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1.
The combined effects of ozone (O3) and drought on isoprene emission were studied for the first time. Young hybrid poplars (clone 546, Populus deltoides cv. 55/56 x P. deltoides cv. Imperial) were exposed to O3 (charcoal‐filtered air, CF, and non‐filtered air +40 ppb, E‐O3) and soil water stress (well‐watered, WW, and mild drought, MD, one‐third irrigation) for 96 days. Consistent with light‐saturated photosynthesis (Asat), intercellular CO2 concentration (Ci) and chlorophyll content, isoprene emission depended on drought, O3, leaf position and sampling time. Drought stimulated emission (+38.4%), and O3 decreased it (?40.4%). Ozone increased the carbon cost per unit of isoprene emission. Ozone and drought effects were stronger in middle leaves (13th–15th from the apex) than in upper leaves (6th–8th). Only Asat showed a significant interaction between O3 and drought. When the responses were up‐scaled to the entire‐plant level, however, drought effects on total leaf area translated into around twice higher emission from WW plants in clean air than in E‐O3. Our results suggest that direct effects on plant emission rates and changes in total leaf area may affect isoprene emission from intensively cultivated hybrid poplar under combined MD and O3 exposure, with important feedbacks for air quality.  相似文献   

2.
Plants can avoid freezing damage by preventing extracellular ice formation below the equilibrium freezing temperature (supercooling). We used Olea europaea cultivars to assess which traits contribute to avoid ice nucleation at sub‐zero temperatures. Seasonal leaf water relations, non‐structural carbohydrates, nitrogen and tissue damage and ice nucleation temperatures in different plant parts were determined in five cultivars growing in the Patagonian cold desert. Ice seeding in roots occurred at higher temperatures than in stems and leaves. Leaves of cold acclimated cultivars supercooled down to ?13 °C, substantially lower than the minimum air temperatures observed in the study site. During winter, leaf ice nucleation and leaf freezing damage (LT50) occurred at similar temperatures, typical of plant tissues that supercool. Higher leaf density and cell wall rigidity were observed during winter, consistent with a substantial acclimation to sub‐zero temperatures. Larger supercooling capacity and lower LT50 were observed in cold‐acclimated cultivars with higher osmotically active solute content, higher tissue elastic adjustments and lower apoplastic water. Irreversible leaf damage was only observed in laboratory experiments at very low temperatures, but not in the field. A comparative analysis of closely related plants avoids phylogenetic independence bias in a comparative study of adaptations to survive low temperatures.  相似文献   

3.
Xylella fastidiosa is a xylem‐limited bacterial plant pathogen that causes bacterial leaf scorch in its hosts. Our previous work showed that water stress enhances leaf scorch symptom severity and progression along the stem of a liana, Parthenocissus quinquefolia, infected by X. fastidiosa. This paper explores the photosynthetic gas exchange responses of P. quinquefolia, with the aim to elucidate mechanisms behind disease expression and its interaction with water stress. We used a 2 × 2‐complete factorial design, repeated over two growing seasons, with high and low soil moisture levels and infected and non‐infected plants. In both years, low soil moisture levels reduced leaf water potentials, net photosynthesis and stomatal conductance at all leaf positions, while X. fastidiosa‐infection reduced these parameters at basally located leaves only. Intercellular CO2 concentrations were reduced in apical leaves, but increased at the most basal leaf location, implicating a non‐stomatal reduction of photosynthesis in leaves showing the greatest disease development. This result was supported by measured reductions in photosynthetic rates of basal leaves at high CO2 concentrations, where stomatal limitation was eliminated. Repeated measurements over the summer of 2000 showed that the effects of water stress and infection were progressive over time, reaching their greatest extent in September. By reducing stomatal conductances at moderate levels of water stress, P. quinquefolia maintained relatively high leaf water potentials and delayed the onset of photosynthetic damage due to pathogen and drought‐induced water stress. In addition, chlorophyll fluorescence measurements showed that P. quinquefolia has an efficient means of dissipating excess light energy that protects the photosynthetic machinery of leaves from irreversible photoinhibitory damage that may occur during stress‐induced stomatal limitation of photosynthesis. However, severe stress induced by disease and drought eventually led to non‐stomatal decreases in photosynthesis associated with leaf senescence.  相似文献   

