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1.
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
2.
CLIFFORD S. C.; STRONACH I. M.; MOHAMED A. D.; AZAM-ALI S. N.; CROUT N. M. J. 《Journal of experimental botany》1993,44(12):1763-1770
Stands of groundnut (Arachis hypogaea L.), a C3 legume, weregrown in controlled-environment glasshouses at 28 °C (±5°C)under two levels of atmospheric CO2 (350 ppmv or 700 ppmv) andtwo levels of soil moisture (irrigated weekly or no water from35 d after sowing). Elevated CO2 increased the maximum rate of net photosynthesisby up to 40%, with an increase in conversion coefficient forintercepted radiation of 30% (from 166 to 216g MJ1) in well-irrigated conditions, and 94% (from 064to 1·24 g MJ1) on a drying soil profile. In plantswell supplied with water, elevated CO2 increased dry matteraccumulation by 16% (from 13·79 to 16·03 t 1) and pod yield by 25% (from 2·7 to 3·4t ha1).However, the harvest index (total poddry weight/above-grounddry weight) was unaffected by CO2 treatment. The beneficial effects of elevated CO2 were enhanced under severewater stress, dry matter production increased by 112% (from4·13 to 8·87 t ha1) and a pod yield of1·34t ha1 was obtained in elevated CO2, whereascomparable plotsat 350 ppmv CO2 only yielded 0·22 t ha-1.There was a corresponding decrease in harvest index from 0·15to 0·05. Following the withholding of irrigation, plants growing on astored soil water profile in elevated CO2 could maintain significantlyless negative leaf water potentials (P<0·01) for theremainder of the season than comparable plants grown in ambientCO2, allowing prolonged plant activity during drought. In plants which were well supplied with water, allocation ofdry matter between leaves, stems, roots, and pods was similarin both CO2 treatments. On a drying soil profile, allocationin plants grown in 350 ppmv CO2 changed in favour of root developmentfar earlier in the season than plants grown at 700 ppmv CO2,indicating that severe waterstress was reached earlier at 350ppmv CO2. The primary effects of elevated CO2 on growth and yield of groundnutstands weremediated by an increase in the conversion coefficientfor intercepted radiation and the prolonged maintenance of higherleaf water potentials during increasing drought stress. Key words: Arachis hypogaea, elevated CO2, water stress, dry matter production 相似文献
3.
Yield-density Relationships: the Influence of Resource Availability on Growth and Self-thinning in Populations of Vulpia fasciculata 总被引:2,自引:0,他引:2
Monocultures of Vulpia fasciculata were grown over a wide rangeof densities to investigate the influence of crowding and nutrientsupply on growth and self-thinning. For a given time and densityseries the relationship between mean yield per plant (w) andthe density of survivors (N) could be described by the equation w= wm (1+aN)b. where wm is the yield of an isolated plant, a is the area requiredto achieve a yield of wm and b describes the effectiveness withwhich resources are taken up from the area. All three parametersincreased with time. Adding nutrients changed not only the rate at which the effectsof crowding occurred but also the intensity of crowding since wm = C(ab)D. where C and D are constants. The addition of nutrients resultedin an increase in the value of C. Such an increase means thata larger weight can be supported by a given area because theresources within that area are greater. During the early phases of growth, populations of V. fasciculataconformed to the 3/2 power law, w = cN3/2, butonly at very high densities with a plentiful supply of nutrients.However, once the maximum standing crop had been reached thetrajectory of the thinning line switched to a slope of justless than 1 when weight was ploted against density onlogarithmic scales. The intercept of the 3/2 thinningline was considerably higher (log c = 5.74) than those for mosttrees and forbs but was similar to those of a number of othergrasses. Vulpia fasciculata, dune fescue, yield-density models, self-thinning, density-dependence, nutrient supply 相似文献
4.
Relationship between Plant Weight and Growing Period for Vegetable Crops in the United Kingdom 总被引:1,自引:1,他引:0
GREENWOOD D. J.; CLEAVER T. J.; LOQUENS S. M. H.; NIENDORF K. B. 《Annals of botany》1977,41(5):987-997
A generalized equation is derived that relates total dry matterproduction to time from emergence for crops grown in the fieldwith adequate water and nutrients. It is: w+K1lnw+W0=K2t where w is the plant dry weight in t ha1, t is time indays after emergence, K2 and K1 are constants and W0 equals(w0+K1lnw0) where w0 is the value of w at the start ofthe growing period. The increases in the dry matter of 18 different types of vegetablecrop were measured at intervals during growth in the field.In every case the data fitted the equation very satisfactorilywith K1 set equal to 1 t ha1. The fitted values of K2were similar for many crops; those of W0 varied considerablybut were always similar to the values calculated from the individualseed weight and the plant population. Good fits were also obtainedwhen time in days was replaced with cumulative evaporation froman open water surface. It is concluded that the growth-time curves of many differentvegetable crops can be described by the same simple equationand that the variation between curves can be largely attributedto differences in seed weight and plant population. 相似文献
5.
