Responses to ozone on Populus “Oxford” clone in an open top chamber experiment assessed before sunrise and in full sunlight [2013] (original) (raw)
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Photosynthetica, 2013
The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populus maximowiczii Henry X P. × berolinensis Dippel -Oxford clone) in an open top chamber experiment carried out at the Curno facilities (Northern Italy). Chlorophyll (Chl) a fluorescence parameters (from both modulated and direct fluorescence) were assessed at different hours of the day (predawn, morning, midday, afternoon, and evening), from June to August 2008. This paper compares the results from predawn (PD, before sunrise) and afternoon (AN, in full sunlight) measurements, in order to evaluate the role of high sunlight as a factor influencing responses to ozone stress. Sunlight affected the maximum quantum yield of primary photochemistry (decrease of F v /F m ) thus indicating photoinhibition. The effective quantum yield (Φ PSII ) and the photochemical quenching (q P ) were enhanced in the afternoon with respect to the predawn, whereas the nonphotochemical quenching (NPQ) was reduced. The effect of ozone was detected with fluorescence on well watered plants in the first week of July, before the onset of visible symptoms. As far as F v /F m are concerned, the differences between ozone-treated and control plants were statistically significant in the predawn, but not in the afternoon. Ozone exerted only minor effects on drought exposed plants because of the reduced stomatal ozone uptake, but effects on the IP phase of the fluorescence transient were observed also in drought-stressed plants. Abbreviations: ABS -absorption energy flux; AN -afternoon; AOT40 -accumulated ozone above the threshold of 40 ppb; CF -charcoal filtered chambers; D -nonwatered plants (dry); DM -dry mass; ET -energy flux for electron; F 0 -minimal fluorescence of the dark-adapted state; F 0 ' -minimal fluorescence of the light-adapted state; F m -maximal fluorescence of the darkadapted state; F m ' -maximal fluorescence of the light-adapted state; FM -fresh mass; F v -total variable fluorescence (F m -F 0 ); F v /F m (= φ Po ) -maximum quantum yield of primary photochemistry in the dark-adapted state; F v ' /F m ' -PSII maximum efficiency in the light-adapted state; g s -stomatal conductance to water vapour; IP phase -[ΔV IP = 1 -V I ] -indicates the amplitude of the IP phase, i.e. the efficiency of electron transport around the PSI to reduce the final acceptors of the electron transport chain; J step -[Ψ Eo = 1 -V J ], expresses the efficiency with which a trapped exciton can move an electron into the electron transport chain from Q A to the intersystem electron acceptors; K band -relative variable fluorescence at 300 μs; L band -relative variable fluorescence at 100 μs; NF -not filtered chambers; NPQ -nonphotochemical quenching; OEC -oxygen-evolving complex; OTC -open top chamber; PAR -photosynthetically active radiation; PD -predawn; PI tot -Performance Index total, i.e. the performance index for energy conservation from photons absorbed by PSII to the reduction flux of PSI end acceptors; P N -net photosynthetic rate; PSI -photosystem I; PSII -photosystem II; q P -photochemical quenching; R -rainfall; RC -reaction center; RE -energy flux for the reduction of end acceptors; RH -relative humidity; RWC -relative water content; SM -satured fresh mass; T -temperature; TR -trapping capacity; V t -variable fluorescence at time t; W -well watered plants; Φ PSII -actual quantum yield of PSII, or PSII operating efficiency; Ψ w -water potential.
1995
A newly developed portable chlorophyll fluorometer in combination with a special leaf clip holder was used for assessing photosynthetic activity of attached sun leaves of Fagus sylvatica and Cucurbita pepo under field conditions. During diurnal time courses, fluorescence yield, photosynthetic photon flux density (PPFD) incident on the leaf plane, and leaf temperature were measured and quantum efficiency of photosystem II (PS II), apparent relative electron transport rates, and non-photochemical fluorescence quenching (NPQ) calculated. In both species, quantum efficiency followed closely the incident PPFD and no hysteresis could be observed during the day. Apparent electron transport rate showed light saturation above a PPFD of 700 ~tmol m -2 s -1 in F. sylvatica, while in C. pepo no saturation was visible up to 1400 gmol m -2 s 1. NPQ was closely correlated to excessive PPFD calculated from the PS II quantum yield. Maximal NPQ observed was 3.3. Although the beech leaf was exposed for a considerable time to PPFD values of 1400-1500 pmol m -2 s 1 and leaf temperatures between 30 and 35~ no obvious signs for sustained photodamage could be observed. The data demonstrate the potential of chlorophyll fluorescence measurements to analyse photosynthetic performance under field conditions with minimal disturbance of the plant. Potential error sources due to the geometry of the leaf clip holder used are discussed.
