Two different strategies of Mediterranean macchia plants to avoid photoinhibitory damage by excessive radiation levels during summer drought |
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| Institution: | 1. Lehrstuhl für experimentelle Ökologie und Ökosystembiologie, Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany;2. Departamento de Biologia Vegetal, Faculdade Ciěncias, Universidade Lisboa, Campo Grande, C2, 4 Piso, P-1700 Lisboa, Portugal;1. Department of Analytical Chemistry, University of Granada, c/Fuentenueva s/n, E-18071 Granada, Spain;2. Research and Development of Functional Food Centre (CIDAF), PTS Granada, Avda. Del Conocimiento s/n., Edificio BioRegion, E-18016 Granada, Spain;3. Department of Food Biosciences, The University of Reading, Whiteknights, Reading, RG6 6AP, United Kingdom;4. Skin Research Platform (SRP), Institute of Molecular and Cell Biology (IBMC), University Miguel Hernández, Avda. De la Universidad s/n, E-03202 Elche, Alicante, Spain;1. School of Statistics, Dongbei University of Finance and Economics, Dalian, China;2. School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, China;3. Faculty of Engineering and Information Technology, University of Technology, Sydney, Australia;1. National Research Council of Italy ? Tree and Timber Institute, (CNR ? IVALSA), Via Madonna del Piano 10 Sesto Fiorentino, 50019 Firenze, Italy;2. Dipartimento di Agricoltura, Alimentazione e Ambiente (Di3A), Università degli Studi di Catania, via Valdisavoia 5, 95123 Catania, Italy;3. Department of Agrifood Production and Environmental Sciences (DiSPAA), University of Florence, Viale delle Idee 30, 50019 Sesto Fiorentino, Firenze, Italy;4. National Research Council of Italy ? Department of Biology, Agriculture and Food Sciences (CNR-DISBA), Rome, Italy;1. National Research Institute of Agronomy (INRA), UMR 1391 ISPA, 33140 Villenave d’Ornon, France;2. National Research Institute of Agronomy (INRA), UMR 1391 ISPA, 33610 Cestas, France;3. National Research Institute of Agronomy (INRA), UEFP, 33610 Cestas, France;4. National Research Institute of Agronomy (INRA), Bordeaux Science Agro (BSA), UMR 1391 ISPA, 33140 Villenave d’Ornon, France;5. Bordeaux INP, EA 4592, G&E, 33600 Pessac, France;6. Univ. Bordeaux Montaigne, EA 4592, G&E, 33600 Pessac, France |
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| Abstract: | The adaptive strategies to high radiation and water stress of the drought tolerant evergreen sclerophylls Quercus coccifera and Arbutus unedo are compared to those of the semi-deciduous Cistus spp. (C. albidus and C. monspeliensis). Cistus spp. partially avoided drought by a marked reduction of their transpirational surface through leaf abscission during summer, when predawn water potential declined below -5.5 MPa. Chlorophyll fluorescence measurements revealed a reversible diurnal decrease of maximum photochemical efficiency of PSII (Fv/Fm), which became more accentuated during summer drought in all species. An important strategy to avoid damage by excessive radiation levels in Cistus spp. was the structural regulation of light interception through leaf angle changes, from a more horizontal orientation in spring (< 35°) to a more vertical orientation in summer (> 70°). Horizontal orientated leaves were highly susceptible to photoinhibition, and excessive radiation often resulted in irreversible photodamage followed by leaf abscission during summer, whereas vertical leaf orientation appeared to protect the leaf from severe photoinhibition. Still, these mechanisms were not fully successful in avoiding chronic photoinhibition, and predawn Fv/Fm values remained low in Cistus spp. during summer (only exhibiting a partial overnight recovery). Evergreen sclerophylls were less susceptible to photoinhibition, and the diurnal decline in Fv/Fm remained fully reversible during drought. Structural regulation of light interception was not found to be an important strategy in these species, and only small, though significant changes in leaf angle occurred. The ecological importance of the adaptive strategies of each functional group is discussed. |
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