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1.
The economy of carbon in nodulated white lupin (Lupinus albusL.) was studied in terms of consumption of net photosynthatein nitrogen fixation, in maintenance of respiration, and inthe production of dry matter and protein. Net photosynthesisrose to a maximum in early fruiting and then fell abruptly dueto shedding of leaves. Nodulated roots acquired translocateequivalent to 51% of the plant's net photosynthate, 78% of thecarbon of this translocate being respired, 10% entering drymatter, and 12% returning to the shoot attached to productsof nitrogen fixation. Nodules utilized 4?0–6?5 g C infixing 1 g nitrogen. Photosynthate was utilized most effectivelyfor nitrogen fixation in late vegetative growth. Fruits sequestered16% of the plant's net photosynthate, shoot night respiration17%, and dry matter formation in shoot vegetative parts 22%.Averaged over growth, 9?9 g net photosynthate was required toproduce 1 g seed dry matter and 31 g net photosynthate to produce1 g seed protein. Budgets for utilization of the carbon of netphotosynthate were constructed for 10 d intervals of the plant'sgrowth cycle. Feeding of shoots with 14CO2 resulted in radiocarbonbecoming partitioned approximately as predicted by these budgets.The dependence of root respiration on recent photosynthate wasassessed by following the time course of release of 14CO2 tothe rooting medium of the 14CO-labelled plants.  相似文献   

2.
Autoradiography and liquid scintillation techniques were usedto trace the pattern of photoassimilate translocation in twoperennial forest herbs, Aster acuminatus Michx. and Clintoniaborealis (Ait.) Raf. Vegetative shoots of C. borealis emergeearly each spring from the growing apices of a long-lived rhizomesystem. Vegetative shoots of A. acuminatus emerge in late springfrom rhizomes that decay within 2 years. In both species rametssurvive for only one growing season. Any connected plants aresisters. Mature leaves of these two species were exposed for1 h periods to 14CO2 during spring and summer. Radioactivitycould subsequently be detected in exposed leaves (16–84per cent, depending on the season), adjacent above ground plantparts (0.7–23 per cent), roots and rhizomes (4.9–84per cent) and, when present, flowers (4–8.5 per cent).Old rhizomes of C. borealis are prominent storage sites forphotosynthate. In A. acuminatus, no significant translocationbetween sister ramets (i.e. above ground shoots connected bya common rhizome) was observed. In C. borealis, there was small,but consistent translocation between sister ramets (0.2–4per cent). Disturbance of unexposed sister ramets by defoliation,shading or herbivory increased the flow of photoassimilatesto disturbed parts in C. borealis, but not in A. acuminatus.Based on the absence of translocation flow, ramets of A. acuminatusmay be regarded as physiologically independent. Connected rametsof C. borealis show physiological integration. These resultsare correlated with ecological differences between the two species. Aster acuminatus, Clintonia borealis, translocation, ramet, vegetative reproduction, forest herb  相似文献   

3.
Potted white pine (Pinus strobus L.) seedlings were grown ingravel either in outdoor cold frames or in growth chambers.They were watered every second day with a salt solution containingdifferent amounts of nitrogen and phosphorus. After 13 weeksof growth individual seedlings were illuminated separately for8 h in the presence of 14CO2 and the rates of their apparentphotosynthesis, respiration, and translocation of recent 14C-photosynthateto their roots were observed. Roots were extracted with 80 percent ethanol and the nature of various 14C compounds in theextract was determined by paper chromatography. The best over-all growth of plants, mycorrhizal development,apparent photosynthesis, and translocation of recent photosynthateto the roots were observed in plants grown at the intermediatelevels of N and P nutrition. Sucrose was always the dominant form in which recently translocated14C occurred in the roots, although with increased nitrogensupply there was increased hydrolysis of sucrose to hexosesand appearance of 14C in the amino- and organic acids.  相似文献   