Effect of sequences of ozone and nitrogen dioxide on chlorophyll fluorescence in radish
Ozone (O 3 ) is the most important of the phytotoxic gaseous air pollutants. It causes substantial decreases in crop yields worldwide and bears adverse effects on vegetation in general. On the other hand, nitrogen dioxide (NO 2 ) is the air pollutant most likely to be associated with O 3 because it is a precursor of O 3 . The objective of this study was to determine the effects of sequential exposures to nitrogen dioxide (NO 2 ) and ozone (O 3 ) on chlorophyll fluorescence in radish, Raphanus sativus L. Radish plants were exposed daily to O 3 or NO 2 , or sequences of the two gases. The exposure profiles for both gases approximated sine waves with peak concentrations of 120 ppb (parts per billion by volume, nl l -1 ). In the case of O 3 , this is close to the reported threshold for adverse effects; while for NO 2 it is below the reported threshold. The sequences involved different combinations of exposures to NO 2 from 06:00 to 10:00h and/or 18:00 to 22:00hr and O 3 from 10:00 to 18:00hr. Relative to the control, early and early + late NO 2 resulted in stimulations of quantum yield (Y) and photochemical quenching (qP), with late NO 2 resulting in little or no change. In contrast, early, late and early + late NO 2 in combination with O 3 resulted in progressive reductions in these variables. The overall effect of O 3 treatment was to stimulate quantum yield and qP, both of which are indicative of increased photochemistry. Late NO 2 exposures caused no significant effects relative to the control. However, late NO 2 failed to result in a significant stimulation of photochemistry in the chloroplast, but caused significant residual increases in non-photochemical quenching (qN) during the middle of the day, responses which imply increased photo-protection capacity. Stimulation of quantum yield and photochemical quenching by O 3 , O 3 + late NO 2 , O 3 + early NO 2 , early NO 2 and late + early NO 2 implies that CO 2 -fixation was limited by processes at PSII. However, apart from the early NO 2 related stimulation of qN, all exposures involving O 3 led to a decrease in qN implying inability to regulate photosnynthesis resulting from changes in the thylakoid membrane. In the case of NPQ, all exposures including O 3, decreased this parameter suggesting impaired proper functioning of the xanthophyll cycle associated with the light-harvesting complex of photosystem II.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2000
O 2 evolution from single turnover flashes of up to 96 Wmol absorbed quanta m 32 and from multiple turnover pulses of 8.6 and 38.6 ms duration and 12 800 and 850 Wmol absorbed quanta m 32 s 31 intensity, respectively, was measured in sunflower leaves with the help of zirconium O 2 analyser. O 2 evolution from one flash could be measured with 1% accuracy on the background of 10^50 Wmol O 2 mol 31 . Before the measurements leaves were pre-adapted either at 30^60 or 1700 Wmol quanta m 32 s 31 to induce different non-photochemical excitation quenching (q N ). Short (1 min) exposures at the high light that created only energy-dependent, q E type quenching, caused no changes in the O 2 yield from saturating flashes or pulses that could be related to the q E quenching, but the yield from low intensity flashes and pulses decreased considerably. Long 30^60min exposures at the high light induced a reversible inhibitory, q I type quenching that decreased the O 2 yield from both, saturating and limiting flashes and pulses (but more from the limiting ones), which reversed within 15 min under the low light. The results are in agreement with the notion that q E is caused by a quenching process in the PSII antenna and no changes occur in the PSII centres, but the reversible (15^30 min) q I quenching is accompanied by inactivation of a part of PSII centres. ß 0005-2728 / 00 / $^see front matter ß 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 5 -2 7 2 8 ( 0 0 ) 0 0 1 5 5 -9
Photosynthetica, 2020
An overview is given of several studies on the fast chlorophyll (Chl) a fluorescence (OJIP) transient carried out in the laboratory of Reto Strasser between 2001 and 2009. At the beginning of this period the HandyPEA and PEA-Senior instruments were introduced by Reto Strasser and Hansatech Instruments Ltd. (UK) that gave a lot of experimental flexibility compared to the experiments that were feasible in the preceding years. These technical innovations, including the combination of 820-nm transmission measurements (for the determination of the P700 and PC redox states) and Chl a fluorescence [originating from photosystem II (PSII)], enabled us to establish the effects of electron flow through and at the acceptor side of photosystem I during a dark-to-light transition on fluorescence induction in leaves. These instruments further allowed us to show biological variability between various photosynthetic organisms and how several chemical treatments could modify the Chl a fluorescence kinetics. We also obtained new information on the effect of the inhibitor DCMU [3-(3ꞌ,4ꞌ-dichlorophenyl)-1,1-dimethylurea] on Chl a fluorescence induction. In addition, the effects of heat stress on electron flow through PSII and the entire electron transport chain were investigated in detail. The article also reflects how our perception and interpretation of the OJIP kinetics changed over time.
