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1.
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
2.
Diurnal temperature fluctuations induced change in soya bean-pod[Glycine max (L.) Merr.] carbon exchange rate (CER, where positiveCER represents CO2 evolution). CER appeared to depend linearlyon temperature. Linear regressions of CER on temperature interceptedthe temperature axis at 5°C (i.e. zero CER at 5°C).Slopes of these regressions (i.e. temperature sensitivity) changedover the season. The CER-temperature sensitivity coefficient,K, (calculated from observed values of CER. pod temperatureand temperature intercept) rose from less than 0·02 mgCO2 h1 pod1 °C1 during early pod-flll,peaked at over 0·04 mg CO2 h1 pod1 °C1at mid pod-fill, and then declined during late pod-fill andmaturation. Glycine max (L.) Merr., Soya bean, carbon exchange rate, temperature 相似文献
3.
Evidence for Essential Maintenance Respiration of Leaves of Xanthium Strumarium at High Temperature 总被引:3,自引:0,他引:3
Mesophyll resistance to photosynthetic carboxylation (r'm) wasused as a criterion for leaf integrity. It was measured, at25 °C, in the light, before and after periods of high temperature(3 h at 38 °C) in the dark. During the high temperatureperiods, respiration (RD) of attached leaves of Xanthium strumariumwas suppressed from 27%-36% by either low [O2] (1.04% or 0.21%v.v.) or high [CO2] (840 µl 11) in the ambientair. Neither treatment affected rates of RD or photo-respirationduring the second period at 25 °C. There was no significant increase of r'm when RD was not suppressedduring the high temperature treatment. When RD was suppressedat high temperatures, r'm increased from about 3s cm1before, to about 26 s cm1 after the high temperaturetreatment. The increase depended upon the degree of suppression. It is concluded that increased RD at high temperature in Xanthiumleaves is partly the result of an increase of energy demandingmaintenance. The subsequent rate of carbon dioxide fixationis reduced when this increase of maintenance-induced respirationis inhibited. 相似文献
4.
On the causes of interspecific differences in the growth-irradiance relationship for phytoplankton. II. A general review 总被引:5,自引:0,他引:5
The causes of interspecific differences in the µ-l relationshipare examined in the context of a mechanistic model which relatesµ to irradiance in terms of six factors:, kc photosyntheticquotient (PQ), Chl a:C, respiration and excretion. The effectof cell size on the light saturated growth rate is also considered.It is shown that photosynthetic efficiency and PQ exhibit remarkablylittle interspecific variability, and average 0.024 ±0.005 µg C(µg Chl a)1 h1 (µEm2 s1)1 and 1.5 ± 0.2 mol 02 molC1 (when NO3 is the nitrogen source) respectively.Two useful relationships were derived: (i) between growth efficiency,g and Chl a:C at µ. = 0; (ii) between the compensationintensity, Ic and the Chl a-specific maintenance respirationrate. Both relationships were independent of temperature anddaylength. Species best adapted to growth at low light werefound to exhibit high Chl a:C ratios and low maintenance respirationrates. As a group, diatoms were consistently the best adaptedfor growth at low irradiance. Chiorophytes, haptophytes, chrysophytesand cryptophytes were intermediate in their performance at lowirradiance. Dinoflagellates exhibited extreme diversity, withspecies spanning the spectrum from very good performance atlow irradiance to very poor. A new µmax-cell carbon relationshipis given based on growth rates normalized to 15°C. Evidenceis presented to show that noise in this relationship can besignificantly reduced by using only carbon-specific growth ratesand using only data for species grown at the same daylength. 相似文献
5.
