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1.
Ole Pedersen Sarah Meghan Rich Timothy David Colmer 《The Plant journal : for cell and molecular biology》2009,58(1):147-156
When completely submerged, the leaves of some species retain a surface gas film. Leaf gas films on submerged plants have recently been termed 'plant plastrons', analogous with the plastrons of aquatic insects. In aquatic insects, surface gas layers (i.e. plastrons) enlarge the gas–water interface to promote O2 uptake when under water; however, the function of leaf gas films has rarely been considered. The present study demonstrates that gas films on leaves of completely submerged rice facilitate entry of O2 from floodwaters when in darkness and CO2 entry when in light. O2 microprofiles showed that the improved gas exchange was not caused by differences in diffusive boundary layers adjacent to submerged leaves with or without gas films; instead, reduced resistance to gas exchange was probably due to the enlarged water–gas interface (cf. aquatic insects). When gas films were removed artificially, underwater net photosynthesis declined to only 20% of the rate with gas films present, such that, after 7 days of complete submergence, tissue sugar levels declined, and both shoot and root growth were reduced. Internal aeration of roots in anoxic medium, when shoots were in aerobic floodwater in darkness or when in light, was improved considerably when leaf gas films were present. Thus, leaf gas films contribute to the submergence tolerance of rice, in addition to those traits already recognized, such as the shoot-elongation response, aerenchyma and metabolic adjustments to O2 deficiency and oxidative stress. 相似文献
2.
ALAN R. WELLBURN 《The New phytologist》1998,139(1):5-9
Air quality thresholds for O3 for the protection of human health and vegetation set by the European Union (EU) have been exceeded in Europe regularly in the 1990s. Because target reductions for oxides of nitrogen (NOx ) set for the year 2000 are unlikely to be achieved, these O3 exceedances are likely to continue into the next millenium. Improvements of plant tolerance towards O3 are being investigated but very little work has been done to explore NOx tolerance and plant acclimation to NO2 and NO. However, it is clear that within the populations of some plant species there is wide variation, and some individuals can fix NOx and use the nitrogen directly from the atmosphere, rather than rely upon, for example, root uptake of nitrate. It is possible that individuals capable of fixing NOx could be selected for a range of species, and genotypes with high rates of uptake could be of value as crops or for forestation in polluted areas (e.g. landscaping in the vicinity of motorways) to reduce tropospheric concentrations of NOx significantly and also to decrease the potential for O3 production. 相似文献
3.
Sensing soil oxygen 总被引:6,自引:0,他引:6
M. C. DREW 《Plant, cell & environment》1990,13(7):681-693
Abstract. Under natural conditions where gaseous exchange between soil and atmosphere is restricted by excess water, the concentration of O2 in the rooting zone can become very low while reduced ions and organic compounds that are potentially phytoxic may accumulate. Mechanisms by which shoots and roots detect, and adjust to, this O2 -deficient environment are reviewed. Injury to roots and their inability to function because of insufficient O2 is communicated to the shoot in a variety of ways, so that it adjusts physiologically. Roots may acclimate metabolically to a gradual fall in O2 supply, so that they either improve their tolerance of anoxia, or partially avoid O2 -deficiency by structural changes that aid internal transfer of O2 to the roots from the shoot. Molecular mechanisms regulating such metabolic changes, including environmental cues, are discussed. 相似文献
4.
Routine oxygen consumption rates of juvenile spot, Leiostomus xanthums , were measured over a range of temperatures, salinities and fish weights. As predicted, Q O2 increased with temperature and decreased with body weight. However, Q O2 decreased with decreasing salinity and did not show the expected minimum at isosmotic concentrations. The data are best described by the relationship: log10 Q O2 (mg O2 g−1 h−1 ) = 0.129 loglo salinity (%0) + 1.604 log10 temperature (°C)-0.1401og10 (g)-2.767. 相似文献
5.
