© 2007 Heron Publishing—Victoria, Canada
Drought-induced oxidative stress in Canarian laurel forest tree species growing under controlled conditions
Manuel Sánchez-Díaz (1), Carolina Tapia (1) and M. Carmen Antolín (1, 2)
1. Departamento de Biología Vegetal. Facultades de Ciencias y Farmacia. Universidad de Navarra. Irunlarrea s/n, 31008 Pamplona,
Spain / 2. Corresponding author (cantolin@unav.es) / Received November 27, 2006; accepted January 11, 2007; published online July 3, 2007
Summary
We studied photoprotection and antioxidative protection in the three major species of the Canarian laurel forest (Laurus azorica (Seub.) Franco, Persea indica (L.) K. Spreng and Myrica faya Aiton). Trees were exposed to drought under controlled conditions by withholding water until leaf relative water content
(RWC) reached 50–55%. Drought reduced photosynthetic rate (PN) and was associated with decreased quantum yield of photosystem II (PSII) electron transport and increased non-photochemical
quenching (NPQ) in L. azorica and M. faya, but did not increase NPQ in P. indica. Drought-treated trees of L. azorica had the highest de-epoxidation state (DPS) of the xanthophyll cycle and the highest zeaxanthin (Z) concentration, suggesting that this species had more effective photoprotective mechanisms than M. faya and P. indica. Moreover, β-carotene remained unaltered in L. azorica trees during drought, suggesting that the chloroplasts of this species are better protected against oxidative stress than
those of M. faya and P. indica. Increased antioxidation by ascorbate peroxidase, superoxide dismutase and glutathione reductase in L. azorica removed activated oxygen species (AOS) generated during drought treatment. Although M. faya was able to increase its energy dissipation rate by forming Z and thus increasing the DPS of the xanthophyll cycle, it did not respond to drought-induced oxidative stress with the result
that β-carotene degradation occurred. Persea indica did not activate an energy dissipation mechanism in response to drought treatment, hence formation of AOS was likely high
in the drought-treated trees. In general, L. azorica was most resistant and P. indica most sensitive to photoinhibition and oxidative stress during drought.
Keywords:
antioxidant enzymes, photosynthesis, water deficit, xanthophyll cycle.