Control of the Acclimation of Photosynthesis to Light and Temperature in Relation to Partitioning of Photosynthate in Developing Soybean Leaves 总被引:2,自引:0,他引:2
Photosynthetic acclimation was examined by exposing third trifoliolateleaves of soybeans to air temperatures of 20 to 30°C andphotosynthetic photon flux densities (PPFD) of 150 to 950µmolphotons m2 s1 for the last 3 d before they reachedmaximum area. In some cases the environment of the third leafwas controlled separately from that of the rest of the plant.Photosynthesis, respiration and dry mass accumulation were determinedunder the treatment conditions, and photosynthetic capacity,and dry mass and protein content were determined at full expansion.Photosynthetic capacity, the light-saturated rate of net carbondioxide exchange at 25°C and 34 Pa external partial pressureof carbon dioxide, could be modified between 21 and 35 µmolCO2 m2 s1 by environmental changes after leaveshad become exporters of photosynthate. Protein per unit leafmass did not differ between treatments, and photosynthetic capacityincreased with leaf mass per unit area. Photosynthetic capacityof third leaves was affected by the PPFD incident on those leaves,but not by the PPFD on other leaves on the plant. Photosyntheticcapacity of third leaves was affected by the temperature ofthe rest of the plant, but not by the temperature of the thirdleaves. Photosynthetic capacity was linearly related to carbondioxide exchange rate in the growth regimes, but not to daytimePPFD. At high PPFD, and at 25 and 30°C, mass accumulationwas about 28% of the mass of photosynthate produced. At lowerPPFD, and at 20°C, larger percentages of the photosynthateproduced accumulated as dry mass. The results suggest that photosynthatesupply is an important factor controlling leaf structural growthand, consequently, photosynthetic acclimation to light and temperature. Key words: Glycine max (L.) Merr., photosynthesis, temperature acclimation, light acclimation, photosynthate partitioning 相似文献
6.
CAMPBELL WILLIAM J.; ALLEN L. H. JR; BOWES GEORGE 《Journal of experimental botany》1990,41(4):427-433
Photosynthetic rates of outdoor-grown soybean (Glycine max L.Merr. cv. Bragg) canopies increased with increasing CO2 concentrationduring growth, before and after canopy closure (complete lightinterception), when measured over a wide range of solar irradiancevalues. Total canopy leaf area was greater as the CO2 concentrationduring growth was increased from 160 to 990 mm3 dm3.Photosynthetic rates of canopies grown at 330 and 660 mm3 CO2dm3 were similar when measured at the same CO2 concentrationsand high irradiance. There was no difference in ribulose bisphosphatecarboxylase/oxygenase (rubisco) activity or ribulose 1,5-bisphosphate(RuBP) concentration between plants grown at the two CO2 concentrations.However, photosynthetic rates averaged 87% greater for the canopiesgrown and measured at 660 mm3 CO2 dm3. A 10°C differencein air temperature during growth resulted in only a 4°Cleaf temperature difference, which was insufficient to changethe photosynthetic rate or rubisco activity in canopies grownand measured at either 330 or 660 mm3 CO2 dm3. RuBP concentrationsdecreased as air temperature during growth was increased atboth CO2 concentrations. These data indicate that the increasedphotosynthetic rates of soybean canopies at elevated CO2 aredue to several factors, including: more rapid development ofthe leaf area index; a reduction in substrate CO2 limitation;and no downward acclimation in photosynthetic capacity, as occurin some other species. Key words: CO2 concentration, soybean, canopy photosynthesis 相似文献
7.
Seasonal changes in the photosynthesis and primary productionof Microcystis aeruginosa Kütz. were investigated in LakeKasumigaura during 19811982. Microcystis always showeda light-saturated photosynthesis-light curve. Both Pmax andthe initial slope of the photosynthesis-light curve of Microcystisin early summer were very high, so it was concluded that Microcystisutilized both low and high light intensities efficiently. ThePmax of Microcystis was found to be a function of the watertemperature except in August and September. The linear regressionon the temperature-Pmax relationship discontinued at 11°C,where the Pmax value dropped; Microcystis did not photosynthesizebelow 4°C. The initial slope of the curve was also descendingbelow 11°C. It is suggested that Microcystis changes itsphysiological properties below 11°C. The highest value ofgross production calculated for M. aeruginosa was 5.4 gC m2d1 in July; the annual gross production was estimatedto be 300 gC m2year1 (i.e., 40% of the total primaryproduction in this lake). 相似文献
8.
The Carbon Economy of Rubus chamaemorus L. II. Respiration 总被引:1,自引:0,他引:1
Respiratory activity and seasonal changes in carbohydrate contentof the storage organs of Rubus chamaemorus L. have been investigated.Leaf dark respiration rate increases in a non-linear mannerfrom 0·7 mg CO2 evolved dm2 h1 at 0 °Cto 4·6 rng CO2 evolved dm2 hh1 at 30 °C.Root and rhizome respiration rates increase from 1 µ1O2 uptake g1 fresh weight h1 at 0.7 ° C to10 µ10, uptake g1 f. wt h1 at 20 °C.Rhizome carbohydrate reserves decline from a September peakof 33 per cent alcohol insoluble d. wt to 16 per cent in May. The circumpolar distribution of R. chamaemorus is discussedin relation to the evidence presented here and in the precedingpaper of the series. 相似文献
9.