4.
External characteristics of the leaf epidermis and their effects on behaviour of Aphis gossypii Glover were evaluated in two Cucumis melo L. genotypes, ‘Bola de Oro’ (aphid susceptible) and TGR‐1551 (aphid resistant) in order to explore their role in the early rejection of TGR‐1551 by this aphid. No differential effects of epicuticular waxes on aphid behaviour were observed. The type, distribution and number of trichomes on melon leaves were also studied. Pubescence in melon, measured as the number of non‐glandular trichomes per cm2, was not sufficient to prevent aphid settling. However, there was a high density of type I glandular trichomes on leaves of the aphid‐resistant genotype. According to microscopic observations and stain testing, these trichomes store and secrete phenols and flavonoids. Free‐choice tests were conducted to determine the effect of these glandular trichomes on A. gossypii preference, revealing that aphids reject leaf disks of TGR‐1551 from the onset of the experiment. Additional experiments after removal of leaf type I glandular trichome exudates showed that A. gossypii preferred washed TGR‐1551 leaf disks over unwashed disks, while this effect was not observed in experiments using washed and unwashed ‘Bola de Oro’ leaf disks. These results suggest that a high density of glandular trichomes and chemicals secreted by them deter A. gossypii and disturb aphid settling on TGR‐1551.  相似文献   

5.
1. Littorella uniflora and Lobelia dortmanna are prominent small rosette species in nutrient‐poor, soft‐water lakes because of efficient root exchange of CO2 and O2. We hypothesise that higher gas exchange across the leaves of L. uniflora than of L. dortmanna ensures O2 uptake from water and underlies its greater tolerance to sediment anoxia following organic enrichment. 2. We studied plant response to varying sediment O2 demand and biogeochemistry by measuring photosynthesis, gas exchange across leaves and O2 dynamics in plants during long‐term laboratory and field studies. Frequent non‐destructive sampling of sediment pore water was used to track changes in sediment biogeochemistry. 3. Addition of organic matter triggered O2 depletion and accumulation of , Fe2+ and CO2 in sediments. Gas exchange across leaf surfaces was 13–16 times higher for L. uniflora than for L. dortmanna. Oxygen in the leaf lacunae of L. uniflora remained above 10 kPa late at night on anoxic sediments despite organic enrichment. Leaf content of N and P of L. uniflora remained sufficient to keep up photosynthesis despite prolonged sediment anoxia, whereas nutrient content was too low for long‐term survival of L. dortmanna. 4. High gas exchange across L. uniflora leaves improves its performance and survival on anoxic sediments compared with L. dortmanna. Lobelia dortmanna uses the same gas‐tight leaves in air and water, which makes it highly susceptible to sediment anoxia but more cost‐effective in ultra‐oligotrophic environments because of slow leaf turnover.  相似文献   

6.
7.
The photosynthetic performance (leaf gas exchange and chlorophyll a (Chla) fluorescence), activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX)] and the concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in the flag leaves of plants from two wheat cultivars with contrasting levels of resistance to spot blotch was assessed. Spot blotch severity was significantly lower in plants from cv. BR‐18 compared to cv. Guamirim. Net carbon assimilation rate, stomatal conductance and concentrations of Chla, Chlab and carotenoids were significantly decreased from fungal infection. In contrast, internal CO2 concentration was significantly increased from fungal infection in comparison to their non‐inoculated counterparts. Similarly, inoculation significantly reduced photochemical performance in the inoculated flag leaves in comparison to their non‐inoculated counterparts. However, plants from cv. BR‐18 were able to sustain greater functionality of the photosynthetic apparatus during fungal infection process compared to cv. Guamirim. The activities of SOD, POX, APX and CAT increased in inoculated flag leaves from both cultivars compared to non‐inoculated plants, and the highest increases were measured in cv. BR‐18. The greater activities of these enzymes were associated with a reduced H2O2 concentration in the inoculated flag leaves from cv. BR‐18, resulting, therefore, in a lower MDA concentration. Thus, a more efficient antioxidative system in flag leaves from cv. BR‐18 plays a pivotal role in removing the excess reactive oxygen species that were generated during the infection process of Bipolaris sorokiniana, therefore limiting cellular damage and largely preserving the photosynthetic efficiency of the infected flag leaves.  相似文献   

