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1.
The present study shows the importance of alternative oxidase (AOX) pathway in optimizing photosynthesis under high light (HL). The responses of photosynthesis and respiration were monitored as O 2 evolution and O 2 uptake in mesophyll protoplasts of pea pre‐incubated under different light intensities. Under HL (3000 µmol m ?2 s ?1), mesophyll protoplasts showed remarkable decrease in the rates of NaHCO 3‐dependent O 2 evolution (indicator of photosynthetic carbon assimilation), while decrease in the rates of respiratory O 2 uptake were marginal. While the capacity of AOX pathway increased significantly by two fold under HL, the capacity of cytochrome oxidase (COX) pathway decreased by >50% compared with capacities under darkness and normal light (NL). Further, the total cellular levels of pyruvate and malate, which are assimilatory products of active photosynthesis and stimulators of AOX activity, were increased remarkably parallel to the increase in AOX protein under HL. Upon restriction of AOX pathway using salicylhydroxamic acid (SHAM), the observed decrease in NaHCO 3‐dependent O 2 evolution or p‐benzoquinone (BQ)‐dependent O 2 evolution [indicator of photosystem II (PSII) activity] and the increase in total cellular levels of pyruvate and malate were further aggravated/promoted under HL. The significance of raised malate and pyruvate levels in activation of AOX protein/AOX pathway, which in turn play an important role in dissipating excess chloroplastic reducing equivalents and sustenance of photosynthetic carbon assimilation to balance the effects of HL stress on photosynthesis, was depicted as a model. 相似文献
2.
In a glasshouse, Bemisia tabaci infestation largely reduced response of photosynthesis to irradiance and CO 2 concentration of Mikania micrantha compared with the non-infested control (C) ones. The maximum irradiance-saturated photosynthetic rate ( P
max) and saturation irradiance (SI) of the infested M. micrantha were only 21.3 % and 6.5 % of the C-plants, respectively. B. tabaci infestation led to the reduction of contents of chlorophyll and carotenoids in M. micrantha, which was accompanied with the decrease of actual photosystem 2 (PS2) efficiency (Φ PS2), efficiency of excitation energy capture by open PS2 reaction centres (F v′/F m′), electron transport rate (ETR), and photochemical quenching (q P). Moreover, superoxide dismutase and catalase activities significantly decreased while proline and glutathione contents significantly
increased in infested M. micrantha. Hence B. tabaci infestation not only induced direct damage of photosynthetic apparatus but also altered the antioxidant enzymes activities
in M. micrantha, which might as consequences accelerate senescence of this weed. 相似文献
3.
Cross stress of heat and high irradiance (HI) resulted in the accumulation of active oxygen species and photo-oxidative damage
to photosynthetic apparatus of wheat leaves during grain development. Pre-treatment with calcium ion protected the photosynthetic
system from oxidative damage by reducing O -.
2 production, inhibiting lipid peroxidation, and retarding electrolyte leakage from cell. Therefore, high F v/F m [maximal photochemical efficiency of photosystem 2 (PS2) while all PS2 reaction centres are open], F m/F 0 (another expression for the maximal photochemical efficiency of PS2), Φ PS2 (actual quantum yield of PS2 under actinic irradiation), q P (photochemical quenching coefficient), and P
N (net photosynthetic rate) were maintained, and lower q NP (non-photochemical quenching coefficient) of the leaves was kept under heat and HI stress. EGTA (a chelant of calcium ion)
and LaCl 3 (a blocker of Ca 2+ channel in cytoplasmic membrane) had the opposite effect. Thus Ca ion may help protect the photosynthetic system of wheat
leaves from oxidative damage induced by the cross stress of heat and HI. 相似文献
4.
Infiltration of methyl viologen (MV, source of O 2
–) and Na-diethyldithiocarbamate (DDC, inhibitor of SOD) into wheat leaves resulted in the accumulation of active oxygen species and photo-oxidative damage to photosynthetic apparatus under both moderate and high irradiance. Exogenous antioxidants, ascorbate (ASA) and mannitol, scavenged active oxygen efficiently, protected the photosynthetic system from MV and DDC induced oxidative damage, and maintained high F v/F m [maximal photochemical efficiency of photosystem 2 (PS2) while all PS2 reaction centres are open], F m/F 0 (another expression for the maximal photochemical efficiency of PS2), PS2 (actual quantum yield of PS2 under actinic irradiation), q P (photochemical quenching coefficient), P
N (net photosynthetic rate), and lowered q NP (non-photochemical quenching coefficient) of the leaves kept under high irradiance and oxidative stress. Phenolic compounds used in these experiments, catechol (Cat), resorcinol (Res), and tannic acid (Tan), had similar anti-oxidative activity and protective effect on photosynthetic apparatus as ASA and mannitol. The anti-oxidative activity and the protective effect of phenolic compounds increased with increase in their concentration from 100 to 300 g m –3. The number and the position of hydroxyl group in phenolic molecules seemed to influence their antioxidative activity. 相似文献
5.