Acclimation of single plants of Lolium temulentum to changing[CO2] was studied on plants grown in controlled environmentsat 20°C with an 8 h photoperiod. In the first experimentplants were grown at 135 µ;mol m2 s1 photosyntheticphoton flux density (PPFD) at 415µl l1 or 550µll1 [CO2] with some plants transferred from the lowerto the higher [CO2] at emergence of leaf 4. In the second experimentplants were grown at 135 and 500 µmol m2 s1PPFD at 345 and 575 µl l1 [CO2]. High [CO2] during growth had little effect on stomatal density,total soluble proteins, chlorophyll a content, amount of Rubiscoor cytochrome f. However, increasing [CO2] during measurementincreased photosynthetic rates, particularly in high light.Plants grown in the higher [CO2] had greater leaf extension,leaf and plant growth rates in low but not in high light. Theresults are discussed in relation to the limitation of growthby sink capacity and the modifications in the plant which allowthe storage of extra assimilates at high [CO2]. Key words: Lolium, carbon dioxide, photosynthesis, growth, stomatal density 相似文献
10.
Primary production was measured for 7 years, using the in situ14C-method in hypertrophic Hartbeespoort Dam, South Africa,to examine the influence of light and water temperature on theupper limit of Microcystis aeruginosa production. Water temperaturesvaried from 11 to >25°C and chlorophyll concentrationsreached 6500 mg m3. The maximum volumetric rate of production(Amax) was 12->8800 mg C m3 h1 with areal productions(A) of 69->3300 mg C m2 h1 for euphotic zonedepths of <0.58.4 m. The intrinsic parameters of phytoplanktonproduction (, Amax/B, Ik) indicated that the phytoplankton populationwas adapted to high light levels. Both Amax/B and Ik were correlatedwith temperature. Under optimal conditions, , the theoreticalupper limit of A, was calculated to be 2.8 g Cm2 h1,while the measured rate was 2.5 g Cm2 h1. Measuredareal rates exceeding were overestimated due to methodologicalproblems when working with Microcystis scums. Light and watertemperature interacted to yield high production rates: watertemperature through its direct effect on photosynthetic ratesand indirectly in the formation of diurnal mixed layers; lightindirectly through water temperature and directly through itsattenuation and induction of light-adapted physiology in Microcystis. 相似文献
11.
Acclimation of NO3 transport fluxes (influx, efflux)in roots of oilseed rape (Brassica napus L. cv. Bien venu) andtheir sensitivity to growth at low root temperature was studiedin relation to external NO3 supply, defined by constantconcentrations ranging from sub- to supra-optimal with respectto plant growth rate. Plants were grown from seed in flowingnutrient solutions containing 250 mmol m3 NO3at 17°C for 20d, and solution temperature in half the cultureunits was then lowered decrementally over 3 d to 7°C. Threedays later plants were supplied with NO3 at 1, 10, 100or 1000 mmol m3 maintained for 18 d. Dry matter productionwas decreased more by low root zone temperature than low [NO3]e. Root specific growth rates were inversely related to [NO3]eand shoot:root ratios increased with time at [NO3]e between101000 mmol m3. Net uptake of NO3 at 17°Cwas twice that at 7°C, and at both temperatures it doubledwith increasing [NO3]e between 110 mmol m3with further small increases at higher [NO3]e. Mean unitabsorption rates of NO3 between 06 d and 614d were linearly related (r2 of 0.790.99) to log10[NO].Steady-state Q10 (717°C) for uptake between 06d were 0.91, 1.62, 1.27, and 1.10, respectively, at [NO3]eof 1, 10, 100, and 1000 mmol m3, compared with correspondingvalues of 0.98, 1.38, 1.68, and 1.89 between 614 d. Thedata indicated that net uptake rates at 7 and 17°C divergedover time at high [NO3]e. Short-term uptake rates from1 mol m3 NO3 measured at 17°C were higherin plants grown with roots at 7°C than at 17°C; for7°C plants there was a strong inverse linear relationship(r2=0.94) between uptake rate and treatment log10 [NO3]ewhilst rates in 17°C plants were independent of prior [NO3]e. Rates of NO3 influx and efflux under different steady-stateconditions of NO3 supply and root temperature were calculatedfrom dilution of 15N added to culture solutions. Efflux wassubstantial relative to net uptake in all treatments, and wasinversely related to [NO3]e at 17°C but not at 7°C.Ratios of influx: efflux ranged from 1.62.9 at 17°Cand 1.31.8 at 7°C, indicating the proportionatelygreater impact of efflux at low root temperature. Ratios ofefflux: net uptake were 0.531.56 at 17°C and 1.213.58at 7°C. The apparent sensitivities of influx and effluxto steady-state root temperature varied with [NO3]e.Both fluxes were higher at 17°C than 7°C in the presenceof 1001000 mmol m3 NO3 but the trend wasreversed at 110 mmol m3 NO. Concentrations oftotal N measured in xylem exudate were at least 2-fold higherat 7°C compared with 17°C, attributable mainly to higherconcentrations of NO3 glutamine and proline. The resultsare discussed in terms of acclimatory and other responses shownby the NO3 transport system under conditions of limitingNO3 supply and low root temperature. Key words: Brassica napus, nitrate supply, efflux, influx, root temperature, xylem exudate 相似文献
12.