Differential response of four tree species to ozone-induced acceleration of foliar senescence 总被引:7,自引:1,他引:6
E. J. Pell J. P. Sinn B. W. Brendley L. Samuelson C. Vinten-Johansen M. Tien & J. Skillman 《Plant, cell & environment》1999,22(7):779-790
Ozone (O3 )-induced accelerated senescence of leaves was measured in four tree species: black cherry ( Prunus serotina ), hybrid poplar ( Populus maximowizii x trichocarpa , clone 245), northern red oak ( Quercus rubra ) and sugar maple ( Acer saccharum ). Seedlings or ramets of the four species were subjected to chronic O3 exposures and designated leaves harvested periodically from emergence to senescence. Gas exchange was analysed, and concentrations of total soluble protein and ribulose-1,5-bisphosphate carboxylase/oxygenase were measured as indicators of leaf senescence. Total antioxidant potential and ascorbate peroxidase and glutathione reductase activities also were determined. Black cherry and hybrid poplar exhibited O3 -induced accelerated leaf senescence, whereas sugar maple and northern red oak did not. When the O3 effects were related to cumulative uptake of the gas, black cherry was the most sensitive of the four species. Although hybrid poplar exhibited similar symptoms of O3 -induced accelerated senescence after the same exposure period as did black cherry, this species took up much greater quantities of O3 to achieve the same response. The O3 -induced increase in glutathione reductase activity in hybrid poplar was consistent with the capacity of this species to take up high concentrations of the gas. Relative tolerance of northern red oak and sugar maple could be explained only in part by lower cumulative O3 uptake and lower rate of uptake. Sugar maple had the highest antioxidant potential of all four species, which may have contributed to O3 tolerance of this species. Ascorbate peroxidase activity, when expressed on a fresh weight basis, could not account for differential sensitivity among the four species. 相似文献
6.
Abstract. The rate of O2 consumption was measured in five coprophilous beetle species (common in Denmark) at O2 concentrations from 1–21%. With the exception of the mainly soil-living Geotrupes spiniger (Marsham) (Geotrupidae), these beetles are probably exposed to severe hypoxia in fresh cattle pats. Aphodius fossor (Linnaeus), A. contaminatus (Herbst) (Aphodiidae) and Sphaeridium lunatum Fabricius (Hydrophilidae) maintained normal movements and a normal rate of 02 uptake (for at least 30 min) at only 1% O2 . There is no evidence, therefore, that the beetles switch to anaerobic metabolism under these conditions. This ability to regulate respiration, and hence to extract 02 at very low concentrations, is exceptional even among terrestrial arthropods living in soil or other potentially hypoxic substrates. In A. rufipes (Linnaeus), respiration declined at ambient concentrations below 2% O2 , and in G. spiniger the ability to regulate respiration seemed to fail at even higher concentrations. In four of the species (G. spiniger was not tested), about 11% CO2 (the level in a dung pat at 2% O2 ) did not affect the O2 uptake at 2% O2 . 相似文献
7.
Effects of elevated oxygen tensions on acetylene reduction in Alnus incana-Frankia symbioses 总被引:1,自引:0,他引:1
An open flow-through gas system was used to determine the effect of C2 H2 and elevated O2 on acetylene reduction activity (ARA) and respiration of the intact, potted root system of Alnus incana (L.) Moench in symbiosis with Frankia Avcll or with a local source of Frankia . Both symbiotic systems responded to C2 H2 by an immediate plateau range in ARA. The Plateau in ARA was in some cases followed by a decline of less extent than reported for many legumes. A concurrent decline in net respiration of the root system was on average 8% of the CO2 efflux prior to C2 H2 introduction.
