title: How sensitive is Melissa officinalis to realistic ozone concentrations?
abstract: Lemon balm (Melissa officinalis, L.; Lamiaceae) was exposed to realistic ozone (O3) dosages (80 ppb for 5 h), because high background levels of O3 are considered to be as harmful as episodic O3 regimes. Temporal alterations of different ecophysiological, biochemical and structural parameters were investigated in order to test if this species can be considered as an O3-bioindicator regarding changes in background concentrations. At the end of ozone exposure, the plants did not exhibit any visible foliar symptoms, as only at microscopic level a small number of dead cells were found. Photosynthetic processes, however, were significantly affected. During and after the treatment, ozone induced a reduction in CO2 fixation capacity (up to 52% after 12 h from the beginning of the treatment) due to mesophyllic limitations. Intercellular CO2 concentration significantly increased in comparison to controls (+90% at the end of the post-fumigation period). Furthermore impairment of carboxylation efficiency (-71% at the end of the post-fumigation period compared to controls in filtered air) and membrane damage in terms of integrity (as demonstrated by a significant rise in solute leakage) were observed. A regulatory adjustment of photosynthetic processes was highlighted during the post-fumigation period by the higher values of qNP and (1-q(P)) and therefore suggests a tendency to reduce the light energy used in photochemistry at the expense of the capacity to dissipate the excess as excitation energy. In addition, the chlorophyll a/b ratio and the de-epoxidation index increased, showing a rearrangement of the pigment composition of the photosynthetic apparatus and a marked activation of photoprotective mechanisms.
authors: Institut für Pharmazeutische Biologie und Biotechnologie, Philipps-Universität Marburg, Deutschhausstr. 17A, D-35037 Marburg, Germany.
authors: Anne Sarah
authors: AS
authors: Döring
authors: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors: Elisa
authors: E
authors: Pellegrini
authors: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors: Alessandra
authors: A
authors: Campanella
authors: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors: Alice
authors: A
authors: Trivellini
authors: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors: Clizia
authors: C
authors: Gennai
authors: Institut für Pharmazeutische Biologie und Biotechnologie, Philipps-Universität Marburg, Deutschhausstr. 17A, D-35037 Marburg, Germany.
authors: Maike
authors: M
authors: Petersen
authors: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy. Electronic address: cristina.nali@unipi.it.
authors: Cristina
authors: C
authors: Nali
authors: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors: Giacomo
authors: G
authors: Lorenzini
mesh_terms: D004305:Dose-Response Relationship, Drug; D031334:Melissa / Q000187:drug effects*; D010126:Ozone / Q000494:pharmacology*
chemical_list: D010126:Ozone
keywords: 1-qP; 3,3′-diaminobenzidine; A(max); A(sat); ABA; ANOVA; BSA; C(i); CAFE; Chl a/b; Chl a + b; Clean Air for Europe; DAB; DBPA; DEPS; E; EC; ELISA; F(0); F(m); F(s); F(v)/F(m); FBE; G(w); ITE; J(max); LHCPs; Leaf symptoms; Lemon balm; MDA; Membrane integrity; Oxidative stress; PAR; PFD; PPFD; PSI; PSII; PSII photochemistry; Photosynthesis; R(d); RH; RWC; RuBP; Rubisco; TBA; TBARS; TPU; V(cmax); VPD; abscisic acid; actual quantum yield of PSII; air vapor pressure deficit; apparent quantum yield; bovine serum albumin; chlorophyll a/chlorophyll b; chlorophyll a + chlorophyll b; daytime respiration; de-epoxidation index; decoring-binding protein A; electron conductivity of leaf disc leachates; enzyme linked immunosorbent assay; from the beginning of exposure; instantaneous transpiration efficiency; intercellular CO(2) concentration; light-harvesting complex proteins; light-saturated rate of electron transport; malondialdehyde; maximal fluorescence; maximal fluorescence in the light-adapted state; maximum level of photosynthetic activity; maximum rate of carboxylation; minimal fluorescence; minimal fluorescence in the light-adapted state; non-photochemical quenching; one-way analysis of variance; photochemical quenching; photon flux density; photosynthetic activity at saturating light level; photosynthetic photon flux density; photosynthetically active radiation; photosystem I; photosystem II; qNP; qP; quantum efficiency; reduction state of Q(A); relative humidity; relative water content; ribulose 1,5-bisphosphate; ribulose-1,5-bisphosphate carboxylase/oxygenase; steady-state fluorescence yield in the light-adapted state; stomatal conductance to water vapor; thiobarbituric acid; thiobarbituric acid reactive substances; transpiration rate; triose phosphate utilization; variable and maximal fluorescence ratio; Φ(PSII); Φ(a)