The Potential for Photoinhibition of Pinus sylvestris L. Seedlings Exposed to High Light and Low Soil Temperature 总被引:1,自引:0,他引:1
The effect of high light and root chilling on gas exchange,chlorophyll fluorescence, and bulk shoot water potential (shoot)was examined for Pinus sylvestris seedlings. Transferring plantsfrom low light (200 µmol m2s1, PAR) anda soil temperature of 15 °C to high light (850 µmolm2 s1) and 1 °C caused >90% decrease innet photosynthesis and leaf conductance measured at 350 mm3dm-3 CO2, and a decrease in the ratio of variable to maximumfluorescence (Fv/Fm) from 0.83 to 0.63. The decrease in Fv/Fmwas, however, only marginally greater than when seedlings weretransferred from low to high light but kept at a soil temperatureof 15 °C. Thus, photoinhibition was a minor component ofthe substantial decrease observed for net photosynthesis at1 °C soil temperature. The decrease in net photosynthesisand shoot at 1 °C was associated with an increase in calculatedintracellular CO2 concentration, suggesting that non-stomatalfactors related to water stress were involved in inhibitingcarbon assimilation. Measurements at saturating external CO2concentration, however, indicate that stomatal closure was thedominant factor limiting net photosynthesis at low soil temperature.This interpretation was confirmed with additional experimentsusing Pinus taeda and Picea engelmannii seedlings. Decreasesin gas-exchange variables at 5 °C soil temperature werenot associated with changes in shoot Thus, hormonal factors,localized decreases in needles or changes in xylem flux maymediate the response to moderate root chilling. 相似文献
13.
Ecological studies on the phytoplankton of Boknafjorden, western Norway. II. Environmental control of photosynthesis 总被引:2,自引:0,他引:2
Both predicted (incubator) and measured (in situ) 14C-assimilationrates were studied from February to November 1981 at three stationsin Boknafjorden, a deep silled fjord of western Norway. Sampleswere taken from different light depths within the euphotic zone.A high degree of conformity was found between the two approaches.Daily values of carbon assimilation integrated over the euphoticzone varied between 0.05 and 1.4 g C m2. Yearly primaryproduction varied between stations from 82 to 112 g C m2(120148 g C m2 when based on average light conditions).The light-saturation curve parameters B and PBmax ranged from0.0056 to 0.0537 mg C mg Chla1 h1 µE1m2 and from 0.7 to 8.5 mg C mg Chla1 h2 (in situassimilation numbers ranged from 0.9 to 9.3 mg C mg Chla1h1) respectively, which compare well with those publishedfrom the northwestern side of the Atlantic. The overall importanceof light in controlling photosynthesis throughout the year wasrevealed by the light utilization index , estimated to be 0.43mg C mg Chla1 E1 m2. The maximum quantum yieldwas encountered on August 17, with 0.089 mol CE1. Chla/Cratios above and below 0.010 were found to be typical for shade-and light-adapted cells respectively. Assimilation numbers andgrowth rates were linearly related only when considering light-adaptedcells. Consistent with the findings of this study, the applicabilityof IK, B and PBmax as indicators of light-shade adaptation propertiesshould be questioned. Maximum growth rates were encounteredduring an autumn bloom of the dinoflagellate Gyrodinium aureolum(1.0 doublings day1), while 0.70.8 doublings day1were found for a winter bloom (water temperature of 2°C)of the diatom Skeletonema costatum. No unambiguous temperatureeffect on assimilation number and growth of phytoplankton couldbe recognized in Boknafjorden. A tendency towards increasedassimilation numbers coinciding with increased water columnstability was revealed. The highest PBmax values were oftenencountered at almost undetectable nutrient concentrations.At least during summer this could be attributed to recyclingof nutrients by macro- and/or microzooplankton, responsiblefor a greater part of the primary production now being grazeddown. This study supports the convention that the depth of theeuphotic zone may extend considerably below the 1% light depth. 相似文献
14.