8.
The penetration behaviour of the pathogen Venturia nashicola, which causes scab disease in Asian pears, was studied at the ultrastructural and cytochemical levels in host and non‐host leaves. We show, for the first time, that before V. nashicola penetrated the cuticle of the epidermis of the pear leaf, the appressorial bottom of the pathogen invaginated to form a cavity that contains electron‐dense material. The leaf cuticle beneath the cavity also became highly electron dense following penetration by V. nashicola. The location of these electron‐dense materials at the sites of penetration of the pathogen into plant cell walls suggests that they might be related to enzymes capable of degrading cell walls and that the cavities might be needed for successful penetration of leaves by V. nashicola. The generation of hydrogen peroxide (H2O2) was observed in penetration‐related infection structures of V. nashicola, such as appressorial bottoms, infection sacs, penetration pegs and necks of subcuticular hyphae regardless of whether the interaction of V. nashicola with pear plants was compatible or incompatible. Nonetheless, more H2O2 was generated at the sites of the structures in scab‐inoculated susceptible leaves than that in scab‐inoculated resistant ones. Furthermore, the decrease in the level of H2O2 generation following treatment with the antioxidant ascorbic acid partially prevented the penetration of the cuticle. Therefore, the generation of H2O2 from the penetration‐related structures might be a pathogenicity factor that contributes to strengthening the penetration peg of V. nashicola.  相似文献   

9.
By altering myriad aspects of leaf chemistry, increasing concentrations of CO2 and O3 in the atmosphere derived from human activities may fundamentally alter the relationships between insect herbivores and plants. Because exposure to elevated CO2 can alter the nutritional value of leaves, some herbivores may increase consumption rates to compensate. The effects of O3 on leaf nutritional quality are less clear; however, increased senescence may also reduce leaf quality for insect herbivores. Additionally, changes in secondary chemistry and the microclimate of leaves may render plants more susceptible to herbivory in elevated CO2 and O3. Damage to soybean (Glycine max L.) leaves and the size and composition of the insect community in the plant canopy were examined in large intact plots exposed to elevated CO2 (~550 μmol mol−1) and elevated O3 (1.2*ambient) in a fully factorial design with a Soybean Free Air Concentration Enrichment system (SoyFACE). Leaf area removed by folivorous insects was estimated by digital photography and insect surveys were conducted during two consecutive growing seasons, 2003 and 2004. Elevated CO2 alone and in combination with O3 increased the number of insects and the amount of leaf area removed by insect herbivores across feeding guilds. Exposure to elevated CO2 significantly increased the number of western corn rootworm (Diabrotica virgifera) adults (foliage chewer) and soybean aphids (Aphis glycines; phloem feeder). No consistent effect of elevated O3 on herbivory or insect population size was detected. Increased loss of leaf area to herbivores was associated with increased carbon-to-nitrogen ratio and leaf surface temperature. Soybean aphids are invasive pests in North America and new to this ecosystem. Higher concentrations of CO2 in the atmosphere may increase herbivory in the soybean agroecosystem, particularly by recently introduced insect herbivores. Handling editor: Gary Felton.  相似文献   

