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1.
Comparison of photosynthetic damage from arthropod herbivory and pathogen infection in understory hardwood saplings 总被引:2,自引:0,他引:2
Aldea M Hamilton JG Resti JP Zangerl AR Berenbaum MR Frank TD Delucia EH 《Oecologia》2006,149(2):221-232
Arthropods and pathogens damage leaves in natural ecosystems and may reduce photosynthesis at some distance away from directly injured tissue. We quantified the indirect effects of naturally occurring biotic damage on leaf-level photosystem II operating efficiency (ΦPSII) of 11 understory hardwood tree species using chlorophyll fluorescence and thermal imaging. Maps of fluorescence parameters and leaf temperature were stacked for each leaf and analyzed using a multivariate method adapted from the field of quantitative remote sensing. Two tree species, Quercus velutina and Cercis canadensis, grew in plots exposed to ambient and elevated atmospheric CO2 and were infected with Phyllosticta fungus, providing a limited opportunity to examine the potential interaction of this element of global change and biotic damage on photosynthesis. Areas surrounding damage had depressed ΦPSII and increased down-regulation of PSII, and there was no evidence of compensation in the remaining tissue. The depression of ΦPSII caused by fungal infections and galls extended >2.5 times further from the visible damage and was ∼40% more depressed than chewing damage. Areas of depressed ΦPSII around fungal infections on oaks growing in elevated CO2 were more than 5 times larger than those grown in ambient conditions, suggesting that this element of global change may influence the indirect effects of biotic damage on photosynthesis. For a single Q. velutina sapling, the area of reduced ΦPSII was equal to the total area directly damaged by insects and fungi. Thus, estimates based only on the direct effect of biotic agents may greatly underestimate their actual impact on photosynthesis. 相似文献
2.
Miscanthus × giganteus (Greef & Deuter ex Hodkinson & Renvoize) is unique among C4 species in its remarkable ability to maintain high photosynthetic productivity at low temperature, by contrast to the related C4 NADP-malic enzyme-type species Zea mays L. In order to determine the in vivo physiological basis of this difference in photosynthesis, water vapor and CO2 exchange and modulated chlorophyll fluorescence were simultaneously monitored on attached leaf segments from plants grown and measured at 25/20°C or 14/11°C (day/night temperature). Analysis of the response of photosynthesis to internal CO2 concentration suggested that ribulose bisphosphate carboxylase/oxygenase (Rubisco) and/or pyruvate orthophosphate dikinase (PPDK) play a more important role in determining the response to low temperature than does phosphoenolpyruvate carboxylase (PEPc). For both species at both temperatures, the linear relationship between operating efficiency of whole-chain electron transport through photosystem II (PSII) and the efficiency of CO2 assimilation (CO2) was unchanged and had a zero intercept, suggesting the absence of non-photosynthetic electron sinks. The major limitation at low temperature could not be solely at Rubisco or at any other point in the Calvin cycle, since this would have increased leakage of CO2 to the mesophyll and increased PSII/CO2. This in vivo analysis suggested that maintenance of high photosynthetic rates in M. × giganteus at low temperature, in contrast to Z. mays, is most likely the result of different properties of Rubisco and/or PPDK, reduced susceptibility to photoinhibition, and the ability to maintain high levels of leaf absorptance during growth at low temperature. 相似文献
3.
Z. -M. Ge X. Zhou S. Kellomäki K. -Y. Wang H. Peltola P. J. Martikainen 《Photosynthetica》2011,49(2):172-184
The effects of elevated growth temperature (ambient + 3.5°C) and CO2 (700 μmol mol−1) on leaf photosynthesis, pigments and chlorophyll fluorescence of a boreal perennial grass (Phalaris arundinacea L.) under different water regimes (well watered to water shortage) were investigated. Layer-specific measurements were conducted
on the top (younger leaf) and low (older leaf) canopy positions of the plants after anthesis. During the early development
stages, elevated temperature enhanced the maximum rate of photosynthesis (P
max) of the top layer leaves and the aboveground biomass, which resulted in earlier senescence and lower photosynthesis and biomass
at the later periods. At the stage of plant maturity, the content of chlorophyll (Chl), leaf nitrogen (NL), and light response of effective photochemical efficiency (ΦPSII) and electron transport rate (ETR) was significantly lower under elevated temperature than ambient temperature in leaves
at both layers. CO2 enrichment enhanced the photosynthesis but led to a decline of NL and Chl content, as well as lower fluorescence parameters of ΦPSII and ETR in leaves at both layers. In addition, the down-regulation by CO2 elevation was significant at the low canopy position. Regardless of climate treatment, the water shortage had a strongly
negative effect on the photosynthesis, biomass growth, and fluorescence parameters, particularly in the leaves from the low
canopy position. Elevated temperature exacerbated the impact of water shortage, while CO2 enrichment slightly alleviated the drought-induced adverse effects on P
max. We suggest that the light response of ΦPSII and ETR, being more sensitive to leaf-age classes, reflect the photosynthetic responses to climatic treatments and drought
stress better than the fluorescence parameters under dark adaptation. 相似文献
4.