Respiration of the root systems in both symbioses responded to elevated oxygen levels in the 10 kPa C2 H2 atmosphere by an increase of up to 17% of the net respiration prior to C2 H2 introduction in 21 kPa O2 . In contrast, the elevated oxygen levels resulted in an immediate drop in ARA followed by a minor increase to a stable level lower than that at the preceding, lower oxygen tension. The symbiosis with the local Frankia had lost all ARA when the partial pressure of O2 exceeded 50 kPa, whereas the symbiosis with Avcll still had some activity at 80 kPa O2 . This difference in tolerance of elevated O2 clearly shows that the oxygen exclusion mechanisms may be controlled by the microsymbiont in Alnus-Frankia symbioses. The symbiotic systems recovered ARA to a similar extent when returned from elevated O2 levels to 21 kPa O2 . 相似文献
Respiration of the root systems in both symbioses responded to elevated oxygen levels in the 10 kPa C
8.
We repeatedly sampled the surface mineral soil (0–20 cm depth) in three northern temperate forest communities over an 11-year experimental fumigation to understand the effects of elevated carbon dioxide (CO2 ) and/or elevated phyto-toxic ozone (O3 ) on soil carbon (C). After 11 years, there was no significant main effect of CO2 or O3 on soil C. However, within the community containing only aspen ( Populus tremuloides Michx.), elevated CO2 caused a significant decrease in soil C content. Together with the observations of increased litter inputs, this result strongly suggests accelerated decomposition under elevated CO2. In addition, an initial reduction in the formation of new (fumigation-derived) soil C by O3 under elevated CO2 proved to be only a temporary effect, mirroring trends in fine root biomass. Our results contradict predictions of increased soil C under elevated CO2 and decreased soil C under elevated O3 and should be considered in models simulating the effects of Earth's altered atmosphere. 相似文献
9.
Soil oxygen flux was measured polarographically in undisturbed tussock tundra and in an old vehicle track at Eagle Creek, Alaska. Because some polarograms did not show effective voltage plateaus, the polarographic method was tested for use in the tundra by experimental manipulation of soil water content and microbial oxygen demand. The response of soil oxygen flux was as predicted for artificially waterlogged systems, and the response to increased microbial demand indicated relatively high oxygen availability. Soil oxygen flux ranged from 25.9 ng O2 cm−2 min−1 in Sphagnum mats to 3.9 ng O2 cm−2 min−1 in unvegetated ruts of the vehicle track. Most sites in unvegetated ruts did not have measurable soil oxygen flux. In contrast, oxygen flux beneath Eriophorum vaginatum tussocks growing in the vehicle track averaged 10.7 ng O2 cm−2 min−1 . 相似文献
10.
Respiration measured as CO2 efflux was determined at various soil O2 and CO2 concentrations for individual, attached roots of a succulent perennial from the Sonoran Desert, Agave deserti Engelm. The respiration rate increased with increasing O2 concentration up to about 16% O2 for established roots and 5% O2 for rain roots (fine branch roots on established roots induced by wetting of the soil) and then remained fairly constant up to 21% O2 . When O2 was decreased from 21 to 0%, the respiration rates were similar to those obtained with increasing O2 concentration. The CO2 concentration in the root zone, which for the shallow-rooted A. deserti in the field was about 1 000 μl l-1 , did not affect root respiration at concentrations up to 2 000 μl l-1 , but higher concentrations reduced it, respiration being abolished at 20 000 μl l-1 (2%) CO2 for both established and rain roots. Upon lowering CO2 to 1 000 μl l-1 after exposure to concentrations up to 10000 μl l-1 CO2 , inhibition of respiration was reversible. Uptake of the vital stain neutral red by root cortical cells was reduced to zero, indicating cell death, in about 4 h at 2% CO2 , substantiating the detrimental effects of high soil CO2 concentrations on roots of A. deserti . This CO2 response may explain why roots of desert succulents tend to occur in porous, well-aerated soils. 相似文献
11.