Growth, photosynthetic gas exchange, and chlorophyll fluorescence characteristics were investigated in wild type (WT) and
Cd-sensitive mutant rice ( Oryza sativa L.) plants using 50 μM Cd treatment for 12 d followed by a 3-d recovery. Under Cd stress, net dry mass and pigment contents
were significantly lower in the mutant plants than in the WT. The mutant had lower net photosynthetic rate ( P
N), transpiration rate ( E), and stomatal conductance ( g
s) than WT rice, however, it had higher intercellular CO 2 concentration ( C
i), indicating that non-stomatal factors accounted for the inhibition of P
N. Maximal photochemical efficiency of photosystem 2 (F v/F m), effective quantum yield of PS2 (Φ PS2), and photochemical quenching (q P) decreased much in the mutant under Cd stress. Cd content in roots and leaves of the mutant was significantly higher than
those in the WT. Hence Cd toxicity was associated with the marked increases in Cd contents of plant tissue. After the recovery
for 3 d, the WT rice had higher capacity to recover from Cd injury than the mutant. 相似文献
6.
Trehalose can reduce stomatal aperture by a hydrogen-peroxide-dependent pathway in Vicia faba L. (cv. Daqingpi) resulting in significantly lower values of net photosynthetic rate (P N), stomatal conductance (g s), and transpiration rate (E). At 8 and 24 h, the lower P N in trehalose-treated plants was accompanied by significant decrease in intercellular CO 2 concentration (c i) suggesting that the reduction of P N was caused by stomatal limitation. At 48 and 72 h, trehalose decreased apparent carboxylation efficiency (P N/c i) and did not decrease c i and g s compared with controls; therefore the reduction in photosynthesis was caused by non-stomatal limitation. Trehalose treatment resulted in significantly higher effective photochemical efficiency of PS II (Φ PSII) and did not affect maximum photochemical efficiency of PS II (F v/F m). At 24, 48, and 72 h, trehalose decreased non-photochemical quenching (NPQ) and increased photochemical quenching (qP). Our results suggest that trehalose did not damage photosynthetic reaction centers. 相似文献
7.
Comparative analysis revealed that a xantha rice mutant (cv. Huangyu B) had higher ratios of chlorophyll (Chl) a/b and carotenoids/Chl, and higher photosynthetic efficiency than its wild type parent (cv. II32 B). Unexpectedly, the mutant
had higher net photosynthetic rate ( P
N) than II32 B. This might have resulted from its lower non-photochemical quenching (q N) but higher maximal photochemical efficiency (F V/F M), higher excitation energy capture efficiency of photosystem 2 (PS2) reaction centres (F V′/F M′), higher photochemical quenching (q P), higher effective PS2 quantum yield (Φ PS2), and higher non-cyclic electron transport rate (ETR). This is the first report of a chlorophyll mutant that has higher photosynthetic
efficiency and main Chl fluorescence parameters than its wild type. This mutant could become a unique material both for the
basic research on photosynthesis and for the development of high yielding rice cultivars. 相似文献
9.
以杂交酸模(Rumex K-1)为试材,研究了不同光强下线粒体交替氧化酶呼吸途径(AOX途径)对酸模叶片光破坏的防御作用.结果表明:在200 μmol·m-2·s-1弱光下,用水杨基羟肟酸抑制AOX途径后,Rumex K-1叶片的PSⅡ实际光化学效率、光合线性电子传递速率以及光合放氧速率均显著下降,非还原性QB反应中心显著升高,加重了叶片的光抑制,而活性氧清除机制上调,避免了活性氧的过量积累,部分缓解了Rumex K-1叶片的光抑制;在800 μmol·m-2·s-1强光下,AOX途径受抑,导致Rumex K-1叶片发生严重的光抑制,而此时活性氧清除机制的上调不足以缓解活性氧过量的积累.无论在强光还是弱光下,AOX途径在Rumex K-1叶片的光破坏防御过程中都起着重要作用,而且在强光下,AOX途径对叶片的光破坏防御作用是叶绿体内其他光破坏防御途径所不能代替的. 相似文献
10.