Helena Kyseláková Jitka Prokopová Jan Nauš Ond?ej Novák Milan Navrátil Dana Šafá?ová Martina Špundová Petr Ilík 《Plant Physiology and Biochemistry》2011,49(11):1279-1289
We have investigated photosynthetic changes of fully expanded pea leaves infected systemically by pea enation mosaic virus (PEMV) that often attacks legumes particularly in northern temperate regions. A typical compatible virus–host interaction was monitored during 40 post-inoculation days (dpi). An initial PEMV-induced decrease in photosynthetic CO2 assimilation was detected at 15 dpi, when the virus appeared in the measured leaves. This decrease was not induced by stomata closure and corresponded with a decrease in the efficiency of photosystem II photochemistry (ΦPSII). Despite of a slight impairment of oxygen evolution at this stage, PSII function was not primarily responsible for the decrease in ΦPSII. Chlorophyll fluorescence imaging revealed that ΦPSII started to decrease from the leaf tip to the base. More pronounced symptoms of PEMV disease appeared at later stages, when a typical mosaic and enations appeared in the infected leaves and oxidative damage of cell membranes was detected. From 30 dpi, a degradation of photosynthetic pigments accelerated, stomata were closing and corresponding pronounced decline in CO2 assimilation was observed. A concomitant photoprotective responses, i.e. an increase in non-photochemical quenching and accumulation of de-epoxidized xanthophylls, were also detected. Interestingly, alternative electron sinks in chloroplasts were not stimulated by PEMV infection, which is in contradiction to earlier reports dealing with virus-induced plant stresses. The presented results show that the PEMV-induced alterations in mature pea leaves accelerated leaf senescence during which a decrease in ΦPSII took place in coordinated manner with an inhibition of CO2 assimilation. 相似文献
5.
The objective of this study was to elucidate the genetic relationship between the specific leaf area (SLA) and the photosynthetic
performance of maize (Zea mays L.) as dependent on growth temperature. Three sets of genotypes: (i) 19 S5 inbred lines, divergently selected for high or low operating efficiency of photosystem II (ΦPSII) at low temperature, (ii) a population of 226 F2:3 families from the cross of ETH-DL3 × ETH-DH7, and (iii) a population of 168 F2:4 families from the cross of Lo964 × Lo1016 were tested at low (15/13 °C day/night) or at optimal (25/22 °C day/night) temperature.
The latter cross was originally developed to study QTLs for root traits. At 15/13 °C the groups of S5 inbred lines selected for high or low ΦPSII differed significantly for all the measured traits, while at optimal temperature the groups differed only with regard to
leaf greenness (SPAD). At low temperature, the SLA of these inbred lines was negatively correlated with ΦPSII (r = − 0.56, p < 0.05) and SPAD (r = − 0.80, p < 0.001). This negative relationship was confirmed by mapping quantitative trait loci (QTL) in the two mapping populations.
A co-location of three QTLs for SLA with QTLs for photosynthesis-related traits was detected in both populations at 15/13 °C,
while co-location was not detected at 25/22 °C. The co-selection of SLA and ΦPSII in the inbred lines and the co-location of QTL for SLA, SPAD, and ΦPSII at 15/13 °C in the QTL populations strongly supports pleiotropy. There was no evidence that selecting for high ΦPSII at low temperature leads to a constitutively altered SLA. 相似文献
6.
7.