4.
Barley and rice, at the early tillering stage, were grown inaerated nutrient solutions (> 7 mg O2 l–1) and transferredto solutions of low O2 concentrations (< 0.5 mg l –1). For barley, low O2 concentrations during the first 5 days severelyinhibited growth of seminal roots had less effect on nodal roots,and did not reduce shoot growth. Longer exposure to low O2 concentrationsreduced shoot as well as root growth. Sugar concentrations inroots and shoots increased within 7 h after transfer of plantsto low O2 concentrations. After 5 days at low O2 concentrationssugar concentrations were very high in fast growing nodal rootsand in shoots, as well as in the slower growing seminal roots. In rice, low O2 concentrations increased sugar levels of rootsduring summer, but not during winter. In summer, the highersugar levels at low O2 concentrations persisted throughout adiurnal cycle. In root apices, sugar concentrations were increasedby low O2 concentrations, even though the experiment was donein winter and the bulk of the root system showed no differencein sugar levels. The data indicate that sugar accumulation, at low O2 concentrations,is caused by reduced growth and also that even apices of rootsgrown at low O2 concentrations have sufficient substrates forrespiration. Hordeum vulgare L, barley, Oryza sativa L, rice, sugar accumulation, oxygen concentration  相似文献   

5.
The effects of three ranges of CO2 concentration on growth,carbon distribution and loss of carbon from the roots of maizegrown for 14 d and 28 d with shoots in constant specific activity14CO2 are described. Increasing concentrations of CO2 led toenhancement of plant growth with the relative growth rate (RGR)of the roots affected more than the RGR of the shoots. Between16% and 21% of total net fixed carbon (defined as 14C retainedin the plant plus 14C lost from the root) was lost from theroots at all CO2 concentrations at all times but the amountsof carbon lost per unit weight of plant decreased with time.Possible mechanisms to account for these observations are discussed. Key words: Growth, Roots, Carbon loss, [CO2]  相似文献   

6.
Kouchi, H. and Higuchi, T. 1988. Carbon flow from nodulatedroots to the shoots of soybean {Glycine max L. Merr.) plants:An estimation of the contribution of current photosynthate toureides in the xylem stream.–J. exp. Bot. 39: 1015–1023. Well-nodulated, water-cultured soybean plants were allowed toassimilate 13CO2 at a constant specific activity for 10 h andthe 13C-labelling of total carbon and ureides in xylem sap wasinvestigated. Labelled carbon appeared very rapidly in the xylem stream. Percentageof labelled carbon (relative specific activity, RSA) in xylemsap was 18% at 2 h after the start of 13CO2 assimilation andreached 53% at the end of the 10 h assimilation. The amountof labelled carbon exported from nodulated roots to the shootsvia the xylem during the 10 h labelling period accounted for33% of total labelled carbon imported into the nodulated roots.Ureides (allantoin and allantoic acid) in xylem sap were stronglydependent on currently assimilated carbon. The RSA of ureidesin xylem sap had reached 83% at the end of the assimilationperiod. Labelled carbon in ureides accounted for 51% of totallabelled carbon returned from nodulated roots to the shootsvia the xylem during the 10 h assimilation period. A treatmentwith 20 mol m–3 nitrate in the culture medium for 2 ddecreased the ureide concentration in the xylem sap slightly,but greatly decreased the RSA of ureides. By comparing the data with the results of analysis of the xylemsap of nodule-detached plants, it was concluded that the majorityof labelled carbon exported to the xylem stream from noduleswas in ureide form. A considerable amount of carbon was alsoreturned from roots to shoots via the xylem stream but it wasmore dependent on (non-labelled) carbon reserved in the roottissues. Key words: Soybean(Glycine max L.), root nodule, carbon partitoning, 13CO2 assimilation, xylem  相似文献   