Barley, ryegrass, and fodder radish were grown in flowing nutrientsolutions at four potassium concentrations, [Ke+], from 0.05to 4 mg I1. During the first 2 weeks after germinationthe response to [Ke+] (fodder radish > barley > ryegrass)depended on the potential relative growth rate, the ratio ofroot surface area to plant weight, and on the K+ flux into theroots. Subsequently, there was no effect of [Ke+] on growthrate within the range tested. The K+ flux decreased from 423? 1012 mol cm2 s1 in the first 2 weeksafter germination, when it was concentration-dependent, to 25? 1012 mol cm2 s1 after 45 weeks,when it became independent of [Ke+] down to 0.05 mg 11.The results explain the importance of high [Ke+] and rapid rootgrowth during the first 2 weeks after seed germination. 相似文献
6.
Carbon Dioxide and Ammonia Exchange in the Trachypogon Savannas of the Orinoco Llanos 总被引:1,自引:0,他引:1
Atmospheric carbon dioxide (CO2) and ammonia (NH2) exchangeswere determined in the Trachypogon savannas of the Orinoco Llanosusing the energy balance approach. Total dry mass and separatedry mass values of plant parts were used for a growth analysisof the community and for measurements of nitrogen content. Duringthe growth period, the net assimilation (P40) ranged from 0.102to 0.127 MJ m2 d1 (6.67.9 g dry mass m2d1). These figures were similar to mean crop growth ratemeasured using the mass balance approach (2.86.9 g drymass m2 d1). Analysis of the daily trend of theCO2 assimilated by the community showed a low total energy conversionof net photosynthesis (x = 0.7) compared with the values reportedfor tropical grasses. During the dry season, the community conserved71% of the maximum N accumulated during the previous wet season.Sixty-eight per cent of the community nitrogen content was lostas volatile NH3 from the community during the reproductive period.Results suggested that the predominant net NH3 efflux from thevegetation was determined by the low concentration of NH3 inthe atmosphere ( 1.8 µg m2) and the compensationconcentration point. However, N losses were balanced by annualnitrogen input to the community from precipitation and biologicalfixation. Thus, a redistribution rather than a loss of nitrogenseems to be occurring in the ecosystem. Carbon dioxide fluxes, ammonia fluxes, Trachypogon savannas, energy balance, growth analysis 相似文献
7.
The net assimilation rate (EA), relative growth-rate (Rw), andleaf-area ratio (FA) were measured for rape (Brassica napus),sunflower (Hetianthus annuus), and maize (Zea mays) at varioustimes of year in an arid climate, using young plants grown widelyspaced on nutrient culture. Multiple regression analysis accountedfor 9095 per cent of the variation in EA and RW in termsof two climatic variables: mean temperature and radiation receipt. EA rose linearly with radiation in all three species; increasein EA with temperature was greatest in maize and least (notsignificant) in rape. RWrose with radiation and temperature,the latter being the more important variable especially in coolweather; a temperature optimum was shown at 24° C in rape.FA rose with increase in temperature or decrease in radiation;its variation was due to change in leaf area/leaf weight ratherthan in leaf weight/plant weight. Multiple regression analyses can lead to faulty interpretationif the independent variables are correlated (as are climaticvariables in nature), but conclusions can be checked by controlled-environmentstudies in which climatic factors are not correlated. The presentconclusions are supported by such studies. The regression equations, coupled with average weather records,indicate seasonal cycles of growth parameters. EA is maximalnear midsummer and minimal near midwinter, following the radiationcycle. Maxima and minima in RW are about a month later, becauseRW is affected by the temperature cycle and this lags behindthe radiation cycle. FA is maximal in autumn and minimal inspring. EA is highest where radiation receipts near 750 cal cm2day1 coincide with high temperatures. This combinationoccurs only in clear midsummer weather at low latitudes, andis maintained over long periods only in arid regions. The fact that EA rose linearly with radiation suggests thatleaf water deficits arising under high radiation had littleeffect on EA and that saturating levels of light were very high. 相似文献
8.
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
9.