S. Trachsel R. Messmer P. Stamp N. Ruta A. Hund 《Molecular breeding : new strategies in plant improvement》2010,25(1):91-103
A strong photosynthetic performance and rapid leaf development, are important indicators of vigorous early growth. The aim
of this study was to (1) evaluate the tropical maize (Zea mays L.) inbred lines CML444 and SC-Malawi for their photosynthetic performance at different growth stages and (2) assess quantitative
trait loci (QTL) of photosynthesis-related traits in their 236 recombinant inbred lines at the heterotrophic growth stage.
CML444 had a higher leaf chlorophyll (SPAD) content than SC-Malawi. Ten QTLs were found for the quantum efficiency of photosystem
II (ΦPSII; four), SPAD (three) and the specific leaf area (SLA; three). The relevance of seedling QTLs for ΦPSII, SPAD and SLA for yield formation is emphasized by seven collocations (bins 5.01, 7.03, 8.05) with QTLs for kernel number
and grain yield under field conditions. QTLs for SPAD at the V2 and at the reproductive stage did not collocate, indicating
differences in the genetic control of SPAD at different growth stages. Knowing which loci affect SLA, SPAD and ΦPSII simultaneously and which do not will help to optimize light harvest by the canopy. 相似文献
8.
In order to clarify the relationship between chill-induced disturbance in photosynthetic, respiratory electron transport and
the metabolism of reactive oxygen species (ROS), leaf gas exchange, chlorophyll fluorescence quenching, respiration, and activities
of superoxide dismutase (SOD) and ascorbate peroxidase (APX) were investigated in chloroplasts and mitochondria of cucumber
(Cucumis sativus) leaves subjected to a chill (8 °C) for 4 d. Chilling decreased net photosynthetic rate (P
N) and quantum efficiency of photosystem 2 (ΦPS2), but increased the ratio of ΦPS2 to the quantum efficiency of CO2 fixation (ΦCO2) and non-photochemical quenching (NPQ) in cucumber leaves. While chilling inhibited the activity of cytochrome respiration
pathway, it induced an increase of alternative respiration pathway activity and the reduction level of Q-pool. Chilling also
significantly increased O2
• production rate, H2O2 content, and SOD and APX activities in chloroplasts and mitochondria. There was a more significant increase in SOD and APX
activities in chloroplasts than in mitochondria with the increase of membrane-bound Fe-SOD and tAPX in chloroplasts being
more significant than other isoenzymes. Taken together, chilling inhibited P
N and cytochrome respiratory pathway but enhanced the photosynthetic electron flux to O2 and over-reduction of respiratory electron transport chain, resulting in ROS accumulation in cucumber leaves. Meanwhile,
chilling resulted in an enhancement of the protective mechanisms such as thermal dissipation, alternative respiratory pathway,
and ROS-scavenging mechanisms (SODs and APXs) in chloroplasts and mitochondria. 相似文献
9.
Nan Liu Zhi-Fang Lin Anna Van Devender Gui-Zhu Lin Chang-Lian Peng Xiao-Ping Pan Shao-Wei Chen Qun Gu 《Plant Growth Regulation》2009,58(1):73-84
Pigment combinations are regulated during leaf ontogenesis. To better understand pigment function, alterations in chlorophyll,
carotenoid and anthocyanin concentrations were investigated during different leaf development stages in six subtropical landscape
plants, namely Ixora chinensis Lam, Camellia japonica Linn, Eugenia oleina Wight, Mangifera indica L., Osmanthus fragrans Lowr and Saraca dives Pierre. High concentrations of anthocyanin were associated with reduced chlorophyll in juvenile leaves. As leaves developed,
the photosynthetic pigments (chlorophyll and carotenoid) of all six species increased while anthocyanin concentration declined.