I. Scheurwater C. Cornelissen F. Dictus R. Welschen & H. Lambers 《Plant, cell & environment》1998,21(10):995-1005
Herbaceous plants grown with free access to nutrients exhibit inherent differences in maximum relative growth rate (RGR) and rate of nutrient uptake. Measured rates of root respiration are higher in fast-growing species than in slow-growing ones. Fast-growing herbaceous species, however, exhibit lower rates of respiration than would be expected from their high rates of growth and nitrate uptake. We investigated why the difference in root O2 uptake between fast- and slow-growing species is relatively small. Inhibition of respiration by the build-up of CO2 in closed cuvettes, diurnal variation in respiration rates or an increasing ratio of respiratory CO2 release to O2 uptake (RQ) with increasing RGR failed to explain the relatively low root respiration rates in fast-growing grasses. Furthermore, differences in alternative pathway activity can at most only partly explain why the difference in root respiration between fast- and slow-growing grasses is relatively small. Although specific respiratory costs for maintenance of biomass are slightly higher in the fast-growing Dactylis glomerata L. than those in the slow-growing Festuca ovina L., they account for 50% of total root respiration in both species. The specific respiratory costs for ion uptake in the fast-growing grass are one-third of those in the slow-growing grass [0·41 versus 1·22 mol O2 mol (NO3 – )–1 ]. We conclude that this is the major cause of the relatively low rates of root respiration in fast-growing grasses. 相似文献
12.
We present, for the first time, the oxygen response kinetics of mitochondrial respiration measured in intact leaves (sunflower and aspen). Low O2 concentrations in N2 (9–1500 ppm) were preset in a flow-through gas exchange measurement system, and the decrease in O2 concentration and the increase in CO2 concentration as result of leaf respiration were measured by a zirconium cell O2 analyser and infrared-absorption CO2 analyser, respectively. The low O2 concentrations little influenced the rate of CO2 evolution during the 60-s exposure. The initial slope of the O2 uptake curve on the dissolved O2 concentration basis was relatively constant in leaves of a single species, 1.5 mm s−1 in sunflower and 1.8 mm s−1 in aspen. The apparent K 0.5 (O2 ) values ranged from 0.33 to 0.67 μ M in sunflower and from 0.33 to 1.1 μ M in aspen, mainly because of the variation of the maximum rate, V max (leaf temperature 22°C). The initial slope of the O2 response of respiration characterizes the catalytic efficiency of terminal oxidases, an important parameter of the respiratory machinery in leaves. The plateau of the response characterizes the activity of the mitochondrial electron transport chain and is subject to regulations in accordance with the necessity for ATP production. The relatively low oxygen conductivity of terminal oxidases means that in leaves, less than 10% of the photosynthetic oxygen can be reassimilated by mitochondria. 相似文献
13.
Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O2 larva−1 h−1 , of older yolk sac larvae 10.09 μl O2 larva−1 h−1 , and of one-month-old fry 32.99 μl O2 larva−1 h−1 . The QO2 values showed a decrease with development and growth, ranging from 21.2–26.0 μl O2 mg−1 h−1 in newly hatched larvae to 2.97 μl mg−1 h−1 in one-month-old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12-24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q10 factor increased from 2.25 to 3.43 with increasing size. Day-old yolk-sac larvae, late yolk-sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise. 相似文献
14.