7.
Carob seedlings were grown hydroponically for 9 weeks under360 and 800 µl l-1CO2. One of two nitrogen sources, nitrateor ammonium, was added to the nutrient medium at concentrationsof 3 mol m-3. Root systems of the developing plants suppliedwith nitrate compared to those supplied with ammonium were characterizedby:(a)more biomass on the lower part of the root;(b)fewer lateralroots of first and second order;(c)longer roots;(d)higher specificroot length;(e)a smaller root diameter. The morphology of theroot systems of nitrate-fed plants changed in the presence ofelevated carbon dioxide concentrations, resembling, more closely,that of ammonium-fed plants. Total leaf area was higher in ammonium-than in nitrate-fed plants. Nitrate-fed plants had greater totalleaf area in the presence of high carbon dioxide than in normalCO2, due to an increase in epidermal cell size that led to developmentof larger leaflets with lower stomatal frequency. The observedchanges in the morphology of roots and shoots agreed with theresults observed for total biomass production. Nitrate-fed plantsincreased their biomass production by 100% in the presence ofelevated CO2compared to 15% in ammonium-fed plants, indicatingthat the response of carob to high CO2concentrations is verydependent on the nitrogen source. Under elevated CO2, nitrate-grownplants had a larger content of sucrose in both roots and shoots,while no significant difference was observed in the contentof sucrose in ammonium-grown plants, whether in ambient or enrichedcarbon dioxide. Hence, the differences in soluble carbohydratecontents can, at least partly, account for differences in rootand shoot morphology.Copyright 1997 Annals of Botany Company Ceratonia siliquaL.; carob; ammonium; carbohydrate; carbon dioxide; nitrate; morphology; sucrose  相似文献   

8.
HARRIS  D.; DAVY  A. J. 《Annals of botany》1988,61(2):147-157
We report physiological aspects of the response of seedlingsof the strandline grass Elymus farctus to short-term burialwith sand. Seedlings were buried at the two-leaf stage for oneweek and compared with non-buried controls - before, duringand after burial. Photosynthetic CO2 uptake was measured byinfrared gas analysis and carbon translocation from the youngestexpanded leaf was monitored after exposure to 14CO2. The concentrationsof water-soluble carbohydrate, and total nitrogen, phosphorusand potassium in component organs were determined. Net photosynthetic capacity was almost completely inhibitedby 5 d of burial. However, plants uncovered after 7 d of burialrecovered full photosynthetic competence within 24 h. Therewas a sharp, sustained depression in the water-soluble carbohydrateconcentration of the roots and stems after burial, whereas leaves1–3 had much higher concentrations than non-buried plantsfor up to 20 d after uncovering. Burial virtually suppressedthe translocation of 14C to stem, roots and expanding leaves,and this effect persisted even after full recovery of net photosynthesis.The proportional allocation of total N, P and K to leaves wasincreased after burial, mainly at the expense of the roots.Changes both in nutrient concentration and in the relative massesof organs contributed to this effect. The apparent reversal of the normal source-sink relationshipsfor carbohydrate between photosynthetic and non-photosyntheticorgans, and the differential allocation of inorganic nutrients,may contribute to the maintenance of photosynthetic capacityduring burial. The rapid recovery of net photosynthesis afterre-exposure suggests that these responses may be advantageousfor survival of E. farctus seedlings in the early stages ofgrowth in a physically unstable and unpredictable environment. Sand burial, photosynthesis, translocation, nutrient allocation, Elymus farctus, sand couch grass  相似文献   

9.
Gould, R. P. and Mansfield, T. A. 1988. Effects of sulphur dioxideand nitrogen dioxide on growth and translocation in winter wheat.—J. exp. Bot 39: 389–99 Winter wheat (Triticum aestivum L. cv. Avalon) was grown undersimulated autumn conditions for 4 weeks and exposed to a mixtureof SO2 and NO2. Biomass was measured after 2, 3 and 4 weeksand the flag leaves of sample plants were labelled with 14CO2.Biomass yields revealed an increase in shoot-to-root ratiosunder polluted conditions. The labelling experiments showedthat less assimilate was transported to the roots, whilst morewas allocated to the younger components of the plant. It appearedthat NO2 and SO2 also caused labelled photosynthate to be retainedin the labelled leaf. Reducing the photon flux exacerbated theeffects of SO2 and NO2 as indicated by changes in biomass andby the distribution of 14C. Key words: Wheat, SO2, NO2, growth, translocation  相似文献   