Chlorophyll fluorescence imaging of ΦPSII (effective quantum yield of PSII) and of NPQ (non-photochemical fluorescence quenching) and determination of electron transport
rate-rapid light curve (RLC) showed that maximum ETR (leaf electron transport rate), ΦPSII and the saturation point in RLC increased during leaf development but declined as they aged. Juvenile leaves displayed higher
values of NPQ and Car/Chl ratios than leaves at other developmental stages. Leaf reflectance spectra (400–800 nm) were measured
to provide an in vivo non-destructive assessment of pigments in leaves during ontogenesis. Four reflectance indices, related
to pigment characters, were compared with data obtained quantitatively from biochemical analysis. The results showed that
the ARI (anthocyanin reflectance index) was linearly correlated to anthocyanin concentration in juvenile leaves, while a positive
correlation of Chl NDI (chlorophyll normalized difference vegetation index) to chlorophyll a concentration was species dependent. Photosynthetic reflectance index was not closely related to Car/Chl ratio, while a structural-independent
pigment index was not greatly altered by leaf development or species. Accordingly, it is suggested that the high concentration
of anthocyanin, higher NPQ and Car/Chl ratio in juvenile leaves are important functional responses to cope with high radiation
when the photosynthetic apparatus is not fully developed. Another two leaf reflectance indices, ARI and Chl NDI, are valuable
for in vivo pigment evaluation during leaf development. 相似文献
10.
Chlorophyll (Chl) fluorescence of warm day/cool night temperature exposed Phalaenopsis plants was measured hourly during 48 h to study the simultaneous temperature and irradiance response of the photosynthetic
physiology. The daily pattern of fluorescence kinetics showed abrupt changes of photochemical quenching (qP), non-photochemical quenching (NPQ) and quantum yield of photosystem II electron transport (ΦPSII) upon transition from day to night and vice versa. During the day, the course of ΦPSII and NPQ was related to the air temperature pattern, while maximum quantum efficiency of PSII photochemistry (Fv/Fm) revealed a rather light dependent response. Information on these daily dynamics in fluorescence kinetics is important with
respect to meaningful data collection and interpretation. 相似文献
11.
Photoinhibitory damage is modulated by the rate of photosynthesis and by the photosystem II light-harvesting chlorophyll antenna size 总被引:12,自引:0,他引:12
We investigated the effect of photosynthetic electron transport and of the photosystem II (PSII) chlorophyll (Chl) antenna
size on the rate of PSII photoinhibitory damage. To modulate the rate of photosynthesis and the light-harvesting capacity
in the unicellular chlorophyte Dunaliella salina Teod., we varied the amount of inorganic carbon in the culture medium. Cells were grown under high irradiance either with
a limiting supply of inorganic carbon, provided by an initial concentration of 25 mM NaHCO3, or with supplemental CO2 bubbled in the form of 3% CO2 in air. The NaHCO3-grown cells displayed slow rates of photosynthesis and had a small PSII light-harvesting Chl antenna size (60 Chl molecules).
The half-time of PSII photodamage was 40 min. When switched to supplemental CO2 conditions, the rate of photodamage was retarded to a t1/2 = 70 min. Conversely, CO2-supplemented cells displayed faster rates of photosynthesis and a larger PSII light-harvesting Chl antenna size (500 Chl
molecules). They also showed a rate of photodamage with t1/2 = 40 min. When depleted of CO2, the rate of photodamage was accelerated (t1/2 = 20 min). These results indicate that the in-vivo susceptibility to photodamage is modulated by the rate of forward electron
transport through PSII. Moreover, a large Chl antenna size enhances the rate of light absorption and photodamage and, therefore,
counters the mitigating effect of forward electron transport. We propose that under steady-state photosynthesis, the rate
of light absorption (determined by incident light intensity and PS Chl antenna size) and the rate of forward electron transport
(determined by CO2 availability) modulate the oxidation/reduction state of the primary PSII acceptor QA, which in turn defines the low/high probability for photodamage in the PSII reaction center.
Received: 14 August 1997 / Accepted: 26 September 1997 相似文献
12.
