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1.
The mechanism of SO2-induced changes in stomatal conductance(g) of alder was examined to determine if SO2 affects guardcell function directly or indirectly through the SO2-inducedchanges in photosynthesis. During experimental fumigations at SO2 concentrations of 33µmol m3 (0.08 µl l1), stomatal closurepreceded declines in net photosynthetic rate (A), indicatingthat SO2 can directly affect guard cells. From these and otherstudies it appears that the sequence of A and g responses maybe influenced by SO2 concentration as well as by species. Fumigation with SO2 did not cause increases in g, even whenthe intercellular substomatal CO2 concentration (ci) was reducedby 50 µmol mol1. Increases in g are not attributableto SO2 effects on the CO2-based stomatal control system. Key words: Air pollution, Alnus serrulata, gas exchange, stomata, sulphur dioxide 相似文献
2.
Changes in Growth and Quality Characteristics of Lucerne (Medicago sativa L.) in Response to Sulphur Dioxide Exposure under Field Conditions 总被引:2,自引:0,他引:2
The effects of SO2 on some growth and quality characteristicsof lucerne (Medicago sativa L.) were investigated by exposingplants to mean SO2 concentrations of 215, 78 or 2.8 µgm3 in open-top chambers for 166 d. Plants exposed to215 µg m3 had significantly lower shoot and rootweights compared with plants exposed to 78 µg m3,but not compared with control plants. Exposure to 215 or 78µg m 3 increased the plant shoot: root ratio, buthad no effect on leaf area. During the middle of the fumigationperiod, relative growth rate and net assimilation rate werehighest in plants exposed to 215 fig m, but these later fellbelow control values, and plants exposed to 78 µg m3had the highest relative growth rate and net assimilation rate.As the duration of exposure increased, an initial SO2-inducedstimulation of growth may have developed to toxicity at thehighest SO2 exposure. Exposure to SO2 depressed L-ascorbic acid concentrations inleaves, had no effect on foliar protein or starch concentrations,and increased the specific energy of shoots and plant sulphurconcentrations. The effect of SO2 on L-ascorbic acid concentrationsmay suggest a mechanism for reduced freezing tolerance of plantsafter exposure to SO2. Key words: SO2, Medicago sativa L., Growth 相似文献
3.
Hogan K.P.; Fleck I.; Bungard R.; Cheeseman J.M.; Whitehead D. 《Journal of experimental botany》1997,48(6):1289-1297
Red beech (Nothofagus fusca (Hook. F.) Oerst.; Fagaceae) andradiata pine (Pinus radiata D. Don; Pinaceae) were grown for16 months in large open-top chambers at ambient (37 Pa) andelevated (66 Pa) atmospheric partial pressure of CO2, and incontrol plots (no chamber). Summer-time measurements showedthat photosynthetic capacity was similar at elevated CO2 (lightand CO2-saturated value of 17.2 µmol m2 s1for beech, 13.5 µmol m2 s1 for pine), plantsgrown at ambient CO2 (beech 21.0 µmol2 s1,pine 14.9 µmol m2s1) or control plants grownwithout chambers (beech 23.2 µmol m2 s1,pine 12.9 µmol m2 s1). However, the higherCO2 partial pressure had a direct effect on photosynthetic rate,such that under their respective growth conditions, photosynthesisfor the elevated CO2 treatment (measured at 70 Pa CO2 partialpressure: beech 14.1 µmol m2 s1 pine 10.3)was greater than in ambient (measured at 35 Pa CO2: beech 9.7µmol m2 s1, pine 7.0 µmol m2s1) or control plants (beech 10.8 µmol m2s1, pine 7.2 µmol m2 s1). Measurementsof chlorophyll fluorescence revealed no evidence of photodamagein any treatment for either species. The quantity of the photoprotectivexanthophyll cycle pigments and their degree of de-epoxidationat midday did not differ among treatments for either species.The photochemical efficiency of photosystem II (yield) was lowerin control plants than in chamber-grown plants, and was higherin chamber plants at ambient than at elevated CO2. These resultssuggest that at lower (ambient) CO2 partial pressure, beechplants may have dissipated excess energy by a mechanism thatdoes not involve the xanthophyll cycle pigments. Key words: Carotenoids, chlorophyll fluorescence, photosynthesis, photoinhibition, photoprotection, xanthophyll cycle 相似文献
4.