Plant growth, chlorophyll (Chl) content, photosynthetic gas exchange, ribulose-1,5-bisphosphate carboxylase (RuBPCO) enzyme
activity, and Chl fluorescence in radish ( Raphanus sativus var. longipinnatus) plants were examined after turnip mosaic virus (TuMV) infection. Plant fresh mass, dry mass, Chl content, net photosynthetic
rate ( P
N), transpiration rate ( E), stomatal conductance ( g
s), and RuBPCO activity were significantly lower in infected plants after 5 weeks of virus infection as compared to healthy
plants. The 5-week virus infection did not induce significant differences in intercellular CO 2 concentration ( C
i, photochemical efficiency of photosystem 2, PS2 (F v/F m), excitation capture efficiency of open PS2 reaction centres (F v'/F m'), effective quantum efficiency of photosystem 2 (ΔF/F m'), and photochemical quenching (q P), but non-photochemical quenching (q N) and alternative electron sink (AES) were significantly enhanced. Thus the decreased plant biomass of TuMV-infected plants
might be associated with the decreased photosynthetic activity mainly due to reduced RuBPCO activity. 相似文献
11.
Two rice chlorophyll (Chl) b-less mutants (VG28-1, VG30-5) and the respective wild type (WT) plant (cv. Zhonghua No. 11) were analyzed for the changes
in Chl fluorescence parameters, xanthophyll cycle pool, and its de-epoxidation state under exposure to strong irradiance,
SI (1 700 μmol m −2 s −1). We also examined alterations in the chloroplast ultrastructure of the mutants induced by methyl viologen (MV) photooxidation.
During HI (0–3.5 h), the photoinactivation of photosystem 2 (PS2) appeared earlier and more severely in Chl b-less mutants than in the WT. The decreases in maximal photochemical efficiency of PS2 in the dark (F v/F m), quantum efficiency of PS2 electron transport (Φ PS2), photochemical quenching (q P), as well as rate of photochemistry (P rate), and the increases in de-epoxidation state (DES) and rate of thermal dissipation of excitation energy (D rate) were significantly greater in Chl b-mutants compared with the WT plant. A relatively larger xanthophyll pool and 78–83 % conversion of violaxanthin into antheraxanthin
and zeaxanthin in the mutants after 3.5 h of HI was accompanied with a high ratio of inactive/total PS2 (0.55–0.73) and high
1–q P (0.57–0.68) which showed that the activities of the xanthophyll cycle were probably insufficient to protect the photosynthetic
apparatus against photoinhibition. No apparent difference of chloroplast ultrastructure was found between Chl b-less mutants and WT plants grown under low, LI (180 μmol m −2 s −1) and high, HI (700 μmol m −2 s −1) irradiance. However, swollen chloroplasts and slight dilation of thylakoids occurred in both mutants and the WT grown under
LI followed by MV treatment. These typical symptoms of photooxidative damage were aggravated as plants were exposed to HI.
Distorted and loose scattered thylakoids were observed in particular in the Chl b-less mutants. A greater extent of photoinhibition and photooxidation in these mutants indicated that the susceptibility to
HI and oxidative stresses was enhanced in the photosynthetic apparatus without Chl b most likely as a consequence of a smaller antenna size. 相似文献
12.
We examined photosynthetic activities and thermostability of photosystem 2 (PS2) in leaves of elm ( Ulmus pumila) seedlings from initiation to full expansion. During leaf development, net photosynthetic rate ( P
N) increased gradually and reached the maximum when leaves were fully developed. In parallel with the increase of P
N, chlorophyll (Chl) content was significantly elevated. Chl a fluorescence measurements showed that the maximum quantum yield of PS2 (ϕ PS2), the efficiency a trapped exciton, moved an electron into the electron transport chain further than Q A
− (Ψ o), and the quantum yield of electron transport beyond Q A (ϕ Eo) increased gradually. These results were independently confirmed by our low irradiance experiments. When subjected to progressive
heat stress, the young leaves exhibited considerably lower ϕ PS2 and higher minimal fluorescence (F 0) than the mature leaves, revealing the highly sensitive nature of PS2 under heat in the newly initiating leaves. Further
analysis showed that PS2 structure in the newly initiating leaves was strongly altered under heat, as evidenced by the increased
fluorescence signals at the position of the K step. We therefore demonstrated an inhibition in the oxygen-evolving complex
(OEC) in the young leaves. This resulted in decrease in amount of the functional PS2 reaction centres and relative increase
in the PS2 reaction centres with inhibited electron transport at the acceptor side under heat. We suggest that the enhanced
thermostability of PS2 during leaf development is associated with improved OEC stability. 相似文献
13.