10.
The loss of organic material from the roots of forage rape (Brassicanapus L.,) was studied by pulse-labelling 25-d-old non-sterilesand-grown plants with 14CO2. The distribution of 14C withinthe plant was measured at 0, 6 and 13 d after labelling whilst14 C accumulating in the root-zone was measured at more frequentintervals. The rates of 14C release into the rhizosphere, andloss of 14CO2 from the rhizosphere were also determined. Thesedata were used to estimate the accumulative loss of 14C fromroots and loss respiratory 14CO2 from both roots and associatedmicro-organisms. Approximately 17-19% of fixed 14CO2 was translocatedto the roots over 2 weeks, of which 30-34% was released intothe rhizosphere, and 23-24% was respired by the roots as 14CO2. Of the 14C released into the rhizosphere, between 35-51%was assimilated and respired by rhizosphere micro-organisms.Copyright1993, 1999 Academic Press Brassica napus L., carbon loss, carbon partitioning, microbial nutrition, microbial respiration, forage rape, pulse-labelling, rhizodeposition, root respiration, sand culture  相似文献   

11.
The effects of elevated CO2and temperature on the growth, resourceacquisition and resource allocation of small birch seedlings(Betula pendula Roth.) were examined under conditions of non-limitingsoil, water and nutrient supply. Seedlings were planted in potsand placed in controlled environment chambers either under normalambient conditions (CON), or in the presence of elevated CO2(approx.700 µmol mol-1; Elev. C), elevated temperature (approx.3 °C above the outside ambient temperature; Elev. T) ora combination of elevated CO2and elevated temperature (Elev.C + T). Both Elev. C and Elev. T significantly increased biomassaccumulation, but the extent of the increase depended greatlyon the stage of development of the seedlings. Furthermore, thetheoretically expected positive effect of the warmer temperatureon the CO2-induced stimulation of growth was not observed. Byanalysing resource acquisition (i.e. CO2 , nitrogen and wateruptake), seedling development, leaf area production and theallocation pattern, it was deduced that the CO2-stimulated increasein biomass resulted mainly from the initial ‘fertilization’effect of CO2while the temperature-induced increase in biomassstemmed from higher net carbon intake during the middle andlatter parts of the growing season achieved by virtue of theincreased leaf area and larger photosynthetic capacity. Thelack of positive stimulation by temperature under Elev. C +T may be related in part to (1) CO2-induced acceleration ofseedling development, which led to a small or no response toCO2enrichment and lower leaf area production during the latterpart of the growth season, and (2) a cumulative delay in theresponse of growth to the warmer temperature, which did notincrease net carbon intake when the seedlings were at a juvenilestage. Neither Elev. C nor Elev. T altered the root:shoot ratioduring early growth, but Elev. C increased it during the latterpart of the growth season while Elev. T decreased it, possiblyon account of a change in leaf area retention. Finally, thenitrogen and water use efficiencies of seedlings at differentstages of development are discussed. Copyright 2001 Annals ofBotany Company Photosynthesis, growth, resource acquisition and allocation, elevated CO2and temperature, Betula pendula Roth  相似文献   

12.
Kouchi, H., Akao, S. and Yoneyama, T. 1986. Respiratory utilizationof 13C-labelled photosynthate in nodulated root systems of soybeanplants.—J. exp. Bot. 37: 985–993. An improved method for the measurement of respiratory utilizationof current photosynthate in the nodulated root system of water-culturedsoybean (Glycine max L.) plants was developed using a steady-state13CO2 labelling technique. Well-nodulated plants at the latevegetative stage were allowed to assimilate 13CO2 for 10 h incontinuous light at a constant CO2 concentration with a constant13C abundance. The respiratory evolution of 13CO2 from rootsand nodules was measured continuously throughout the periodof 13CO2 assimilation and during a subsequent 36 h chase periodby using a differential infrared 13CO2 analyser. The plantswere grown with nitrogen-free or (15 mmol dm–3)-containing culture solution for 3 d before13CO2 assimilation. In plants grown without , nodule respiration averaged 69% of the total respiration of the undergroundparts over the full experimental period and the CO2 respiredreached an apparent isotopic equilibrium at 80–85% labellingafter initiating 13CO2 assimilation. By contrast, the CO2 respiredfrom the roots did not reach an isotopic equilibrium and labellingwas only 56% at the end of exposure to 13CO2 These findingsdemonstrated that nodule respiration is strongly dependent onrecently assimilated carbon compared with root respiration. Plants supplied with in the culture solution showed a decreased rate of nodule respirationand a slightly increased rate of root respiration. The extentsand time courses of labelling of respired CO2 from both theroots and nodules were similar in the presence and absence of except that the maximum level of labelling of CO2 derived from nodule respiration in plantswith was significantly higher (about 91%) than for plants growing without . Key words: Soybean (Glycine max L.), nodule respiration, 13CO2, assimilation, carbon partitioning  相似文献   