The mechanisms contributing to photosynthetic control of electron transport by carbon assimilation in leaves 总被引:17,自引:0,他引:17
Christine Foyer Robert Furbank Jeremy Harbinson Peter Horton 《Photosynthesis research》1990,25(2):83-100
Photosynthetic control describes the processes that serve to modify chloroplast membrane reactions in order to co-ordinate the synthesis of ATP and NADPH with the rate at which these metabolites can be used in carbon metabolism. At low irradiance, optimisation of the use of excitation energy is required, while at high irradiance photosynthetic control serves to dissipate excess excitation energy when the potential rate of ATP and NADPH synthesis exceed demand. The balance between pH, ATP synthesis and redox state adjusts supply to demand such that the [ATP]/[ADP] and [NADPH]/[NADP+] ratios are remarkably constant in steady-state conditions and modulation of electron transport occurs without extreme fluctuations in these pools.Abbreviations FBPase
Fructose-1,6-bisphosphatase
- PS I
Photosystem I
- PS II
Photosystem II
- Pi
inorganic phosphate
- PGA
glycerate 3-phosphate
- PQ
plastoquinone
- QA
the bound quinone electron acceptor of PS II
- qP
Photochemical quenching of chlorophyll fluorescence associated with the oxidation of QA
- qN
non-photochemical quenching of chlorophyll fluorescence
- qE
non-photochemical quenching associated with the high energy state of the membrane
- RuBP
ribulose-1,5-bisphosphate
- TP
triose phosphate
-
intrinsic quantum yield of PS II
-
quantum yield of electron transport
-
quantum yield of CO2 assimilation 相似文献
13.
The regulation of photosystem II (PSII) by light-, CO2-, and O2-dependent changes in the capacity for carbon metabolism was studied. Estimates of the rate of electron transport through PSII were made from gas-exchange data and from measurements of chlorophyll fluorescence. At subsaturating photon-flux density (PFD), the rate of electron transport was independent of O2 and CO2. Feedback on electron transport was observed under two conditions. At saturating PFD and low partial pressure of CO2, p(CO2), the rate of electron transport increased with p(CO2). However, at high p(CO2), switching from normal to low p(O2) did not affect the net rate of photosynthetic CO2 assimilation but the rate of electron-transport decreased by an amount related to the change in the rate of photorespiration. We interpret these effects as 1) regulation of ribulose-1,5-bisphosphatecarboxylase (RuBPCase, EC 4.1.1.39) activity to match the rate of electron transport at limiting PFD, 2) regulation of electron-transport rate to match the rate of RuBPCase at low p(CO2), and 3) regulation of the electron-transport rate to match the capacity for starch and sucrose synthesis at high p(CO2) and PFD. These studies provide evidence that PSII is regulated so that the capacity for electron transport is matched to the capacity for other processes required by photosynthesis, such as ribulose-bisphosphate carboxylation and starch and sucrose synthesis. We show that at least two mechanisms contribute to the regulation of PSII activity and that the relative engagement of these mechanisms varies with time following a step change in the capacity for ribulose-bisphosphate carboxylation and starch and sucrose synthesis. Finally, we take advantage of the relatively slow activation of deactivated RuBPCase in vivo to show that the activation level of this enzyme can limit the rate of electron transport as evidenced by increased feedback on PSII following a step change in p(CO2). As RuBPCase as activated, the feedback on PSII declined.Abbreviations and symbols JC
electron-transport rate calculated from CO2-assimilation measurements
- JF
electron-transport rate calculated from fluorescence parameters
- PFD
photon-flux density
- qE
energy-dependent quenching
- PSII
photosystem II
- qQ
Q-dependent quenching
- QY
quantum yield
- RuBPCase
ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39)
C.I.W. publication No. 1015 相似文献
14.
Caragana korshinskii seedlings maintain positive photosynthesis during short-term,severe drought stress 总被引:1,自引:0,他引:1
Seedling performance may determine plant distribution, especially in water-limited environments. Plants of Caragana korshinskii commonly grow in arid and semiarid areas in northwestern China, and endure water shortage in various ways, but little is
known about their performance when water shortage occurs at early growth stages. The water relations, photosynthetic activity,
chlorophyll (Chl) content and proline accumulation were determined in 1-year-old seedlings growing in a 1:1 mixture of Loess
soil and Perlite and subjected to (1) a water deficit for 20 days and (2) kept adequately watered throughout. The water deficit induced low (−6.1 MPa) predawn leaf water potentials (LWP), but did
not induce any leaf abscission. Stomatal conductance (g
s), leaf transpiration rate (E), and net photosynthetic rate (P
N) decreased immediately following the imposition of the water deficit, while the maximal photochemical efficiency of photosystem
II (PSII) (Fv/Fm) and the effective quantum yield of PSII (ΦPSII) decreased 15 days later. An early and rapid decrease in g
s, reduced E, increased Chl (a+b) loss, increased the apparent rate of photochemical transport of electrons through PSII (ETR)/P
N, as well as a gradual increase in non-photochemical quenching of fluorescence (NPQ) and proline may have contributed to preventing
ΦPSII from photodamage. C. korshinskii seedlings used a stress-tolerance strategy, with leaf maintenance providing a clear selective advantage, considering the
occasional rainfall events during the growing season. 相似文献
15.