A single treatment with a low pH solution of bean plants led to serious changes in the net photosynthetic rate ( P
N) as well as in various parameters of photosystem 2 (PS2) activity. A considerable suppression of P
N was established already in the first hours (3 and 5) following the acid treatment (pH 2.4-1.8). The period of strong inhibition
of CO 2 uptake and photochemical activity was followed by the period of recovery (24-72 h). At a single spraying, pH values exceeding
2.0 did not lead to irreversible damages of the photosynthetic apparatus. The damages resulting from treatments with pH 2.0
and 1.8 were on the threshold of irreversible ones and were the cause of faster ageing.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
The relation between oxygen evolution rate (OER) and quantum yield of photochemical reactions in photosystem 2 (Φ PS2) was examined in lichen symbiotic alga Trebouxia erici Ahmadjian (strain UTEX 911) exposed to different irradiances and osmotic stress (2 M sucrose for 60 h). Linear relationship
was found between OER and Φ PS2 in control cell suspension within irradiance range of 0 – 500 μmol m −2 s −1. Under osmotic stress, OER and Φ PS2 were significantly reduced. Relation between OER and Φ PS2 was curvilinear due to strong osmotically-induced inhibition of OER at high irradiance. The highest used irradiance (500
μmol m −2 s −1) was photoinhibitory for osmotically-stressed T. erici because non-photochemical quenching (NPQ) increased substantially. Energy-dependent quenching represented major part of NPQ
increase. Osmotic stress led also to the reduction of capacity of photochemical processes in PS 2 (F V/F M) and increase in F 0/F M. These changes indicated negative effects of osmoticum on structure and function of photosynthetic apparatus. 相似文献
15.
The photosynthetic performance and related leaf traits of Incarvillea delavayi Bur. et Franch were studied at different water regimes to assess its capacity for photosynthetic acclimation to water stress. The
initial response of I. delavayi to water stress was the closure of stomata, which resulted in down-regulation of photosynthesis. The stomatal limitation
(S L) represented the main component to photosynthetic limitations but non-stomatal limitation (NS L) increased quickly with the increasing water stress, and had similar magnitude to SL under severe water stress (soil moisture
25–30 % of field capacity). Chlorophyll (Chl) a fluorescence parameters characterizing photosystem (PS) 2 photochemical efficiency (Φ PS2), electron transport rate (J) and photochemical quenching (qP) decreased with the increasing water stress, indicating impaired
photosynthetic apparatus. However, the water-stressed plants had a increased mesophyll CO 2 diffusional conductance, Chl a/ b ratio, leaf nitrogen partitioning in RuBPCO and bioenergetics in later grown parts, indicating that I. delavay had a substantial physiological plasticity and showed a good tolerance to water stress. 相似文献
16.
Plant growth, contents of photosynthetic pigments, photosynthetic gas exchange, and chlorophyll (Chl) fluorescence in soybean
[ Glycine max (L.) Merr. cv. Heinong37] were investigated after it was inoculated with Sinorhizobium fredii USDA191 or treated with 5 mM (NH 4) 2SO 4 (N5) and 30 mM (NH 4) 2SO 4 (N30), respectively. In the plants following N5 fertilization, not only plant biomass, leaf area, and Chl content, but also
net photosynthetic rate ( P
N), stomatal conductance ( g
s), carboxylation efficiency (CE), maximum photochemical efficiency (F v/F m) of photosystem 2 (PS2), and quantum yield of PS2 (Φ PS2) were markedly improved as compared with the control plants. There were also positive effects on plant growth and plant photosynthesis
after rhizobia inoculation, but the effects were much less than those of N5 fertilization. For N30 plants there were no significant
positive effects on plant growth and photosynthetic capacity. Plant biomass, P
N, and g
s were similar to those of N-limited (control) plants. Φ PS2 and photochemical quenching (q P) were obviously declined while content of carotenoids and non-photochemical quenching (q N) were significantly enhanced in N30 treated plants. This indicated that excess N supply may cause some negative effects on
soybean plants. 相似文献
17.
以“农普”12号菜豆幼苗为材料,采用1mmol·L -1的水杨基氧肟酸(SHAM)抑制交替呼吸途径活性,探讨了在CuCl 2胁迫下交替呼吸途径对菜豆幼苗叶片光系统Ⅱ的保护作用。结果表明,随着CuCl 2胁迫浓度的增加,菜豆幼苗叶片潜在最大光化学效率F v/F m、光适应下叶片的最大光化学效率F v'/F m'、PSⅡ的实际光化学效率Y(Ⅱ)以及光化学猝灭系数qP、叶绿素含量均呈下降趋势,而非光学猝灭系数NPQ和交替呼吸途径的容量水平则呈上升趋势。较之在CuCl 2处理下的菜豆幼苗,用交替呼吸途径抑制剂预处理后的菜豆再置于CuCl 2的胁迫下,则会导致F v/F m、F v'/F m'、Y(Ⅱ)、qP以及叶绿素含量的进一步下降和NPQ的进一步上升。上述观察表明,在CuCl 2胁迫下交替呼吸途径可以缓解PSⅡ光化学效率的下降、维持PSⅡ反应中心的开放程度、减少天线色素的热耗散以及缓解叶绿素含量的降低,从而保护菜豆叶片光系统Ⅱ免受CuCl 2胁迫的伤害。 相似文献
18.