10.
Atmospheric change may affect plant phenolic compounds, which play an important part in plant survival. Therefore, we studied the impacts of CO2 and O3 on the accumulation of 27 phenolic compounds in the short‐shoot leaves of two European silver birch (Betula pendula Roth) clones (clones 4 and 80). Seven‐year‐old soil‐grown trees were exposed in open‐top chambers over three growing seasons to ambient and twice ambient CO2 and O3 concentrations singly and in combination in central Finland. Elevated CO2 increased the concentration of the phenolic acids (+25%), myricetin glycosides (+18%), catechin derivatives (+13%) and soluble condensed tannins (+19%) by increasing their accumulation in the leaves of the silver birch trees, but decreased the flavone aglycons (?7%) by growth dilution. Elevated O3 increased the concentration of 3,4′‐dihydroxypropiophenone 3‐β‐d ‐glucoside (+22%), chlorogenic acid (+19%) and flavone aglycons (+4%) by inducing their accumulation possibly as a response to increased oxidative stress in the leaf cells. Nevertheless, this induction of antioxidant phenolic compounds did not seem to protect the birch leaves from detrimental O3 effects on leaf weight and area, but may have even exacerbated them. On the other hand, elevated CO2 did seem to protect the leaves from elevated O3 because all the O3‐derived effects on the leaf phenolics and traits were prevented by elevated CO2. The effects of the chamber and elevated CO2 on some compounds changed over time in response to the changes in the leaf traits, which implies that the trees were acclimatizing to the altered environmental conditions. Although the two clones used possessed different composition and concentrations of phenolic compounds, which could be related to their different latitudinal origin and physiological characteristics, they responded similarly to the treatments. However, in some cases the variation in phenolic concentrations caused by genotype or chamber environment was much larger than the changes caused by either elevated CO2 or O3.  相似文献   

11.
Vegetative anatomical features are poorly known in the South American genus Chrysolaena. In this study, leaves and stems of six Chrysolaena species were described and compared morphologically and anatomically using diaphanization, microtome serial sectioning and scanning electron microscopy. The species differed in leaf epidermis, type of stomata, shape of anticlinal walls of epidermal cells, trichome density, and presence or absence in stems of small air spaces in the cortical parenchyma and of druse‐shaped oxalate crystals. Furthermore, glandular trichomes and three types of non‐glandular trichomes with different number of basal cells were identified on leaves and stems. Collectively, these features proved instrumental to discriminate among the six studied species, suggesting that leaves and stems of Chrysolaena can represent a source for taxonomically useful characters. We also discuss anatomical features in relation to the environmental conditions in the species’ habitats.  相似文献   

12.
Diurnal changes in photosynthetic gas exchange and chlorophyll fluorescence were measured under full sunlight to reveal diffusional and non‐diffusional limitations to diurnal assimilation in leaves of Arisaema heterophyllum Blume plants grown either in a riparian forest understorey (shade leaves) or in an adjacent deforested open site (sun leaves). Midday depressions of assimilation rate (A) and leaf conductance of water vapour were remarkably deeper in shade leaves than in sun leaves. To evaluate the diffusional (i.e. stomatal and leaf internal) limitation to assimilation, we used an index [1–A/A350], in which A350 is A at a chloroplast CO2 concentration of 350 μ mol mol ? 1. A350 was estimated from the electron transport rate (JT), determined fluorometrically, and the specificity factor of Rubisco (S), determined by gas exchange techniques. In sun leaves under saturating light, the index obtained after the ‘peak’ of diurnal assimilation was 70% greater than that obtained before the ‘peak’, but in shade leaves, it was only 20% greater. The photochemical efficiency of photosystem II ( Δ F/Fm ′ ) and thus JT was considerably lower in shade leaves than in sun leaves, especially after the ‘peak’. In shade leaves but not in sun leaves, A at a photosynthetically active photon flux density (PPFD) > 500 μ mol m ? 2 s ? 1 depended positively on JT throughout the day. Electron flows used by the carboxylation and oxygenation (JO) of RuBP were estimated from A and JT. In sun leaves, the JO/JT ratio was significantly higher after the ‘peak’, but little difference was found in shade leaves. Photorespiratory CO2 efflux in the absence of atmospheric CO2 was about three times higher in sun leaves than in shade leaves. We attribute the midday depression of assimilation in sun leaves to the increased rate of photorespiration caused by stomatal closure, and that in shade leaves to severe photoinhibition. Thus, for sun leaves, increased capacities for photorespiration and non‐photochemical quenching are essential to avoid photoinhibitory damage and to tolerate high leaf temperatures and water stress under excess light. The increased Rubisco content in sun leaves, which has been recognized as raising photosynthetic assimilation capacity, also contributes to increase in the capacity for photorespiration.  相似文献   