The photosynthetic response to CO2 concentration, light intensityand temperature was investigated in water hyacinth plants (Eichhorniacrassipes (Mart.) Solms) grown in summer at ambient CO2 or at10000 µmol(CO2) mol1 and in winter at 6000 µmol(CO2)mol1 Plants grown and measured at ambient CO2 had highphotosynthetic rate (35 µmo1(CO2) m2 s1),high saturating photon flux density (15002000) µmolm2 s1 and low sensitivity to temperature in therange 2040 °C. Maximum photosynthetic rate (63 µmol(CO2)m2 s1) was reached at an internal CO2 concentrationof 800 µmol mol1. Plants grown at high CO2 in summerhad photosynthetic capacities at ambient CO2 which were 15%less than for plants grown at ambient CO2, but maximum photosyntheticrates were similar. Photosynthesis by plants grown at high CO2and high light intensity had typical response curves to internalCO2 concentration with saturation at high CO2, but for plantsgrown under high CO2 and low light and plants grown under lowCO2 and high light intensity photosynthetic rates decreasedsharply at internal CO2 concentrations above 1000 µmol1. Key words: Photosynthesis, CO2, enrichment, Eichhornia crassipes 相似文献
5.
Apparatus is described for exposing plants to low concentrationsof SO2 (50500µg m3 in air) and for measuringeffects on photosynthesis, dark respiration, and transpiration.Temperature, humidity, and irradiance in the chambers were controlledindependently, and fans ensured that leaf boundary layer resistanceswere low. Experiments with plants of Vicia faba in clean andpolluted air showed that: (i) a depression of net photosynthesisby 50 µg m3 SO2 depended on boundary layer resistanceand on irradiance; (ii) stomatal resistance was increased ordecreased by 50 µg m3 SO2 when relative humidityin the chambers was low (35% r.h., 22 °C) or high (50% r.h.,22 °C) respectively. 相似文献
6.
Barley (Hordeum vulgare L. cv. Digger) was grown for 22 d inenclosed chambers with a CO2 enrichment of 35, 155, 400 or 675µmol CO2 mol1. CO2 enrichment increased photosyntheticcapacity in the plants grown at either of the two highest levelsof pCO2. A CO2 enrichment of 675µmol CO2 caused a significantincrement of shoot dry weight, whereas no changes were observedin fresh weight, chlorophyll or protein levels. At a light intensityof 860µmol m2s1 CO2 enrichment caused photosyntheticcapacity to increase by 250%, whereas no effect was observedat 80 µmol m2 s1. Over time, photosynthesisdecreased by 70% independent of CO2. A time-dependent increasein the level of extractable fructose was observed whereas totalextractable carbohydrate only changed slightly. Key words: Carbohydrates, CO2 enrichment, Hordeum vulgare, photosynthesis, respiration 相似文献
7.
In this paper we report for the first time the occurrence ofan inducible weak CAM in leaves of Talinwn triangulare (Jacq.)Willd. This plant is a terrestrial perennial deciduous herbwith woody stems and succulent leaves which grows under fullexposure and in the shade in northern Venezuela. Plants grownin a greenhouse (sun plants) and a growth cabinet(shade plants) with daily irrigation showed CO2uptake only during the daytime (maximum rate, 4?0 µmolm2 s1) and a small acid accumulation during thenight (6?0 µmol H+g1 FW). Twenty-four hours aftercessation of irrigation, no CO2 exchange was observed duringpart of the night. Dark fixation reached a maximum (1?0 µmolCO2 m2 s1, 100 µmol H+ g1 FW) onday 9 of drought. By day 30 almost no gas exchange was observed,while acid accumulation was still 10 µmol H+ g1FW. Rewatering reverted the pattern of CO2 exchange to thatof a C3 plant within 24 h. Daytime and night-time phosphoenolpyruvatecarboxylase activity increased up to 100% (shade) and 62% (sun)of control values after 10 and 15 d of drought, respectively.Light compensation point and saturating irradiance were similarin well-watered sun and shade plants, values being characteristicof sun plants. CAM seems to be important for the tolerance ofplants of this species to moderately prolonged (up to 2 months)periods of drought in conditions of full exposure as well asshade, and also for regaining high photosynthetic rates shortlyafter irrigation. Key words: Talinum triwigulare, inducible CAM, PEP-C activity, recycling 相似文献
8.