Aster kantoensis Kitam., an endangered plant species of thefamily Compositae, is a local endemic to the gravelly floodplainsof a few rivers in central Japan. The successful growth of A.kantoensis is mainly restricted to sparsely vegetated siteswhere, due to lack of continuous vegetation, high radiant energyinput results in stressful conditions with excessive light andheat. To reveal the ecophysiological characteristics which enablethe species to cope with such environmental stresses, we measuredleaf temperature, shoot architecture and photosynthetic andtranspirational responses together with the microclimate ofthe natural habitat. Even under sunny summer conditions, theleaf temperature of A. kantoensis was much lower (3539°C)than the soil surface temperature (max. 60°C). The relationshipbetween leaf position (height from the ground) and leaf temperatureshowed that the caulescent rosette form of A. kantoensis helpsavoid leaf overheating. Moreover, in situ gas exchange measurementsrevealed that the high transpirational capacity (as high as10 mmol H2O m-2s-1) was effective in controlling leaf temperature,as long as the soil water supply was not severely limited. Sinceit has effective mechanisms to avoid the multiple stresses indigenousto its gravelly floodplain habitat, A. kantoensis can maintaina high photosynthetic rate (up to 30 µmol CO2m-2s-1) withoutany midday depression under sunny summer conditions. Copyright2000 Annals of Botany Company Aster kantoensis Kitam., gravelly floodplain, high light stress, leaf temperature, photosynthesis, shoot architecture, transpiration 相似文献
15.
The plastochron index (PI) has been compared with leaf growthand biomass accumulation in young soya bean plants of severalcultivars that were grown in controlled environments with differentirradiance levels and durations, temperatures, and nitrogen(N) regimes. Increasing the photoperiod from 10 to 16 h day1 increasedthe plastochron rate (PR) and the proportion of axillary growth.Doubling the photosynthetic photon flux density (PPFD) to 1000µmol m2S1, increased PR and the proportionof roots to total plant weight, but decreased the proportionof stems plus petioles to total. In a series of experiments,the plants were grown in an 8 h photoperiod at constant temperaturesof 17, 20, 26 or 32 °C. As temperature increased, PR increased,but the duration of leaf expansion decreased. Leaves were largestat 20 and progressively smaller at 26, 32 and 17 °C. Biomasswas greatest for a given PI at 20 °C and decreased in theorder of 26, 32, and 17 °C. The proportion of axillary growthalso was greatest at 20 °C. When plants were grown in a15 h photoperiod at temperatures from 17.1 to 26.6 °C, leafsize continued to increase up to the highest temperature. At17 °C, the PR in the 15 h photoperiod (PPFD 390 µmol;m2S1) was about threefold greater than in 8 h(500 µmol m2 S1); biomass accumulation perday was about fivefold greater. Increasing N from 3 to 36 mMincreased PR about 10 per cent, altered biomass partitioningamong plant parts, and increased the biomass of the plants.The NO2 form of N markedly stimulated axillary growth as comparedwith the NH4+ form. Environment or cultivar had little influenceon the duration of leaf expansion in terms of PI. Cultivarsdid not differ consistently in biomass production and allocationin the different environments. Glycine max (L.) Merrill, soybean, soya bean, plastochron index, leaf development, growth analysis, partitioning, light, nitrogen, temperature 相似文献
16.