13.
Growth and production of the temperate C4 species Cyperus longusL. was measured throughout a growing season in an establishedplot in Eastern Ireland. The maximum standing live biomass reachedwas 2·5 kg m–2. Estimates of unit leaf rate (ULR)and leaf area index (LAI) were made. The product of these quantitiesgave the crop growth rate (CGR) each week. C. longus was foundto maintain high values of LAI throughout the summer, with amaximum value of about 13 in early August. CGR reached a peakin early July. The optimum LAI was 11·6. Temperaturesat five levels in the plant canopy, and the amount of solarradiation intercepted by the canopy were measured continuouslyduring the summer. The mean daily rate of leaf extension waspositively correlated with the mean daily air temperature abovethe canopy but the temperature coefficient of the process waslow compared with other temperate species. The percentage ofsolar radiation intercepted by the canopy increased rapidlyin early summer, and canopy closure had occurred by mid-June.Rates of net photosynthesis were measured on young and old leafmaterial in situ at the time of peak LAI. In young leaves themaximum rates of net photosynthesis were higher than those publishedfor a range of temperate C3 species, but similar to those foundin another temperate C4 species, Spartina townsendii. Key words: C4 photosynthesis, leaf growth, productivity  相似文献   

14.
Three-month-old Carrizo citrange (hybrid of Citrus sinensisL. OsbeckxPoncirus trifoliata Blanco) seedlings were grown incontrolled environment chambers in pots of fine sand. Plantswere irrigated with either non-saline or saline solutions overa 3-week period. After these treatments, plants were transferredto vessels containing a 5 m M15NO3K (96% atom excess15N) solution,and transpiration as well as concentration of15N and Cl-in roots,stem and leaves were measured after 24 h. Transpiration and15NO3-uptakerates were inhibited after exposure to NaCl and the concentrationof salt pre-treatment determined the intensity of this inhibitoryeffect. To determine the effect of transpiration on NO3-absorption,net15NO3-uptake rate was measured in salt stressed and non-stressedplants exposed to different light intensities or relative humiditiesand also in detached roots. Reduction in NO3-uptake was moreclosely related to Cl-antagonism from salt stress than to reducedtranspiration rate. Copyright 1999 Annals of Botany Company Nitrate, absorption, inhibition transport system, salt, light and humidity.  相似文献   

15.
Scots pine (Pinus sylvestris L.) seedlings were grown for 3years in the ground in open top chambers and exposed to twoconcentrations of atmospheric CO2(ambient or ambient + 400 µmol mol-1) without addition of nutrients and water. Biomassproduction (above-ground and below-ground) and allocation, aswell as canopy structure and tissue nitrogen concentrationsand contents, were examined by destructive harvest after 3 years.Elevated CO2increased total biomass production by 55%, reducedneedle area and needle mass as indicated, respectively, by lowerleaf area ratio and leaf mass ratio. A relatively smaller totalneedle area was produced in relation to fine roots under elevatedCO2. The proportion of dry matter in roots was increased byelevated CO2, as indicated by increased root-to-shoot ratioand root mass ratio. Within the root system, there was a significantshift in the allocation towards fine roots. Root litter constituteda much higher fraction of fine roots in trees grown in the elevatedCO2than in those grown in ambient CO2. Growth at elevated CO2causeda significant decline in nitrogen concentration only in theneedles, while nitrogen content significantly increased in branchesand fine roots (with diameter less than 1 mm). There were nochanges in crown structure (branch number and needle area distribution).Based upon measurements of growth made throughout the 3 years,the greatest increase in biomass under elevated CO2took placemainly at the beginning of the experiment, when trees grownin elevated CO2had higher relative growth rates than those grownunder ambient CO2; these differences disappeared with time.Symptoms of acclimation of trees to growth in the elevated CO2treatmentwere observed and are discussed. Copyright 2000 Annals of BotanyCompany Elevated CO2, Pinus sylvestris, biomass production, allocation, fine roots, root litter, crown structure, nitrogen, C/N ratio  相似文献   