Differentiating Day from Night Effects of High Ambient [CO2] on the Gas Exchange and Growth of Xanthium strumarium L. Exposed to Salinity Stress 总被引:2,自引:0,他引:2
Sodium chloride, at a concentration of 88 mol m-3in half strengthHoagland nutrient solution, increased dry weight per unit areaofXanthium strumarium L. leaves by 19%, and chlorophyll by 45%compared to plants grown without added NaCl at ambient (350µmol mol-1) CO2concentration. Photosynthesis, per unitleaf area, was almost unaffected. Even so, over a 4-week period,growth (dry weight increment) was reduced in the salt treatmentby 50%. This could be ascribed to a large reduction in leafarea (>60%) and to an approx. 20% increase in the rate ofdark respiration (Rd). Raising ambient [CO2] from zero to 2000 µmol mol-1decreasedRd in both control and salinized plants (by 20% at 1000, andby 50% at 2000 µmol mol-1CO2concentration) compared toRd in the absence of ambient CO2. High night-time [CO2] hadno significant effect on growth of non-salinized plants, irrespectiveof day-time ambient [CO2]. Growth reduction caused by salt wasreduced from 51% in plants grown in 350 µmol mol-1throughoutthe day, to 31% in those grown continuously in 900 µmolmol-1[CO2]. The effect of [CO2] at night on salinized plants depended onthe daytime CO2concentration. Under 350 µmol mol-1day-time[CO2], 900 µmol mol-1at night reduced growth over a 4-weekperiod by 9% (P <0.05) and 1700 µmol mol-1reduced itby 14% (P <0.01). However, under 900 µmol mol-1day-time[CO2], 900vs . 350 µmol mol-1[CO2] at night increasedgrowth by 17% (P <0.01). It is concluded that there is both a functional and an otiose(functionless) component to Rd, which is increased by salt.Under conditions of low photosynthesis (such as here, in thelow day-time [CO2] regime) the otiose component is small andhigh night-time [CO2] partly suppresses functional Rd, therebyreducing salt tolerance. In plants growing under conditionswhich stimulate photosynthesis (e.g. with increased daytime[CO2]), elevated [CO2] at night suppresses mainly the otiosecomponent of respiration, thus increasing growth. Consequently,in regions of adequate water and sunlight, the predicted furtherelevation of the world atmospheric [CO2] may increase plantsalinity tolerance. Xanthium strumarium ; respiration; photosynthesis; salt stress; sodium chloride; carbon dioxide; atmosphere 相似文献
9.
Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N2 fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO2, and temperature 23/18 °C day/night temperaturesat 680 µmol mol1 CO2, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol1 CO2 (C340)After 34 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO2 and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 1729%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO2 mol H2O1)was also significantly increased Plants acclimated to elevatedCO2, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves instantaneouslyexposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO2, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO2 at 23 °C increased graduallyfrom approx 10 % at 100 µmol m1 s1 to >27 % at 1170 µmol m2 s1 In parallel, wateruse efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 In parallel,water use efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 to approx100 % at the highest irradiance Elevated CO2, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO2 and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N2, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO2, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO2, elevated temperature, water use efficiency, N2 fixation 相似文献
10.
The Interaction Between Silicon and Aluminium in Sorghum bicolor (L.) Moench: Growth Analysis and X-ray Microanalysis 总被引:2,自引:0,他引:2
Seeds of Sorghum bicolor (L.) Moench. were germinated on moistfilter paper for 6 d, before the seedlings were transferredto pots containing 500 µmol l-1 Ca(NO3)2 for 2 d. Theseedlings were then treated with 0 or 100 µmol l-1 Alin factorial combination with 0, 1400 or 2800 µmol l-1Si for 8 d. The background solution used throughout was 500µmol l-1 Ca(NO3)2. Aluminium treatment reduced root growthand caused a significant increase in shoot/root ratio. The presenceof silica in the solution significantly ameliorated the effectsof aluminium on root growth. Three treatment were selected for a microanalytical investigationof the basal region of the root: 2800 µmol l-1 Si only;100 µmol l-1 Al only; and a combination of the two. Inthe 2800 µmol l-1 treatment silica was deposited in theendodermis, with the greatest accumulation being in the innertangential wall (ITW). When plants were treated with 100 µmoll-1 Al only, aluminium concentration was highest in the outertangential wall (OTW) of the epidermis. The element was presentin the hypodermal walls and OTW of the endodermis and was notdetectable in the stele. With both 2800 µmol l-1 Si and100 µmol l-1 Al in the nutrient solution the two biomineralizationsites were the ITW of the endodermis, where silicon was themajor element deposited, and atypically in the OTW of the epidermiswhere both aluminium and silicon were present. The sequestrationof aluminium in the Al-Si deposit in the OTW of the epidermismay represent the mechanism that allows greater root growthin this treatment.Copyright 1993, 1999 Academic Press Sorghum bicolor (L.) Moench., aluminium, silicon, calcium, root, toxicity, biomineralization, X-ray microanalysis, freeze substitution 相似文献
11.