13.
The non‐invasive leaf patch clamp pressure (LPCP) probe measures the attenuated pressure of a leaf patch, Pp, in response to an externally applied magnetic force. Pp is inversely coupled with leaf turgor pressure, Pc, i.e. at high Pc values the Pp values are small and at low Pc values the Pp values are high. This relationship between Pc and Pp could also be verified for 2‐m tall olive trees under laboratory conditions using the cell turgor pressure probe. When the laboratory plants were subjected to severe water stress (Pc dropped below ca. 50 kPa), Pp curves show reverse diurnal changes, i.e. during the light regime (high transpiration) a minimum Pp value, and during darkness a peak Pp value is recorded. This reversal of the Pp curves was completely reversible. Upon watering, the original diurnal Pp changes were re‐established within 2–3 days. Olive trees in the field showed a similar turnover of the shape of the Pp curves upon drought, despite pronounced fluctuations in microclimate. The reversal of the Pp curves is most likely due to accumulation of air in the leaves. This assumption was supported with cross‐sections through leaves subjected to prolonged drought. In contrast to well‐watered leaves, microscopic inspection of leaves exhibiting inverse diurnal Pp curves revealed large air‐filled areas in parenchyma tissue. Significantly larger amounts of air could also be extracted from water‐stressed leaves than from well‐watered leaves using the cell turgor pressure probe. Furthermore, theoretical analysis of the experimental Pp curves shows that the propagation of pressure through the nearly turgorless leaf must be exclusively dictated by air. Equations are derived that provide valuable information about the water status of olive leaves close to zero Pc.  相似文献   

14.
Abstract Young, amphistomatous hybrid poplar (Populus deltoides x trichocarpa) plants were exposed daily to either background (0.025 cm3 m-3) or elevated (0.125 cm3 m-3) concentrations of O3. Levels of abaxial and adaxial leaf conductance were affected interactively by pollutant treatment, leaf age, and photon fluence rate. Consequently, conductance in O3-treated leaves was sometimes higher and sometimes lower than in comparable control leaves, depending on leaf age or level of photon fluence rate. For example, at low photon fluence rate or in the dark, conductance was greater in O3-treated than in control plants, while at high photon fluence rate that relationship was reversed. Exposure to O3 also reduced the water-use efficiency and range of leaf conductance of individual leaves, and altered the relationship between the conductances of the two leaf surfaces (the ratio of abaxial to adaxial leaf conductance was increased). Furthermore, O3 treatment resulted in diminished stomatal control of water loss; excised O3-treated leaves had higher conductances and wilted sooner than excised control leaves of identical ages. Overall, the data indicate that exposure to O3 resulted in impaired stomatal function.  相似文献   

15.
Ziziphora L. is represented by 5 species and 2 subspecies in the flora of Turkey: Z. clinopodioides, Z. capitata, Z. persica, Z. tenuior, Z. taurica subsp. taurica, Z. taurica subsp. cleonioides. It is difficult to distinguish between some Ziziphora taxa because of their morphological similarities. In this study, the leaf and calyx trichomes of Ziziphora taxa in Turkey were studied in order to assess anatomical variations that may serve as distinguishing characters. Their micromorphological features were surveyed by scanning electron microscopy (SEM) and light microscopy (LM). Trichomes on leaves and calyx can be divided into two general types: non‐glandular trichomes and glandular (secretory) trichomes. The non‐ glandular trichomes are simple, acicular or curved with cuticular micropapillae. They usually consist of one or more additional cells. The glandular trichomes are divided into two types: peltate and capitate and Ziziphora taxa can easily be distinguished by presence/absence, density and types of glandular trichomes on leaves and calyx. The peltate trichomes consist of 12 or 18 secretory head cells in a single disc; four or six central cells surrounded by eight or twelve peripheral ones. Peltate trichomes are absent on the adaxial leaf surface of Z. capitata and Z. persica. Two types of capitate trichomes are present in Ziziphora. The capitate trichomes are only absent on the calyx surface of Z. persica. In addition, the trichome micromorphology provides some support for separating the two subspecies of Z. taurica. In conclusion, Ziziphora taxa can easily be distinguished by cell number, cell shape presence/absence and density of the glandular trichomes on leaves and calyx.  相似文献   