Reetta Ahlfors Mikael Brosché Hannes Kollist Jaakko Kangasjärvi 《The Plant journal : for cell and molecular biology》2009,58(1):1-12
Nitric oxide (NO) is involved together with reactive oxygen species (ROS) in the activation of various stress responses in plants. We have used ozone (O3 ) as a tool to elicit ROS-activated stress responses, and to activate cell death in plant leaves. Here, we have investigated the roles and interactions of ROS and NO in the induction and regulation of O3 -induced cell death. Treatment with O3 induced a rapid accumulation of NO, which started from guard cells, spread to adjacent epidermal cells and eventually moved to mesophyll cells. During the later time points, NO production coincided with the formation of hypersensitive response (HR)-like lesions. The NO donor sodium nitroprusside (SNP) and O3 individually induced a large set of defence-related genes; however, in a combined treatment SNP attenuated the O3 induction of salicylic acid (SA) biosynthesis and other defence-related genes. Consistent with this, SNP treatment also decreased O3 -induced SA accumulation. The O3 -sensitive mutant rcd1 was found to be an NO overproducer; in contrast, Atnoa1/rif1 ( Arabidopsis nitric oxide associated 1/resistant to inhibition by FSM1 ), a mutant with decreased production of NO, was also O3 sensitive. This, together with experiments combining O3 and the NO donor SNP suggested that NO can modify signalling, hormone biosynthesis and gene expression in plants during O3 exposure, and that a functional NO production is needed for a proper O3 response. In summary, NO is an important signalling molecule in the response to O3 . 相似文献
15.
Amphipod gigantism dictated by oxygen availability? 总被引:3,自引:0,他引:3
A recent study of gigantism in amphipods proposes a novel mechanism which could be used to explain Bergmann's rule, namely differences in environmental O2 concentration. Consideration of the respiratory biology of this group indicates significant flaws in this proposal. Nonetheless, it is not unreasonable to predict a relationship between ectotherm body size and O2 partial pressure ( p O2 ) in some systems, where the partial pressure gradient is steep, either in time (comparison of Carboniferous and Permian atmospheres) or space (animals inhabiting oceanic O2 minimum layers, and, particularly in freshwaters, living at high altitude). Animal gigantism can be correlated with periods of very high environmental p O2 over geological time. Unfortunately, data for present day spatial patterns are scant. 相似文献
16.
In soybeans ( Glycine max L. Merr.), high levels of soil nitrate inhibit N2 fixation, and nitrate-tolerant symbioses have been identified within a chemically mutagenized line of cv. Bragg denoted nts382 and within the line K466, a genotype representative of a number of Korean soybean cultivars. The genotypes nts382 and K466 were examined to see if they could be used as a model system for studying the mechanism responsible for the short-term (i.e. 3-day) inhibition of specific nitrogenase activity, especially the mechanism behind the greater O2 limitation of nodule metabolism that is characteristic of nitrate inhibition of N2 fixation in soybean. In nts382, total nitrogenase activity (TNA = H2 production in Ar:O2 ) was inhibited to a lesser degree (48% of control) relative to Bragg (30% of control), and the nitrate-treated symbioses showed less of an O2 limitation of nodule metabolism in nts382 than in Bragg. However, the relative proportion of O2 limitation to the total nitrate inhibition was similar (40 and 41%) in nts382 and Bragg, respectively. Therefore, the nts382 symbioses may be useful in elucidating the general mechanism for down-regulation of nitrogenase activity in soybean, but would not be a useful model system for studying the control of O2 -limited metabolism following nitrate exposure. The effects of nitrate on TNA and on the degree of O2 limitation of nodule metabolism were the same in K466 and a reference cultivar Maple Arrow. Consequently, the tolerance of K466 to nitrate reported previously was attributed to the ability of this symbiosis to maintain nodule biomass in the presence of nitrate, not to any ability to maintain specific nitrogenase activity in the presence of nitrate. 相似文献
17.