Growth of Perennial Ryegrass (Lolium perenne L.) Exposed to a Low Concentration of Sulphur Dioxide 总被引:3,自引:0,他引:3
The influence of a low concentration of SO2 on the growth andsulphur status of perennial ryegrass (Lolium perenne L.) cv.S23 was examined in a system of specially designed growth chambers.For plants grown without additions of sulphate to the soil,erposure to ifitered air containing 50 µg m3 SO2alleviated sulphur deficiency that developed during a sequenceof successive harvests, and gave increased yield. The plantshad higher contents of organic and inorganic sulphur than thosegrown with neither sulphate nor SO2. Plants grown with addedsulphate showed no signs of sulphur deficiency and althoughexposure to SO2 increased their sulphur content it had no effecton yield. The coefficient of transpiration (g water transpiredg1 dry wt. of shoots) was reduced when plants which otherwisehad an inadequate supply of sulphur were exposed to SO2; forplants with adequate supplies of sulphate, it was similar whetherthey were grown with or without the addition of SO2 to the air.The results are discussed in relation to other known reactionsof plants to SO2. 相似文献
12.
Exposure of ryegrass (Lolium perenne L.) cv. S23 to 0, 50, and400 µg m3 SO2 for an initial 29 d (first harvest),and for an additional 22 d period of regrowth (second harvest),resulted in distinct alterations in carbohydrate metabolismat each harvest. At the first harvest, exposure to 50 µgm3 increased concentrations of free and total carbohydrates,whereas exposure to 400 µg m3 resulted in concentrationshardly different from those in control plants. At both SO2 concentrations,more assimilate was retained as free carbohydrate rather thanas storage carbohydrate. Comparison of assimilate distributionat the end of the light, and at the end of the dark period atthe first harvest led to the conclusion that light-mediatedmetabolism is more sensitive to SO2 exposure than dark metabolism,and that assimilate distribution might be controlled by at leasttwo processes exhibiting different SO2 sensitivities. 相似文献
13.
The Regulation of Citric Acid Accumulation and Carbon Recycling During CAM in Ananas comosus 总被引:4,自引:0,他引:4
The carbon balance of shade-grown Ananas comosus was investigatedwith regard to nitrogen supply and responses to high PAR. Netdark CO2 uptake was reduced from 61.2 to 38.5 mmol CO2 m2in N limited (N) plants grown under low PAR (60 µmolm2 s1) and apparent photon yield declined from0.066 to 0.034 (mol 02.mol1 photon), although photosyntheticcapacities (measured under 5% CO2) were similar. Following transferfor 7 d to high PAR (600. µmol m2 s1), netCO2 uptake at night increased by 14% in +N plants, and daytimephotosynthetic capacity was higher, with a maximum value of7.8 µmol m2 s1. The magnitude of dark CO2 fixation during CAM was measured asdawndusk variations in leaf-sap titratable acidity (H+)and as the proportion of malic and citric acids. The contributionfrom re-fixation of respiratory CO2 recycling (measured as thedifference between net CO2 uptake and malic acid accumulation)varied with growth conditions, although it was generally lower(30%) than reported for other bromeliads. Assuming a stoichiometryof 2H+: malate and 3H+: citrate, there was a good agreementbetween titratable protons and enzymatically determined organicacids. The accumulation of citric acid was related to nitrogensupply and PAR regime, increasing from 7.0 mol m3 (+Nplants) to 18 mol m3 (N plants) when plants weretransferred to high PAR; malate: citrate ratios decreased from13.1 to 2.5 under these conditions. Under the low PAR regime, leaf-sap osmotic pressure increasedat night in proportion to malic acid accumulation. However,following the transfer to high PAR for 7 d, there was a muchgreater depletion of soluble sugars at night which correspondedto a decrease in leaf-sap osmotic pressure. Although a rolefor citric acid in CAM has not been properly defined, it appearsthat the accepted stoichiometry for CAM in terms of gas exchange,titratable acidity, malic acid and osmotic pressure may nothold for plants which accumulate citric acid. Key words: Ananas comosus, CAM, citric acid accumulation, carbon recycling 相似文献
14.