16.
Experiments were conducted to determine the fate of nitrogen (N) remobilized as a result of ozone (O3)‐induced accelerated senescence in hybrid poplar subjected to declining N availability concurrent with O3 stress. Cuttings were grown in sand culture where the supply of N to the plant could be controlled on a daily basis and reduced in half of the plants when desired. Plants all initially received 3·57 mm N daily until approximately the 20 leaf stage after which daily supply of N was reduced to 0·71 mm . Plants were grown in open‐top chambers in the field (Rock Springs, PA, USA) and received charcoal‐filtered air, half also received supplemental O3 to a level of 0·08 µL L?1. Allocation of newly acquired N was determined with 15N. The specific allocation (mg labelled N mg?1 total N) of labelled N to upper, expanding leaf N was not affected by O3, but was strongly affected by N treatment. However, O3 increased the relative partitioning of labelled N to the expanding leaves and the roots. The balance between partitioning of newly acquired N to the upper leaves and roots was not affected by O3, but was reduced by N withdrawal. Calculated net N flux was strongly negative in the lower leaves of O3‐exposed, N withdrawal plants. Nitrogen uptake was not reduced by O3. The allometric relationships between the roots and shoots were not affected by O3 or N availability. The relative contribution of newly acquired versus remobilized N to new growth appears to be determined by N supply. Ozone exposure alters the allocation of newly acquired N via alterations in plant size, whereas N availability exerts a strong effect upon both plant size and N allocation.  相似文献   

17.
Considerable soybean yield losses caused by ozone (O3) stress have been demonstrated by large‐scale meta‐analyses of free‐gas concentration enrichment systems. In this study, comparative proteomic approach was employed to explore the differential changes of proteins in O3 target structures such as leaf and chloroplasts of soybean seedlings. Acute O3 exposure (120 parts‐per‐billion) for 3 days did not cause any visible symptoms in developing leaves. However, higher amounts of ROS and lipid peroxidation indicated that severe oxidative burst occurred. Immunoblot analysis of O3‐induced known proteins revealed that proteins were modulated before symptoms became visible. Proteomic analysis identified a total of 20 and 32 differentially expressed proteins from O3‐treated leaf and chloroplast, respectively. Proteins associated with photosynthesis, including photosystem I/II and carbon assimilation decreased following exposure to O3. In contrast, proteins involved in antioxidant defense and carbon metabolism increased. The activity of enzymes involved in carbohydrate metabolism increased following exposure to O3, which is consistent with the decrease in starch and increase in sucrose concentrations. Taken together, these results suggest that carbon allocation is tightly programmed, and starch degradation probably feeds the tricarboxylic acid cycle while the photosynthesis pathway is severely affected during O3 stress.  相似文献   

18.
Hydrogen peroxide is an important signalling molecule, involved in regulation of numerous metabolic processes in plants. The most important sources of H2O2 in photosynthetically active cells are chloroplasts and peroxisomes. Here we employed variegated Pelargonium zonale to characterise and compare enzymatic and non‐enzymatic components of the antioxidative system in autotrophic and heterotrophic leaf tissues at (sub)cellular level under optimal growth conditions. The results revealed that both leaf tissues had specific strategies to regulate H2O2 levels. In photosynthetic cells, the redox regulatory system was based on ascorbate, and on the activities of thylakoid‐bound ascorbate peroxidase (tAPX) and catalase. In this leaf tissue, ascorbate was predominantly localised in the nucleus, peroxisomes, plastids and mitochondria. On the other hand, non‐photosynthetic cells contained higher glutathione content, mostly located in mitochondria. The enzymatic antioxidative system in non‐photosynthetic cells relied on the ascorbate–glutathione cycle and both Mn and Cu/Zn superoxide dismutase. Interestingly, higher content of ascorbate and glutathione, and higher activities of APX in the cytosol of non‐photosynthetic leaf cells compared to the photosynthetic ones, suggest the importance of this compartment in H2O2 regulation. Together, these results imply different regulation of processes linked with H2O2 signalling at subcellular level. Thus, we propose green‐white variegated leaves as an excellent system for examination of redox signal transduction and redox communication between two cell types, autotrophic and heterotrophic, within the same organ.  相似文献   