Water Relations of Chromium VI Treated Bush Bean Plants (Phaseolus vulgaris L. cv. Contender) under both Normal and Water Stress Conditions 总被引:1,自引:0,他引:1
BARCEL? JUAN; POSCHENRIEDER CHARLOTTE; GUNS? BENET 《Journal of experimental botany》1986,37(2):178-187
The effect of Chromium VI on leaf water potential (w), solutepotential (a), turgor potential (p) and relative water content(RWC) of primary and first trifoliatc leaves of Phaseolus vulgarisL. was studied under normal growth conditions and during anartificially induced water stress period in order to establishthe possible influence of this heavy metal on the water stressresistance of plants. Plants were grown on perlite with nutrientsolution containing 0, 10, 25, 50 or 100µg cm3 Cr as Na2Cr2O7.2H2O. The effect of Cr onwater relations was highly concentration dependent, and primaryand first trifoliate leaves were affected differently. The growthreducing concentrations of Cr (25, 50 and 100µg cm3) generally decreased s and w and increasedp in primary leaves. The 10 µg cm3 Cr treatmentdid not affect growth, but altered water relations substantially:in primary leaves w and p were increased and s decreased, whilein trifoliate leaves the effect was the opposite. All Cr treatedplants resisted water stress for longer than control plants.The higher water stress resistance may be due to the lower sand to the increased cell wall elasticity observed in Cr VItreated plants. Key words: Phaseolus vulgaris, Chromium VI, water stress, Richter plot 相似文献
10.
Single plants of white clover grown in controlled environments,and dependent for nitrogen on N, fixation, were defoliated at1 or 2 d intervals to 3, 2 and 1 expanded leaves per stolon(Expt 1), and to 1,0.5 (1 leaf on every alternate stolon) and0 expanded leaves per stolon (Expt 2), for 4350 days Plants adapted to severe defoliation by developing much smallerleaves with a slightly reduced specific leaf area, more stolons,a smaller proportion of weight in leaf, root and nodules anda greater proportion of weight in stolons. The daily yield (materialremoved by defoliation) of d. wt and nitrogen generally decreasedwith severity of defoliation, as did the residual plant weight.However, the efficiency of yield (daily yield/residualweight x 100) of dry matter and nitrogen was greater in themost severely defoliated treatments, attaining a maximum of56 % All plants adapted to the imposed defoliation regimes, howeversevere, with the result that even plants maintained withoutany fully expanded leaves invested a similar fraction of theirmetabolic resources in shoot and root as less severely defoliatedplants, and continued to grow and fix N2, albeit at a very reducedrate of 12 mg Nd11. The energetic cost of N2 fixation(acetylene reduction) remained constant in all treatments at31 mole CO2 mole C2H41, but there was some evidence thatrate of N2 fixation per unit of nodule weight declined in themost harshly defoliated treatment. Trifolium repens, white clover, continous defolation, growth, N2 fixation 相似文献
11.
A new model is proposed which relates the weight of plants totheir spatial arrangement. The weight of each plant is calculatedas the integral of the function f(r) = L(cr2 + 1)2 overan area allocated to it, r being distance from the plant, withL and c parameters to be specified. The model is thus concise,general, in that it can be used to describe the effects of anyspatial arrangement on plant weight, and the parameters L andc have a biological interpretation. It is also consistent withthe commonly-used relationship between plant weight (w) anddensity (p), w1 = a+bp. We show for carrots (Daucus carota L.) and red beet (Beta vulgarisL.), that the mean weights fitted by the model agree as wellwith the experimentally observed mean plot weight as those fittedby more complex models with more parameters, some of which arenot as general. We show also that the parameter c can be predictedfrom the time from sowing to harvest, with good results whentested on sets of data independent of those to which the modelhad been fitted. The assumptions on which the model is based,its application, and extensions to it are discussed. Crop yield, plant density, plant arrangement, carrot, Daucus carota L., red beet, Beta vulgaris L., soya bean, Glycine max L., mathematical model 相似文献
12.