The relationships between CO2 concentrating mechanisms, photosyntheticefficiency and inorganic carbon supply have been investigatedfor the aquatic macrophyte Littorella uniflora. Plants wereobtained from Esthwaite Water or a local reservoir, with thelatter plants transplanted into a range of sediment types toalter CO2 supply around the roots. Free CO2 in sediment-interstitial-waterranged from 101 mol m3 (Esthwaite), 0.79 mol m3(peat), 0.32 mol m3 (silt) and 017 mol m3(sand), with plants maintained under PAR of 40 µmol m2s1. A comparison of gross morphology of plants maintained underthese conditions showed that the peat-grown plants with highsediment CO2 had larger leaf fresh weight (069 g) andtotal surface area (223 cm2 g1 fr. wt. including lacunalsurface area) than the sand-grown plants (0.21 g and 196 cm2g1 fr. wt. respectively). Root fresh weights were similarfor all treatments. In contrast, leaf internal CO2 concentration[CO2], was highest in the sand-grown plants (269 molm3, corresponding to 6.5% CO2 in air) and lowest inthe Esthwaite plants (108 mol m3). Expressionof CAM in transplants was also greatest in the low CO2 regime,with H+ (measured as dawn-dusk titratable acidity) of 50µmolg fr. wt., similar to Esthwaite plants in natural sediment.Assuming typical CAM stoichiometry, decarboxylation of malatecould account largely for the measured [CO2]1 and would makea major contribution to daytime CO2 fixation in vivo. A range of leaf sections (02, 10, 50 and170 mm) was used to evaluate diffusion limitation andto select a suitable size for comparative studies of photosyntheticO2 evolution. The longer leaf sections (17.0 mm), which weresealed and included the leaf tip, were diffusion-limited witha linear response to incremental addition of CO2 and 10mol m3 exogenous CO2 was required to saturate photosynthesis.Shorter leaf sections were less diffusion-limited, with thegreatest photosynthetic capacity (36 µmol O2 g1 fr. wt. h1) obtainedfrom the 1.0 mm size and were not infiltrated by the incubatingmedium. Comparative studies with 1.0 mm sections from plants grown inthe different sediment types revealed that the photosyntheticcapacity of the sand-grown plants was greatest (45 µmolO2 g1 fr. wt. h1) with a K0.5 of 80 mmol m3.In terms of light response, saturation of photosynthesis intissue slices occurred at 8501000 µmol m2s1 although light compensation points (611 µmolm2s1) and chlorophyll a: b ratios (1.3) were low.While CO2 and PAR responses were obtained using varying numbersof sections with a constant fresh weight, the relationshipsbetween photosynthetic capacity and CO2 supply or PAR were maintainedwhen the data were expressed on a chlorophyll basis. It is concludedthat under low PAR, CO2 concentrating mechanisms interact inintact plants to maintain saturating CO2 levels within leaflacunae, although the responses of the various components ofCO2 supply to PAR require further investigation. Key words: Key words-Uttorella uniflora, internal CO2 concentration, crassulacean acid metabolism, root inorganic carbon supply, CO2 concentrating mechanism 相似文献
15.
16.
