TY - JOUR
T1 - Ozone stress in woody plants assessed with chlorophyll a fluorescence. A critical reassessment of existing data
AU - Bussotti, Filippo
AU - Desotgiu, Rosanna
AU - Cascio, Chiara
AU - Pollastrini, Martina
AU - Gravano, Elisabetta
AU - Gerosa, Giacomo Alessandro
AU - Marzuoli, Riccardo
AU - Nali, Cristina
AU - Lorenzini, Giacomo
AU - Salvatori, Elisabetta
AU - Manes, Fausto
AU - Schaub, Marcus
AU - Strasser, Reto J.
PY - 2011
Y1 - 2011
N2 - This paper proposes an overall reassessment of results from fluorescence transient (FT) and modulated
fluorescence (MF) analysis on tree species subjected to treatment with ozone. Findings from literature
and open-top chamber experiments were used in this review, in order to identify damage mechanisms
and repair/avoidance strategies. Main results are summarised below.
(i) The most widely used parameter to assess the response to ozone treatment was the quantum yield of
primary photochemistry in the dark-adapted state (ϕPo, or FV/FM). This parameter proved to be very
stable in stress and control conditions. Ozone-induced stress – and the related loss of photosynthetic
efficiency and performance – was characterized by the change occurring in all parameters connected
with the controlled dissipation: reduction of FM, FV/FM, RC/CS0 (in the fluorescence transient analysis)
andNPQ(in theMFanalysis). This can be considered as a down-regulationmechanismaimed at lowering
the electron supply as a consequence of a reduced demand from the Calvin cycle.
(ii) The FT analysis revealed a change in the I–P region shape, indicating that events beyond PSI are affected.
These events include a lesser density of PSI itself and the compromised ability of the end acceptors of
electrons (ferredoxine, NADP+) and RuBP to manage effectively the flux of electrons. This behaviour
may create an imbalance between electrons sent by the electron transport chain and those reaching
the acceptors beyond PSI. Free electrons (those coming from PSI, but that do not reach the end acceptors)
can activate the oxygen from fundamental to excited status, with production of ROS (Reactive Oxygen
Species), thus inducing photo-oxidation processes of the cellular content.
(iii) In many cases a temporarily enhanced efficiency of electron trapping and transport (expressed by the
parameters FV/FM, ET/TR, PIABS, pQ) in PSII system has been observed. That efficiency has been connected
to the triggering of repair processes, but when it is connected to a reduced end acceptor capacity in
combination with reduced Calvin cycle energy demand lead to over-excitation of the photosynthetic
apparatus and initiates response towards visible foliar injury.
(iv) The behaviour of F0 can help us distinguish between different response strategies. The increase of F0
observed in some ozone-treated plant species is considered an expression of irreversible damage in PSII,
whereas lowered values of this parameter may indicate the activation of PSII in the cells surrounding
the damaged one, as part of a compensative process.
Future directions for the research in this field concern: (i) the possibility to combine fluorescence
parameters with carbon assimilation and growth to support the study on critical levels and (ii) the analysis
of the events concerning the activity of PSI and the events leading to the fixation of CO2, by using
innovative technologies.
AB - This paper proposes an overall reassessment of results from fluorescence transient (FT) and modulated
fluorescence (MF) analysis on tree species subjected to treatment with ozone. Findings from literature
and open-top chamber experiments were used in this review, in order to identify damage mechanisms
and repair/avoidance strategies. Main results are summarised below.
(i) The most widely used parameter to assess the response to ozone treatment was the quantum yield of
primary photochemistry in the dark-adapted state (ϕPo, or FV/FM). This parameter proved to be very
stable in stress and control conditions. Ozone-induced stress – and the related loss of photosynthetic
efficiency and performance – was characterized by the change occurring in all parameters connected
with the controlled dissipation: reduction of FM, FV/FM, RC/CS0 (in the fluorescence transient analysis)
andNPQ(in theMFanalysis). This can be considered as a down-regulationmechanismaimed at lowering
the electron supply as a consequence of a reduced demand from the Calvin cycle.
(ii) The FT analysis revealed a change in the I–P region shape, indicating that events beyond PSI are affected.
These events include a lesser density of PSI itself and the compromised ability of the end acceptors of
electrons (ferredoxine, NADP+) and RuBP to manage effectively the flux of electrons. This behaviour
may create an imbalance between electrons sent by the electron transport chain and those reaching
the acceptors beyond PSI. Free electrons (those coming from PSI, but that do not reach the end acceptors)
can activate the oxygen from fundamental to excited status, with production of ROS (Reactive Oxygen
Species), thus inducing photo-oxidation processes of the cellular content.
(iii) In many cases a temporarily enhanced efficiency of electron trapping and transport (expressed by the
parameters FV/FM, ET/TR, PIABS, pQ) in PSII system has been observed. That efficiency has been connected
to the triggering of repair processes, but when it is connected to a reduced end acceptor capacity in
combination with reduced Calvin cycle energy demand lead to over-excitation of the photosynthetic
apparatus and initiates response towards visible foliar injury.
(iv) The behaviour of F0 can help us distinguish between different response strategies. The increase of F0
observed in some ozone-treated plant species is considered an expression of irreversible damage in PSII,
whereas lowered values of this parameter may indicate the activation of PSII in the cells surrounding
the damaged one, as part of a compensative process.
Future directions for the research in this field concern: (i) the possibility to combine fluorescence
parameters with carbon assimilation and growth to support the study on critical levels and (ii) the analysis
of the events concerning the activity of PSI and the events leading to the fixation of CO2, by using
innovative technologies.
KW - OKJIP-transient
KW - Open-top chambers
KW - Performance index
KW - Quantum yeald efficiency
KW - Reaction centres
KW - chlorophyll a fluorescence
KW - visible foliar symptoms
KW - OKJIP-transient
KW - Open-top chambers
KW - Performance index
KW - Quantum yeald efficiency
KW - Reaction centres
KW - chlorophyll a fluorescence
KW - visible foliar symptoms
UR - http://hdl.handle.net/10807/28888
U2 - 10.1016/j.envexpbot.2010.10.022
DO - 10.1016/j.envexpbot.2010.10.022
M3 - Article
SN - 0098-8472
VL - 2011
SP - 19
EP - 30
JO - Environmental and Experimental Botany
JF - Environmental and Experimental Botany
ER -