Dark uptake of inorganic 14C by offshore plankton was measuredat two depths at 36 stations in the Atlantic Ocean from 52°Sto 26°N, mainly along 30°W. The samples were incubatedfor 2 h with and without inhibition of biological activity withHgCl2. In addition, six time course experiments were performed.The mean dark uptake rate varied from 0.68 to 4.82 (µmolC m3 h1 over the transect and showed a significantpositive relationship with chlorophyll a. The dark uptake wasusually >5% of the maximum photosynthetic capacity (Pm),and higher values relative to Pm were associated with low valuesof Pm and not with high absolute dark values. A linear relationshipbetween dark uptake and Pm was found with a background value(y-axis intercept) of 0.51 (µmol C m3 h1and a slope of 0.77% of Pm. A major fraction of the dark signal,6680% of the total signal, persisted in bottles treatedwith HgCl2, indicating that most of the dark signal was independentof biological activity. Time course experiments showed a lineardark uptake with time for the first hours, whereafter the uptakeceased. At stations with low concentrations of inorganic nitrogen[>1 (µmol (NH4++NO3)], a second stage was observedafter 38 h, probably due to an increase in bacterialactivity. The results suggest three mechanisms for the darkvalue in short-term incubations in oligotrophic waters. A backgroundvalue independent of biomass and incubation time which was thedominant part of the dark signal in samples with very low phytoplanktonbiomass (>0.3 p-g Chi a 1"). Another important part was residualsof 14C associated with plankton, probably adsorbed to compoundsinside the cells. This fraction was dominant in short-term incubationsat chlorophyll concentrations >0.3 p.g Chi a H. Active uptakeby living cells (total minus HgCl2 uptake) wasonly a minor part of the dark signal in short-term incubations,but dominated at longer incubation time (>39 h), probablydriven by an increase in bacterial activity. A significant enhancementof the non-photosynthetic uptake of 14C was observed in light,probably associated with a carbon-concentrating mechanism inphytoplankton or light stimulation of ß-carboxylationactivity. The results strongly suggest that dark values shouldbe subtracted from the light uptake. This correction is particularlyimportant when photosynthetic rates are low, e.g. at low lightor in short-term incubations where a time-zero background becomesa significant part of the total uptake in light.
Present address: National Environmental Research Institute,Department of Marine Ecology and Microbiology, Frederiksborgvej399, PO Box 358, DK-4000 Roskilde, Denmark 相似文献
17.
HAAG-KERWER ANGELA; FRANCO AUGUSTO C.; LUTTGE ULRICH 《Journal of experimental botany》1992,43(3):345-352
Gas exchange and organic acid accumulation of the C3-CAM intermediateClusia minor L. were investigated in response to various day/nighttemperatures and two light regimes (low and high PAR). For bothlight levels equal day/night temperatures between 20°C and30°C caused a typical C3 gas exchange pattern with all CO2uptake occurring during daylight hours. A day/ night temperatureof 15°C caused a negative CO2 balance over a 24 h periodfor low-PAR-grown plants while high-PAR-grown plants showeda CAM gas exchange pattern with most CO2 uptake taking placeduring the dark period. However, there was always a considerablenight-time accumulation of malic acid which increased when thenight-time temperature was lowered and had its maximum (54 mmolm2) at day/night temperature of 30/15°C. A significantamount of malic acid accumulation (23 mmol m2) in low-PAR-grownplants was observed only at 30/15°C. Recycling of respiratoryCO2 in terms of malic acid accumulation reached between 2·0and 21·5 mmol m2 for high-PAR-grown plants whilethere was no significant recycling for low-PAR-grown plants.Both low and high-PAR-grown plants showed considerable night-timeaccumulation of citric acid. Indeed under several temperatureregimes low-PAR-grown plants showed day/night changes in citricacid levels whereas malic acid levels remained approximatelyconstant or slightly decreased. It is hypothesized that lowand high-PAR-grown plants have different requirements for citrate.In high-PAR-grown plants, the breakdown of citrate preventsphotoinhibition by increasing internal CO2 levels, whereas inlow-PAR-grown plants the night-time accumulation of citric acidmay function as an energy and carbon saving mechanism. Key words: C. minor, C3, CAM, citric acid, light intensity 相似文献
18.