19.
Ascorbate in leaf apoplast (ASCapo) reacts with ozone (O3) and thereby reduces O3 flux reaching plasmalemma (Fpl). Some studies have shown significant protection of cells from O3 by ASCapo, while others have questioned its efficacy. Hypothesizing that the protection by ASCapo depends on other variables, we quantified determinants of O3 detoxification with a model of O3 transport and reaction in apoplast. The model determines ascorbic acid concentration in apoplast (AAapo) using measured values of O3 concentration (co), leaf tissue ascorbic acid concentration (AAleaf), cell wall thickness (L3), apoplastic pH (pHapo), and stomatal conductance (Gsw). We compared the measured and model‐estimated AAapo in leaves of peach (Prunus persica) grown in open‐top chambers under non‐filtered air (NF) and elevated (EO3: NF + 80 ppb) O3 concentrations. The estimated AAapo in individual leaves agreed well with the measured values (R2 = .91). Analyses of the simulation results yielded the following findings: (a) The efficacy of O3 reduction with ASCapo as quantified by fractional reduction (?3) of O3 flux at the surface of plasmalemma (Fpl) was lowered from 70% in NF to 40% in EO3 due to the reduction of L3. The EO3 reduced AAapo, but the lower Gsw and L3 in EO3 increased AAapo resulting in no significant change in AAapo due to EO3. ?3 can be calculated with measured values of AAapo and L3, and Fpl can be estimated with the measurement‐based ?3. (b) When c0 is increased, Fpl increased curvilinearly with the increase of Fst: nominal O3 flux via stomatal diffusion, exhibiting apparent threshold on Fst. The deviation of Fpl from Fst became greater when L3, pHapo, and AAleaf were increased. The quantification of ?3 and Fpl using leaf traits shall facilitate the understanding of the mechanisms of differential plant sensitivity to O3 and improve quantification of the O3 impacts on plants.  相似文献   

20.
The individual and combined effects of elevated CO2 and O3 on the foliar chemistry of silver birch (Betula pendula Roth) and on the performance of five potential birch‐defoliating insect herbivore species (two geometrid moths, one lymantrid moth and two weevils) were examined. Elevated CO2 decreased the water concentration in both short‐ and long‐shoot leaves, but the effect of CO2 on the concentration of nitrogen and individual phenolic compounds was mediated by O3 treatment, tree genotype and leaf type. Elevated O3 increased the total carbon concentration only in short‐shoot leaves. Bioassays showed that elevated CO2 increased the food consumption rate of juvenile Epirrita autumnata and Rheumaptera hastata larvae fed with short‐ and long‐shoot leaves in spring and mid‐summer, respectively, but had no effect on the growth of larvae. The contribution of leaf quality variables to the observed CO2 effects indicate that insect compensatory consumption may be related to leaf age. Elevated CO2 increased the food preference of only two tested species: Phyllobius argentatus (CO2 alone) and R. hastata (CO2 combined with O3). The observed stimulus was dependent on tree genotype and the measured leaf quality variables explained only a portion of the stimulus. Elevated O3 decreased the growth of flush‐feeding young E. autumnata larvae, irrespective of CO2 concentration, apparently via reductions in general food quality. Therefore, the increasing tropospheric O3 concentration could pose a health risk for juvenile early‐season birch folivores in future. In conclusion, the effects of elevated O3 were found to be detrimental to the performance of early‐season insect herbivores in birch whereas elevated CO2 had only minor effects on insect performance despite changes in food quality related foliar chemistry.  相似文献   

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