Defoliation in White Clover: Nodule Metabolism, Nodule Growth and Maintenance, and Nitrogenase Functioning During Growth and Regrowth 总被引:1,自引:0,他引:1
In two experiments, the functioning and metabolism of nodulesof white clover, following a defoliation which removed abouthalf the shoot tissue, were compared with those of undefoliatedplants. In one experiment, the specific respiration rates of nodulesfrom undefoliated plants varied between 1160 and 1830 µmolCO2 g1h1, of which nodule growth and maintenanceaccounted for 22 ± 2 per cent, or 27 ± 3.6 percent, according to method of calculation. Defoliation reducedspecific nodule respiration and nodule growth and maintenancerespiration by 6070 per cent, and rate of N2 fixationby a similar proportion. The original rate of nodule metabolismwas re-established after about 5 d of regrowth; during regrowthnodule respiration was quantitatively related to rate of N2,fixation: 9.1 µmol CO2 µmol1N2. With the possible exception of nodules examined 24 h after defoliation,the efficiency of energy utilization in nitrogenase functioningin both experiments was the same in defoliated and undefoliatedplants: 2.0±0.1 µmol CO2 µmol1 C2H4;similarly, there was no change in the efficiency of nitrogenasefunctioning as rate of N2 fixation increased with plant growthfrom 1 to 22 µmol N2 per plant h1. Exposure of nodulated white clover root systems to a 10 percent acetylene gas mixture resulted in a sharp peak in rateof ethylene production after 1.52.5 min; subsequently,rate of ethylene production declined rapidly before stabilisingafter 0.51 h at a rate about 50 per cent of that initiallyobserved. Regression of peak rate of ethyleneproduction on rate of N2 fixation indicated a value of 2.9 µmolC2H4 µmol1 N2, for rates of N2 fixation between1 and 22 µmol N2 per plant h1. The relationshipsbetween nitrogenase respiration, acetylene reduction rates andN2 fixation rates are discussed. Trifolium repens, white clover, defoliation, nodule respiration, N2, fixation, nitrogenase 相似文献
17.
Imsande, J. 1986. Inhibition of nodule development in soybeanby nitrate or reduced nitrogen.J. exp. Bot. 37: 348355. Nodulation of hydroponically grown soybean plants [Glycine max(L.) Merr.] is inhibited by continuous growth in the presenceof 4· mol m3 KNO3 The presence of 4·0 molm3 starter nitrate for 3-6 d during noduledevelopment, however, subsequently stimulates nodule dry weightaccumulation and nitrogenase activity. These stimulations occureven though 4· mol m3 nitrate temporarily delaysnodule development, i.e. the late steps of nodule developmentare reversibly inhibited by a short-term exposure to 4·0mol m3 nitrate. On the other hand, treatment with 4·0mol m3 nitrate in excess of 14 d significantly reducesnodule dry weight Thus, extended growth in the presence of 4·0mol m3 KNO3 seems to block both early and late stepsof nodule development. Nodulation of hydroponically grown soybeansis also inhibited by continuous growth in the presence of 2·0mol m3 (NH4)2SO4 This inhibition is not caused by acidityof the growth medium. On the other hand, nodule development6 d after inoculation with Rhizoblum japonicum is not delayedby a 7-d exposure to 2·0 mol m3 (NH4)2SO4 butis partially inhibited by a prolonged exposure to (NH4)2SO4Because repression of nodulation by 4·0 mol m3KNO3 is more severe than that by 2·0 mol m3 (NH4)2SO4and because ammonium taken up by the soybean plant is not activelyoxidized to nitrate, it is suggested that there are at leasttwo mechanisms by which nitrate utilization represses noduleformation in soybean. Key words: Glycine max, nitrogen, nitrogen fixation, nodulation 相似文献
18.