Knight, S. L. and Mitchell, C. A. 1988. Effects of CO2 and photosyntheticphoton flux on yield, gas exchange and growth rate of Lactucasativa L. Waldmanns Green'.J. exp. Bot.39: 317328. Enrichment of CO2 to 46 mmol m3 (1 000 mm3 dm3)at a moderate photosynthetic photon flux (PPF) of 450 µmolm2 s1 stimulated fresh and dry weight gain oflettuce leaves 39% to 75% relative to plants at 16 mmol m3CO2 (350 mm3 dm3). Relative growth rate (RGR) was stimulatedonly during the first several days of exponential growth. ElevatingCO2 above 46 mmol m3 at moderate PPF had no further benefit.However, high PPF of 880900 µmol m2 s1gave further, substantial increases in growth, RGR, net assimilationrate (NAR) and photosynthetic rate (Pn), but a decrease in leafarea ratio (LAR), at 46 or 69 mmol m3 (1000 or 1500 mm3dm3) CO2, the differences being greater at the higherCO2 level. Enrichment of CO2 to a supraoptimal level of 92 mmolm3 (2000 mm3 dm3) at high PPF increased leaf areaand LAR, decreased specific leaf weight, NAR and Pn and hadno effect on leaf, stem and root dry weight or RGR relativeto plants grown at 69 mmol m3 CO2 after 8 d of treatment.The results of the study indicate that leaf lettuce growth ismost responsive to a combination of high PPF and CO2 enrichmentto 69 mmol m3 for several days at the onset of exponentialgrowth, after which optimizing resources might be conserved. Key words: Photosynthesis, relative growth rate, CO2 enrichment 相似文献
13.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown as simulated swards for 71 d in flowing nutrientsolutions with roots at 11 C and shoots at 20/15 C, day/night,under natural illumination. Root temperatures were then changedto 3, 5, 7, 11, 13, 17 or 25 C and the total N2, fixation over21 d was measured in the absence of a supply mineral N. Alltreatments were subsequently supplied with 10 mmol m2NO2 in the flowing solutions for 14 d, and the relativeuptake of N by N2, fixation and NO3 uptake was compared.Net uptake of K+ was measured on a daily basis. Root temperature had little effect on root d. wt over the 35-dexperimental period, but shoot d. wt increased by a factor of3.5 between 3 and 25 C, with the sharpest increase occurringat 711 C. Shoot: root d. wt ratios increased from 25to 68 with increasing temperature at 725 C. N2-fixationper plant (in the absence of NO2 ) increased with roottemperature at 313C, but showed little change above13 C. The ratios of N2 fixation: NO2 uptake over 14d (mol N: mol N) were 0.470.77 at 37 C, 092154at 1117 C, and 046 at 25 C, reflecting the dominanceof NO3 uptake over N2 fixation at extremes of high andlow root temperature. The total uptake of N varied only slightlyat 1125 C (095110 mmol N plant1),the decline in N2 fixation as root temperature increased above11 C was compensated for by the increase in NO 3 uptake.The % N in shoot dry matter declined with decreasing root temperature,from 32% at 13 C to 15% at 3 C. In contrast, concentrationsof N expressed on a shoot water content basis showed a modestdecrease with increasing temperature, from 345 mol m3at 3 C to 290 mol m3 at 25 C. Trifolium repens L, white clover, root temperature, N2 fixation, potassium uptake, nitrate uptake, flowing solution culture 相似文献
14.
Studies on the Movement of Water Through Apple Trees 总被引:12,自引:0,他引:12
Resistances to the flow of water through young potted appletrees were estimated by measuring the transpiration rate oftrees with and without root systems. Root system resistanceswere obtained by difference. Whole-plant resistances were ofthe order 10 x 1013 Pa s m3 and there was some evidencethat root resistances (Rr) varied with transpiration rate; theratio Rr:Rx (where Rx is resistance to water flow in the stemsystem) altered from 2:1 at relatively high transpiration ratesto 1:1 at lower rates. The trunk of a 9-year-old orchard tree (trunk diameter {smalltilde}7 cm, height {small tilde}2.5 m) was cut under water andestimates of the flow resistances in this tree were obtained.These were much lower than the resistances to flow in the pottedtrees. Capacitance (defined as the change in stored water content perunit change in plant water potential) values were calculatedfor the small trees and the large tree from measurements ofweight and water potential changes after the trees were removedfrom water. They were very similar on a weight basis (approx.2.0 x 108 kg kg1 Pa1). Leaf capacitancevalues ({small tilde}1 x 108 kg Pa1 m2)were also obtained. Stomatal conductances decreased with water potential and increasedwith short-wave radiation, but the relationships were not definitive.Estimates of boundary layer conductance in a greenhouse (verylow wind speeds) were of the same order ({small tilde}5 mm s1)as values obtained previously. 相似文献
15.