The electron-transport machinery in photosynthetic membranes is known to be very sensitive to heat. In this study, the rate of electron transport (ETR) driven by photosystem I (PSI) and photosystem II (PSII) during heat stress in the wild-type Synechocystis sp. strain PCC 6803 (WT) and its ndh gene inactiva-tion mutants ΔndhB (M55) and ΔndhD1/ndhD2 (D1/D2) was simultaneously assessed by using the novel Dual-PAM-100 measuring system. The rate of electron transport driven by the photosystems (ETRPSs) in the WT, M55, and D1/D2 cells incubated at 30℃ and at 55℃ for 10 min was compared. Incubation at 55℃ for 10 min significantly inhibited PSII-driven ETR (ETRPSII) in the WT, M55 and D1/D2 cells, and the ex-tent of inhibition in both the M55 and D1/D2 cells was greater than that in the WT cells. Further, PSI-driven ETR (ETRPSI) was stimulated in both the WT and D1/D2 cells, and this rate was increased to a greater extent in the D1/D2 than in the WT cells. However, ETRPSI was considerably inhibited in the M55 cells. Analysis of the effect of heat stress on ETRPSs with regard to the alterations in the 2 active NDH-1 complexes in the WT, M55, and D1/D2 cells indicated that the active NDH-1 supercomplex and medi-umcomplex are essential for alleviating the heat-induced inhibition of ETRPSII and for accelerating the heat-induced stimulation of ETRPSI, respectively. Further, it is believed that these effects are most likely brought about by the electron transport mediated by each of these 2 active NDH-1 complexes. 相似文献
16.
Carbon assimilation of spinach (Spinacia oleracea L.) leaves was measured in the presence of 2000l· l–1CO2 and 2% O2 in the gas phase to suppress photorespiratory reactions and to reduce stomatal diffusion resistance. Simultaneously, membrane parameters such as modulated chlorophyll fluorescence, oxidation of P700 in the reaction centre of photosystem I, and apparent changes in absorbance at 535 nm were recorded. After light-regulated enzymes were activated at a high irradiance, illumination was changed. About 3 min later (to maintain the previous activation state of enzymes), leaves were shock-frozen and freeze-dried. Chloroplasts were isolated nonaqueously and analysed for ATP, ADP, inorganic phosphate, NADPH and NADP. Observations made under the chosen conditions differed in some important aspects from those commonly observed when leaves are illuminated in air. (i) Not only assimilation, but also the phosphorylation potential [ATP]/([ADP]·[Pi]) increased hyperbolically with irradiance towards saturation. In contrast, the ratio of NADPH to NADP did not change much as irradiances increased from low to high photon flux densities. When ATP, the phosphorylation potential and the assimilatory force, FA (the product of phosphorylation potential and NADPH/NADP ratio), were plotted against assimilation, ATP increased relatively less than assimilation, whereas the phosphorylation potential increased somewhat more steeply than assimilation did. A linear relationship existed between assimilation and FA at lower irradiances. The assimilatory force FA increased more than assimilation did when irradiances were very high. Differences from previous observations, where FA was under some conditions higher at low than at high rates of carbon assimilation, are explained by differences in flux resistances caused not only by stomatal diffusion resistance but also by differences in the activity of light-regulated enzymes, (ii) The relationship between P700 oxidation and a fast absorption change with a maximum close to 520 nm on one hand and carbon assimilation on the other hand was largely linear under the specific conditions of the experiments. A similar linear relationship existed also between the quantum efficiency of electron flow through photosystem II and the quantum efficiency of photosystem I electron transport. (iii) Whereas the increase in non-photochemical fluorescence quenching, qN, was similar to the increase in assimilation, the relationship between light scattering and assimilation was distinctly sigmoidal. Light scattering appeared to be a better indicator of control of photosystem II activity under excessive irradiation than qN. (iv) The results are discussed in relation to the relative significance of chloroplast levels of ATP and NADPH and of the assimilatory force FA in driving carbon assimilation. From the observations, the proton/electron (H+/e–) ratio of linear electron transport is suggested to be 3 and the H+/ATP ratio to be 4 in leaves. An H+/e– ratio of 3 implies the existence of an obligatory Q-cycle in leaves.Abbreviations FA
assimilatory force
- Fo
fluorescence after long dark adaptation
- Fm
maximum fluorescence level
- Fs
steady-state fluorescence
- PGA
3-phosphoglycerate
- PFD
photon flux density
- P700 (P700+)
electron-donor pigment in the reaction center of PSI (its oxidized form)
- QA
primary quinone acceptor of PSII
- qP
photochemical quenching
- qN
non-photochemical quenching
- PSII
relative quantum efficiency of energy conversation at the level of photosystem II
- PSI
relative quantum efficiency of photosystem II
This research was supported by the Sonderforschungsbereich 251 of the University of Würzburg and the Stiftung Volkswagenwerk. U.G. is a member of the Graduate College of the Julius-von-Sachs Institut für Biowissenschaften, University of Würzburg, being on leave from Tartu University, Tartu, Estonia. The authors are grateful to Prof. A. Laisk, Chair of Plant Physiology, Tartu University, for stimulating discussions. 相似文献
17.