Methyl viologen (MV) is a well-known electron mediator that works on the acceptor side of photosystem I. We investigated the
little-known, MV-induced inhibition of linear electron flow through photosystem II (PS II) in spinach-leaf discs. Even a low
[MV] decreased the (1) average, light-adapted photochemical efficiency of PS II traps, (2) oxidation state of the primary
quinone acceptor Q A in PS II during illumination, (3) photochemical efficiency of light-adapted open PS II traps, (4) fraction of absorbed light
energy dissipated constitutively in a light-independent manner or as chlorophyll (Chl) a fluorescence emission, (5) Chl a fluorescence yield corresponding to dark-adapted open reaction-center traps ( F
o) and closed reaction-center traps ( F
m), and (6) half-time for re-oxidation of Q A− in PS II after a single-turnover flash. These effects suggest that the presence of MV accelerates various “downhill” electron-transfer
steps in PS II. Therefore, when using the MV to quantify cyclic electron flow, the inhibitory effect of MV on PS II should
be taken into account. 相似文献
19.
Photosynthetic rate (P N) and chlorophyll (Chl) fluorescence induction of source leaves in response to a low sink demand created by girdling the branch
(GB) between the root-tuber-system and the leaves were studied in Dahlia pinnata L. cv. Rigolet during the stage of rapid tuber growth in the greenhouse. GB resulted in significantly lower values of P N, stomatal conductance (g s), and transpiration rate (E), but in higher leaf temperature (T l) compared with those of controls. With exception of maximum quantum yield of photosystem 2 (PS 2) photochemistry (F v/F m) and maximum ratio of quantum yields of photochemical and concurrent non-photochemical processes in PS 2 (F v/F 0), no significant differences were observed in Chl fluorescence parameters between girdled and control leaves on days 1 and
2 after GB, indicating no apparent damage in the photosynthetic apparatus. However, longer girdling duration resulted in higher
non-photochemical Chl fluorescence quenching (NPQ), but lower F v/F 0, actual efficiency of energy conversion in PS 2 under steady-state conditions (Φ PS2), and photochemical quenching coefficient (qP) in comparison with controls from 10:00 to 16:00 or 15:00 on days 4 and 5,
respectively, indicating reversible injury in the photosynthetic apparatus. 相似文献
20.
Main conclusion
This study describes a new role for hydroperoxide lyase branch of oxylipin biosynthesis pathway in protecting photosynthetic apparatus under high light conditions.
Lipid-derived signaling molecules, oxylipins, produced by a multi-branch pathway are central in regulation of a wide range of functions. The two most known branches, allene oxide synthase (AOS) and 13-hydroperoxide lyase (HPL) pathways, are best recognized as producers of defense compounds against biotic challenges. In the present work, we examine the role of these two oxylipin branches in plant tolerance to the abiotic stress, namely excessive light. Towards this goal, we have analyzed variable chlorophyll fluorescence parameters of intact leaves of Arabidopsis thaliana genotypes with altered oxylipin profile, followed by examining the impact of exogenous application of selected oxylipins on functional activity of photosynthetic apparatus in intact leaves and isolated thylakoid membranes. Our findings unequivocally bridge the function of oxylipins to photosynthetic processes. Specifically, HPL overexpressing lines display enhanced adaptability in response to high light treatment as evidenced by lower rate constant of photosystem 2 (PS2) photoinhibition and higher rate constant of PS2 recovery after photoinhibition. In addition, exogenous application of linolenic acid, 13-hydroperoxy linolenic acid, 12-oxophytodienoic acid, and methyl jasmonate individually, suppresses photochemical activity of PS2 in intact plants and isolated thylakoid membranes, while application of HPL-branch metabolites—does not. Collectively these data implicate function of HPL branch of oxylipin biosynthesis pathway in guarding PS2 under high light conditions, potentially exerted through tight regulation of free linolenic acid and 13-hydroperoxy linolenic acid levels, as well as competition with production of metabolites by AOS-branch of the oxylipin pathway. 相似文献
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