Effect of Salinity on Growth, Nodulation and Nitrogen Yield of Chickpea (Cicer arietinum L.) 总被引:2,自引:0,他引:2
Chickpea cultivar ILC 482 was inoculated with salt-tolerantRhizobium strain Ch191 in solution culture with different saltconcentrations added either immediately with inoculation or5 d later. The inhibitory effect of salinity on nodulation ofchickpea occurred at 40 dS m1 (34.2 mol m3 NaCl)and nodulation was completely inhibited at 7 dS m1 (61.6mol m3 NaCl); the plants died at 8 dS m1 (71.8mol m3 NaCl). Chickpea cultivar ILC 482 inoculated with Rhizobium strain Ch191spcstrwas grown in two pot experiments and irrigated with saline water.Salinity (NaCl equivalent to 14 dS m1) significantlydecreased shoot and root dry weight, total nodule number perplant, nodule weight and average nodule weight. The resultsindicate that Rhizobium strain Ch191 forms an infective andeffective symbiosis with chickpea under saline and non-salineconditions; this legume was more salt-sensitive compared tothe rhizobia, the roots were more sensitive than the shoots,and N2 fixation was more sensitive to salinity than plant growth. Key words: Cicer arietinum, nodulation, N2 fixation, Rhizobium, salinity 相似文献
16.
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
17.
Accumulation of dry weight was measured in plant parts of meadowfescue (Festuca pratensis Huds.) that was grown at 16/11 °Cor 26/21 °C and with 20 or 60 nE cm2 s1 photosyntheticallyactive radiation. Plants reached anthesis about 3 weeks laterat 16/11 °C than at 26/21 °C and had then a higher proportionof dry weight in inflorescences and less in leaf blades. Growthtemperature had little effect on CO2 exchange rate (CER) butplants grown at 60 nE cm2 s1 had higher CER thanthose grown at 20 nE cm2 s1. The concentration of water-soluble carbohydrates (WSC) at similargrowth stages was usually higher at 16/11°C than at 26/21°C.High radiation also led to higher WSC in stem and leaf tissue.Root tissue changed least and WSC did not exceed 10% of dryweight during the experiment. In all tissues, when WSC was high,the fructans were distributed into a group with a high degreeof polymerization (DP) and another with a low DP. The low DPgroup included sucrose, reducing sugars and fructans up to about20 units long. An apparent threshold concentration of WSC wasnecessary for synthesis of the high DP fructans. This concentrationwas near 12% for leaf tissue, about 6% for stem base tissue,and 2.5% for root tissue. The average apparent DP of the highDP fructan group was 43 to 50 for leaf tissue, 31 to 93 forstem base tissue, and 27 to 31 for roots. These characteristicsappeared to be mostly tissue dependent with less effect fromtemperature and radiation. Key words: Fructans, Meadow fescue, Environmental effects, Dry weight distribution 相似文献
18.
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
19.
Effect of Elevated CO2 on the Photosynthesis, Respiration and Growth of Perennial Ryegrass 总被引:1,自引:0,他引:1
Single, seed-grown plants of ryegrass (Lolium perenne L. cv.Melle) were grown for 49 d from the early seedling stage ingrowth cabinets at a day/night temperature of 20/15 C, witha 12 h photoperiod, and a CO2 concentration of either 340 or680µI 11 CO2. Following complete acclimation tothe environmental regimes, leaf and whole plant CO2 effluxesand influxes were measured using infra-red gas analysis techniques.Elevated CO2 increased rates of photosynthesis of young, fullyexpanded leaves by 3546% and of whole plants by morethan 50%. For both leaves and whole plants acclimation to 680µI1 CO2 reduced rates of photosynthesis in bothCO2 regimes, compared with plants acclimated to 340µll1. There was no significant effect of CO2 regime onrespiration rates of either leaves or whole plants, althoughleaves developed in elevated CO2 exhibited generally lower ratesthan those developed in 340µI I1 CO2. Initially the seedling plants in elevated CO2 grew faster thantheir counterparts in 340µI I1 CO2, but this effectquickly petered out and final plant weights differed by onlyc. 10%. Since the total area of expanded and unexpanded laminaewas unaffected by CO2 regime, specific leaf area was persistently1340% lower in elevated CO2 while, similarly, root/shootratio was also reduced throughout the experiment. Elevated CO2reduced tissue nitrogen contents of expanded leaves, but hadno effect on the nitrogen contents of unexpanded leaves, sheathsor roots. The lack of a pronounced effect of elevated CO2 on plant growthwas primarily due to the fact that CO2 concentration did notinfluence tiller (branch) numbers. In the absence of an effecton tiller numbers, any possible weight increment was restrictedto the c. 2.5 leaves of each tiller. The reason for the lackof an effect on tillering is not known. Key words: Lolium perenne, ryegrass, elevated CO2, photosynthesis, respiration, growth, development 相似文献
20.
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