Xing Shun Song Chun Lan Tiao Kai Shi Wei Hua Mao Joshua Otieno Ogweno Yan Hong Zhou Jing Quan Yu 《Plant Growth Regulation》2006,49(1):85-93
In order to clarify the response of antioxidant systems in various cellular organelles to photo-oxidative stress, the activities
of superoxide dismutase (SOD) and enzymes of the ascorbate–glutathione (AsA-GSH) cycle were investigated in chloroplasts,
mitochondria and cytosol of cucumber leaves subjected to methyl viologen (MV) treatment. Photo-oxidation by MV resulted in
significant reductions in net photosynthetic rate (Pn) and increases in the ratio of the quantum efficiency of photosystem
II (PSII),
ΦPSII to that of the quantum efficiency of CO2 fixation (ΦCO2), followed by increased activities of SOD, and a general increase of AsA-GSH cycle enzymes in chloroplasts, mitochondria
and cytosol. These increases were however, most significant in chloroplasts. There were also significant increases in dehydroascorbate
(DHA), reduced glutathione (GSH), and oxidized glutathione (GSSG) except that the content of ascorbate (AsA) in chloroplasts
and cytosol was slightly decreased and little effected, respectively. However, GSSG in mitochondria and GSH in cytosol were
little influenced by the MV treatment. The activity of ascorbate oxidase (AO) in these organelles was independent of the MV
treatment while the activity of l-galactono-1,4- lactone dehydrogenase (GLDH) in mitochondria was slightly inhibited by MV treatment. These results indicate
that disturbance of electron transport in chloroplasts by MV influenced the metabolism of whole cell by a crosstalk signaling
system and that the AsA-GSH cycle played a primary role in sustaining the levels of AsA. 相似文献
18.
Chang-Ming Zhao Gen-Xuan Wang Xiao-Ping Wei Jian-Ming Deng Dong-Liang Cheng 《Trees - Structure and Function》2007,21(1):55-63
Physiological and photosynthetic responses were investigated at three different depths of groundwater (DGW: 1.4, 2.4, and
3.4 m) in Elaeagnus angustifolia L., a locally adapted tree to the arid region in northwest China. Predawn leaf water potential and chlorophyll content declined
gradually with the increasing DGW, whereas there was little effect on predawn variable-to-maximum chlorophyll fluorescence
ratio F
v/F
m and leaf carotenoid compositions (xanthophyll cycle pool, neoxanthin, lutein, and β-carotene). Net photosynthetic rate (P
n), quantum yield of PSII electron transport (ΦPSII), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) declined obviously; however, P
n decreased more than ΦPSII at deeper DGW. The photoinhibition of PSII at all three DGW occurred at midday in summer and increased as DGW increased.
The ΔpH-dependent thermal dissipation and the level of de-epoxidation of the xanthophyll cycle at all three DGW reached their
maxima at midday with the increase of light intensity. However, the fraction of functional PSII and light intensity at deeper
DGW (2.4, 3.4 m) showed a negative correlation. This correlation suggested that most of violaxanthin was converted into zeaxanthin
at midday, and the reversible inactivation of partial PSII reaction centers took place at deeper DGW. These results together
suggest that both the xanthophyll cycle-dependent thermal dissipation and the reversible inactivation of partial PSII might
have played important roles in avoiding the excess light-induced energy damage in leaves of this tree species at deeper DGW. 相似文献
19.