Biochemical Limitations to Carbon Assimilation in C3 Plants--A Retrospective Analysis of the A/Ci Curves from 109 Species 总被引:9,自引:0,他引:9
Species-specific differences in the assimilation of atmosphericCO2 depends upon differences in the capacities for the biochemicalreactions that regulate the gas-exchange process. Quantifyingthese differences for more than a few species, however, hasproven difficult. Therefore, to understand better how speciesdiffer in their capacity for CO2 assimilation, a widely usedmodel, capable of partitioning limitations to the activity ofribulose-1,5-bisphosphate carboxylase-oxygenase, to the rateof ribulose 1,5-bisphosphate regeneration via electron transport,and to the rate of triose phosphate utilization was used toanalyse 164 previously published A/Ci, curves for 109 C3 plantspecies. Based on this analysis, the maximum rate of carboxylation,Vcmax, ranged from 6µmol m2 s1 for the coniferousspecies Picea abies to 194µmol m2 s1 forthe agricultural species Beta vulgaris, and averaged 64µmolm2 s1 across all species. The maximum rate ofelectron transport, Jmax, ranged from 17µmol m2s1 again for Picea abies to 372µmol m2 s1for the desert annual Malvastrum rotundifolium, and averaged134µmol m2 s1 across all species. A strongpositive correlation between Vcmax and Jmax indicated that theassimilation of CO2 was regulated in a co-ordinated manner bythese two component processes. Of the A/Ci curves analysed,23 showed either an insensitivity or reversed-sensitivity toincreasing CO2 concentration, indicating that CO2 assimilationwas limited by the utilization of triose phosphates. The rateof triose phosphate utilization ranged from 4·9 µmolm2 s1 for the tropical perennial Tabebuia roseato 20·1 µmol m2 s1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm2 s1 across all species. Despite what at first glance would appear to be a wide rangeof estimates for the biochemical capacities that regulate CO2assimilation, separating these species-specific results intothose of broad plant categories revealed that Vcmax and Jmaxwere in general higher for herbaceous annuals than they werefor woody perennials. For annuals, Vcmax and Jmax averaged 75and 154 µmol m2 s1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm2 s1, respectively. Although these differencesbetween groups may be coincidental, such an observation pointsto differences between annuals and perennials in either theavailability or allocation of resources to the gas-exchangeprocess. Key words: A/Ci curve, CO2 assimilation, internal CO2 partial pressure, photosynthesis 相似文献
19.
The Effects of Low Concentrations of Sulphur Dioxide on Stomatal Conductance and Epidermal Cell Survival in Field Bean (Vicia faba L.) 总被引:4,自引:0,他引:4
Exposure of 3 week old field bean plants to concentrations ofSO2 from 50500 µg m-3 induced comparable 2025%increases in mean leaf diffusive conductance regardless of whetherthe diffusive conductances were obtained by porometric measurementor calculation from gas exchange data. The stomatal conductancesof the adaxial and abaxial leaf surfaces were both increasedby exposure to SO2. Microscopic examination of epidermal strips from control andpolluted plants revealed that the stomatal opening observedin treated plants was associated with a sharp reduction in theproportion of living epidermal cells adjacent to the stomata.The proportion of surviving adjacent epidermal cells was invariablysmaller on the lower epidermis and appeared to decrease as theSO2 concentration was raised from 50 to 500 µg m3.Although the guard cells appeared to be undamaged at concentrationsbelow 200 µg m3, structural disorganization ordeath of one or both guard cells was observed frequently ator above 500 µg m3. The results are discussed in relation to the controversy concerningthe effects of SO2 on stomatal aperture. 相似文献
20.
Wheeler T.R.; Hong T.D.; Ellis R.H.; Batts G.R.; Morison J.I.L.; Hadley P. 《Journal of experimental botany》1996,47(5):623-630
Winter wheat (Triticum aestivum L. cv. Hereward) was grown inthe field inside polyethylene-covered tunnels at a range oftemperatures at either 380 or 684 µmol mol1 CO2.Serial harvests were taken from anthesis until harvest maturity.Grain yield was reduced by warmer temperatures, but increasedby CO2 enrichment at all temperatures. During grain-filling,individual grain dry weight was a linear function of time fromanthesis until mass maturity (attainment of maximum grain dryweight) within each plot. The rate of progress to mass maturity(the reciprocal of time to mass maturity) was a positive linearfunction of mean temperature, but was not affected by CO2 concentration.The rate of increase in grain dry weight per ear was 2.0 mgd1 greater per 1 C rise, and was 8.0 mg d1 greaterat 684 compared with 380 µmol mol1 CO2 at a giventemperature. The rate of increase in harvest index was 1.0%d1 in most plots at 380 µmol mol1 CO2 andin open field plots, compared with 1.18% d1 in all plotsat 684 µmol mol1 CO2. Thus, the increased rateof grain growth observed at an elevated CO2 concentration couldbe attributed partly to a change in the partitioning of assimilatesto the grain. In contrast, the primary effect of warmer temperatureswas to shorten the duration of grain-filling. The rate of graingrowth at a given temperature and the rate of increase in harvestindex were only independent of the number of grains per earabove a critical grain number of 2324 grains per ear({small tilde}20 000 grains m2). Key words: Winter wheat, grain growth, temperature, CO2, harvest index, critical grain number 相似文献