In soybeans ( Glycine max L. Merr.), high levels of soil nitrate inhibit N2 fixation, and nitrate-tolerant symbioses have been identified within a chemically mutagenized line of cv. Bragg denoted nts382 and within the line K466, a genotype representative of a number of Korean soybean cultivars. The genotypes nts382 and K466 were examined to see if they could be used as a model system for studying the mechanism responsible for the short-term (i.e. 3-day) inhibition of specific nitrogenase activity, especially the mechanism behind the greater O2 limitation of nodule metabolism that is characteristic of nitrate inhibition of N2 fixation in soybean. In nts382, total nitrogenase activity (TNA = H2 production in Ar:O2 ) was inhibited to a lesser degree (48% of control) relative to Bragg (30% of control), and the nitrate-treated symbioses showed less of an O2 limitation of nodule metabolism in nts382 than in Bragg. However, the relative proportion of O2 limitation to the total nitrate inhibition was similar (40 and 41%) in nts382 and Bragg, respectively. Therefore, the nts382 symbioses may be useful in elucidating the general mechanism for down-regulation of nitrogenase activity in soybean, but would not be a useful model system for studying the control of O2 -limited metabolism following nitrate exposure. The effects of nitrate on TNA and on the degree of O2 limitation of nodule metabolism were the same in K466 and a reference cultivar Maple Arrow. Consequently, the tolerance of K466 to nitrate reported previously was attributed to the ability of this symbiosis to maintain nodule biomass in the presence of nitrate, not to any ability to maintain specific nitrogenase activity in the presence of nitrate. 相似文献
18.
A comparative study of the effects of NaCl salinity on respiration, photosynthesis, and leaf extension growth in Beta vulgaris L. (sugar beet) 总被引:1,自引:1,他引:0
Abstract. Three parameters influencing the capacity for carbon accumulation, i.e. photosynthesis, respiration, and leaf extension growth, were studied in Beta vulgaris L. (sugar beet) cultured in nutrient solution containing 0.5 to 500 mol m−3 NaCl. Leaf extension growth was the parameter most sensitive to salinity: the initial rate of leaf extension and final leaf length each declined linearly with increase in external NaCl concentration. Photosynthetic O2 evolution of thin leaf slices did not decline until salinity levels reached 350 to 500 mol m−3 NaCl, while respiratory O2 consumption was not affected by salinity throughout the range. The results suggest that the influence of salinity on the capacity for carbon accumulation in B. vulgaris occurs primarily through reduction in the area of photosynthetic surface. 相似文献
19.
In flood-tolerant species, a common response to inundation is growth of adventitious roots into the water column. The capacity for these roots to become photosynthetically active has received scant attention. The experiments presented here show the aquatic adventitious roots of the flood-tolerant, halophytic stem-succulent, Tecticornia pergranulata (subfamily Salicornioideae, Chenopodiaceae) are photosynthetic and quantify for the first time the photosynthetic capacity of aquatic roots for a terrestrial species. Fluorescence microscopy was used to determine the presence of chloroplasts within cells of aquatic roots. Net O2 production by excised aquatic roots, when underwater, was measured with varying light and CO2 regimes; the apparent maximum capacity ( P max ) for underwater net photosynthesis in aquatic roots was 0.45 µ mol O2 m−2 s−1 . The photosynthetic potential of these roots was supported by the immunolocalization of PsbA, the major protein of photosystem II, and ribulose-1-5-bisphosphate carboxylase/oxygenase (Rubisco) in root protein extracts. Chlorophyllous aquatic roots of T. pergranulata are photosynthetically active, and such activity is a previously unrecognized source of O2 , and potentially carbohydrates, in flooded and submerged plants. 相似文献
20.
Diazotrophic systems have developed a number of strategies to protect nitrogenase (N2 ase; EC 1.18.6.1) from O2 excess and active-oxygen species (AOS). Protection against O2 excess is given by biochemical modifications of N2 ase, increased rates of low-efficiency respiration, temporal segregation of N2 fixation and photosynthesis, physical barriers to O2 diffusion, and hemoglobins. On the other hand, AOS may originate from oxidation of N2 ase components, ferredoxins, flavodoxins and hemoglobins; interaction among the AOS themselves, or between H2 O2 and hemoglobins; and during reactions catalyzed by hydrogenase (EC 1.18.99.1), xanthine oxidase (EC 1.1.3.22) and uricase (EC 1.7.3.3). Active-oxygen species are scavenged enzymatically [superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6). peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11)] or through non-enzymic reaction with low-molecular-weight compounds (ascorbate, α-tocopherol, glutathione). 相似文献