The mechanisms of capsicum growth in response to differential light availabilities are still not well elucidated. Hereby,
we analyzed differential light availabilities on the relationship between stomatal characters and leaf growth, as well as
photosynthetic performance. We used either 450–500 μmol m−2 s−1 as high light (HL) or 80–100 μmol m−2 s−1 as low light (LL) as treatments for two different cultivars. Our results showed that the stomatal density (SD) and stomatal
index (SI) increased along with the leaf area expansion until the peak of the correlation curve, and then decreased. SD and
SI were lower under the LL condition after three days of leaf expansion. For both cultivars, downregulation of photosynthesis
and electron transport components was observed in LL-grown plants as indicated by lower light- and CO2-saturated photosynthetic rate (P
max and RuBPmax), quantum efficiency of photosystem II (PSII) photochemistry (ΦPSII), electron transport rate (ETR) and photochemical quenching of fluorescence (qp). The observed inhibition of the photosynthesis could be explained by the decrease of SD, SI, Rubisco content and by the
changes of the chloroplast. The low light resulted in lower total biomass, root/shoot ratio, and the thickness of the leaf
decreased. However, the specific leaf area (SLA) and the content of leaf pigments were higher in LL-treatment. Variations
in the photosynthetic characteristics of capsicum grown under different light conditions reflected the physiological adaptations
to the changing light environments. 相似文献
20.
CO2 assimilation, transpiration and modulated chlorophyll fluorescence of leaves of Chenopodium bonus-henricus (L.) were measured in the laboratory and, at a high altitude location, in the field. Direct calibration of chlorophyll fluorescence parameters against carbon assimilation in the presence of 1 or 0.5% oxygen (plus CO2) proved necessary to calculate electron transport under photorespiratory conditions in individual experiments. Even when stomata were open in the field, total electron transport was two to three times higher in sunlight than indicated by net carbon gain. It decreased when stomata were blocked by submerging leaves under water or by forcing them to close in air by cutting the petiole. Even under these conditions, electron transport behind closed stomata approached 10 nmol electrons m?2 leaf area s?1 at temperatures between 25 and 30 °C. No photoinactivation of photosystem II was indicated by fluorescence analysis after a day's exposure to full sunlight. Only when leaves were submerged in ice was appreciable photoinactivation noticeable after 4 h exposure to sunlight. Even then almost full recovery occurred overnight. Electron transport behind blocked stomata was much decreased when leaves were darkened for 70 min (in order to deactivate light-regulated enzymes of the Calvin cycle) before exposure to full sunlight. Brief exposure of leaves to HCN (to inhibit photoassimilation and photorespiration) also decreased electron transport drastically compared to electron transport in unpoisoned leaves with blocked stomata. Non-photochemical fluorescence quenching and reduction of QA, the primary electron acceptor of photosystem II was increased by HCN-poisoning. Very similar observations were made when glyceraldehyde was used instead of HCN to inhibit photosynthesis and photorespiration. In HCN-poisoned leaves, residual electron transport increased linearly with temperature and showed early light saturation revealing characteristics of the Mehler reaction. During short exposure of these leaves to photon flux densities equivalent to 25% of sunlight, no or only little photoinactivation of photosystem II was observed. However, prolonged exposure to sunlight caused inactivation even though non-photochemical quenching of chlorophyll fluorescence was extensive. Simultaneously, oxidation of cellular ascorbate and glutathione increased. Inactivation of photosystem II was reversible in dim light and in the dark only after short times of exposure to sunlight. Glyceraldehyde was very similar to HCN in increasing the sensitivity of photosystem II in leaves to sunlight. We conclude from the observations that the electron transport permitted by the interplay of photoassimilatory and photorespiratory electron transport is essential to prevent the photoinactivation of photosynthetic electron transport. The Mehler and Asada reactions, which give rise to strong nonphotochemical fluorescence quenching, are insufficient to protect the chloroplast electron transport chain against photoinactivation. 相似文献