Rapid light curves: a new fluorescence method to assess the state of the photosynthetic apparatus
Photosynthesis Research, 1999
Photosynthetic electron transport rates (ETR), calculated from chlorophyll fluorescence parameters, were compared in long term light and dark adapted as well as photoinhibited Pisum sativum leaves using a novel chlorophyll fluorescence method and a new instrument: rapid light curves (RLC) generated with the MINI-PAM. RLCs are plots of ETRs versus actinic irradiances applied for 10 s. Large changes in maximum electron transport rates (ETR max ) were observed when leaves were shifted from dark to moderate light, or from dark to photoinhibitory light and vice versa. Maximum ETRs were very low following long term dark adaptation, but increased to maximum levels within 8 to 15 minutes of illumination. It took more than 3 hours, however, to return irradiance-exposed leaves to the fully dark adapted state. Quenching analysis of RLCs revealed large q E development in long-term dark adapted leaves accounting for the low ETRs. Leaves photoinhibited for 3 hours had similarly reduced ETRs. In these leaves, however, q I was largely responsible for this reduction. Actinic irradiance exposures and saturating flashes affected leaves with different irradiance histories differently.
Physiologia Plantarum, 2007
This paper reports the findings of an open-top chamber experiment carried out in northern Italy (Forest nursery at Curno), during the 2004 and 2005 growth seasons, on Fagus sylvatica and Quercus robur seedlings and on Populus nigra cuttings, in order to test their photosynthesis response to ambient ozone. The experimental protocols were non-filtered air (NF), charcoal-filtered air (CF) and open air (OA). Tests performed included morphological features of leaves; development of foliar symptoms; chlorophyll content, determined by nondestructive means; chlorophyll fluorescence (direct fluorescence and JIP test) and gas exchanges and net photosynthesis (P N ). Main findings were as follows:
Functional Plant Biology, 2017
The prototype light-induced fluorescence transient (LIFT) instrument provides continuous, minimally intrusive, high time resolution (~2 s) assessment of photosynthetic performance in terrestrial plants from up to 2 m. It induces a chlorophyll fluorescence transient by a series of short flashes in a saturation sequence (180 1μs flashlets inμs) to achieve near-full reduction of the primary acceptor QA, followed by a relaxation sequence (RQA; 90 flashlets at exponentially increasing intervals over ~30 ms) to observe kinetics of QA reoxidation. When fitted by the fast repetition rate (FRR) model (Kolber et al. 1998) the QA flash of LIFT/ FRR gives smaller values for FmQA from dark adapted leaves than FmPAM from pulse amplitude modulated (PAM) assays. The ratio FmQA/FmPAM resembles the ratio of fluorescence yield at the J/P phases of the classical O-J-I-P transient and we conclude that the difference simply is due to the levels of PQ pool reduction induced by the two techniques. In a strong PAM-analogous WL pulse in the dark monitored by the QA flash of LIFT/FRR φPSIIWL ≈ φPSIIPAM. The QA flash also tracks PQ pool reduction as well as the associated responses of ETR QA → PQ and PQ → PSI, the relative functional (σPSII) and optical absorption (aPSII) cross-sections of PSII in situ with a time resolution of ~2 s as they relax after the pulse. It is impractical to deliver strong WL pulses at a distance in the field but a longer PQ flash from LIFT/FRR also achieves full reduction of PQ pool and delivers φPSIIPQ ≈ φPSIIPAM to obtain PAM-equivalent estimates of ETR and NPQ at a distance. In situ values of σPSII and aPSII from the QA flash with smaller antenna barley (chlorina-f2) and Arabidopsis mutants (asLhcb2-12, ch1-3 Lhcb5) are proportionally similar to those previously reported from in vitro assays. These direct measurements are further validated by changes in antenna size in response to growth irradiance. We illustrate how the QA flash facilitates our understanding of photosynthetic regulation during sun flecks in natural environments at a distance, with a time resolution of a few seconds.