Chilling Damage to Photosynthesis in Young Zea mays: I. EFFECTS OF LIGHT AND TEMPERATURE VARIATION ON PHOTOSYNTHETIC CO2 ASSIMILATION 总被引:4,自引:0,他引:4
Carbon dioxide and water vapour exchanges of the second leafof Zea mays in controlled environment cuvettes were measuredin an open gas-exchange system, during and following subjectionto low temperature stress. Photosynthetic CO2 assimilation (Fc)decreased markedly with decrease in leaf temperature so thatFc at 5 °C was c. 7% of Fc at 20 °C. Fc continued todecline if leaf temperature was maintained at 5 °C, andwhen returned to 20 °C the leaf could not regain its previousFc. This chill-induced reduction in the capacity of the leafto assimilate CO2 was proportional to the duration of the chilland increased with water vapour pressure deficit and photonflux density (In). Six hours at 5 °C decreased Fc on returnto 20 °C, relative to Fc prior to treatment, by c. 10% indarkness and by c. 50% in a photon flux density approachingfull-sunlight (Ip = 1.5 mmol m2 s1). The degreeof reduction in Fc following chill treatment showed an almostlinear dependence on both the length and temperature of thechill. Chill treatments resulted in a decrease in both stomataland mesophyll conductances. Examination of the responses ofFc to light and CO2 concentration suggested that chill damageto the capacity for CO2 assimilation resulted from effects onboth the light and CO2 limited processes within photosynthesis. Key words: Chilling, Photosynthesis, Zea mays, Light-temperature interaction 相似文献
19.
Environmental Influences on Carbon Recycling in a Terrestrial CAM Bromeliad, Bromelia humilis Jacq. 总被引:2,自引:0,他引:2
The effects of night-time temperature, leaf-to-air vapour pressuredeficit (VPD) and water stress on CO2 recycling in Bromeliahumilis Jacq. grown under two light and nitrogen regimes wereinvestigated. At night-time temperatures above 30°C, integratednet dark CO2 uptake was severely reduced and CO2 for malatesynthesis was mainly derived from dark respiration. At 35°C,up to 84% of the CO2 liberated by dark respiration was refixedinto malic acid. Below 30 °C only nitrogen deficient plantsshowed significant recycling. No significant differences wereobserved between high and low light grown plants in CO2 recycling.A doubling of leaf-to-air VPD from 7-46 Pa kPa1 to 15.49Pa kPa1 resulted in a 2- to 20-fold decrease in leafconductance and about 50 to 65% reduction in integrated darkCO2 uptake. However, about twice as much CO2 was recycled atthe higher VPD as in the lower. Ten days of water stress resultedin 80 to 100% recycling of respiratory CO2. Under high VPD andwater stress treatments, the amount of water potentially savedthrough recycling of CO2 reached 2- to 6-fold of the actualtranspiration. In general, nitrogen deficient plants had higherper cent recycling of respiratory CO2 in response to high night-timetemperature, increased VPD or water stress. The results emphasizethe ecological relevance of carbon recycling in CAM plants. Key words: Bromelia humilis, CAM, PPFD, dark respiration, temperature, VPD, water stress 相似文献
20.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown for 71 d in flowing nutrient solutions containingN as 10 mmol m3 NH4NO3, under artificial illumination,with shoots at 20/15°C day/night temperatures and root temperaturereduced decrementally from 20 to 5°C. Root temperatureswere then changed to 3, 7, 9, 11, 13, 17 or 25°C, and theacquisition of N by N2 fixation, NH4+ and NO3 uptakewas measured over 14 d. Shoot specific growth rates (d. wt)doubled with increasing temperature between 7 and 17°C,whilst root specific growth rates showed little response; shoot:root ratios increased with root temperature, and over time at11°C. Net uptake of total N per plant (N2 fixation + NH4++ NO3) over 14 d increased three-fold between 3 and 17°C.The proportion contributed by N2 fixation decreased with increasingtemperature from 51% at 5°C to 18% at 25°C. Uptake ofNH4+ as a proportion of NH4+ + NO3 uptake over 14 d variedlittle (5562%) with root temperature between 3 and 25°C,although it increased with time at most temperatures. Mean ratesof total N uptake per unit shoot f. wt over 14 d changed littlebetween 9 and 25°C, but decreased progressively with temperaturebelow 9°C, due to the decline in the rates of NH4+ and NO3uptake, even though N2 fixation increased. The results suggestthat N2 fixation in the presence of sustained low concentrationsof NH4+ and NO4 is less sensitive to low root temperaturethan are either NH4+ or NO3 uptake systems. White clover, Trifolium repens L. cv. Huia, root temperature, nitrogen fixation, ammonium, nitrate 相似文献