suggested a protective role for this cycle. We conclude that,
unlike the V cycle, which is normally correlated with irradiance, the operation and light dependence of the Lx cycle is species-dependent.
Keywords:
de-epoxidation, laurel forest, Laurus, Ocotea, photoinhibition, photoprotection.