16.
The primary leaves of kidney bean (Phaseolus vulgaris L.) openunder light and close in the dark by the deformation of thepulvinus resulting from diurnal distribution changes of K+,Cl, organic acid (or H+) and NO3. When Rb+ was added as a tracer of K+ to the seedlings throughtheir roots, it was transported to the pulvinus cells duringthe light period but not during the dark period. Transpirationoccurred vigorously in the light but almost stopped in the dark.We concluded that Rb+ absorbed by the roots was carried to thepulvinus by the transpiration stream. Phaseolus vulgaris L., pulvinus, Rb+, diurnal transport transpiration stream  相似文献   

17.
开垦对克氏针茅草地生态系统碳通量的影响   总被引:6,自引:0,他引:6       下载免费PDF全文
 植被–大气间CO2净交换及其对环境变化的响应是目前全球变化研究的热点问题。该研究通过同化箱式法, 在内蒙古农牧交错带对比研究生长季草地生态系统和耕种多年的小麦田生态系统碳通量的变化, 以探讨该地区碳通量的变化规律及影响碳通量主要因子, 并揭示农田开垦对草原碳通量的影响。结果显示: 两个生态系统的群落净气体交换(Net ecosystem exchange, NEE)有明显的季节变化。整个测定期间, 草地生态系统的净气体交换NEE的最高值为–11.26 µmol CO2&#8226;m–2&#8226;s–1, 平均群落净气体交换为–5.33 µmol CO2&#8226;m–2&#8226;s–1; 小麦田群落NEE最大值为–12.29 µmol CO2&#8226;m–2&#8226;s–1, 平均群落净气体交换为–7.66 µmol CO2&#8226;m–2&#8226;s–1。分析发现, 叶面积指数LAI是影响该地区生态系统NEE的主要因子, 相对贫瘠的土壤也是限制该地区生态系统碳固定的一个重要因子。因小麦的生长特性, 在生长中后期, 小麦田生态系统NEE随LAI的变化没有草地生态系统的敏感。此外, 较低的土壤含水量限制了小麦田群落呼吸, 使得小麦田群落呼吸对温度的敏感性降低。  相似文献   

18.
Well-nodulated soya bean (Glycine max L.) plants were allowedto assimilate 13CO2 for 10 h in the light, under steady-stateconditions in which CO2 concentration and 13C abundance wereboth strictly controlled at constant levels. The respiratoryevolution of 13CO2 from roots and nodules and 13C incorporationinto various metabolic fractions were measured during the 13CO2feeding and subsequent 48 h chase period. CO2 respired from nodules was much more rapidly labelled with13C than that from roots. The level of labelling (percentageof carbon currently assimilated during the 13COM2 feeding period)of CO2 respired from nodules reached a maximum of about 87 percent after 4 h of steady-state l3CO2 assimilation and thereafterremained fairly constant. The absolute amount of labelled carbonevolved by the respiration of the nodules during the 10 h 13CO2feeding period was 1·5-fold that of root respiration.These results demonstrated that the currently assimilated (labelled)carbon was preferentially used to support nodule respiration,while root respiration relied considerably on earlier (non-labelled)carbon reserved in the roots. Sucrose pools were mostly composed of currently assimilatedcarbon in all tissues of the plants, since the levels of labellingaccounted for 86–91 per cent at the end of the 13CO2 feeding.In the nodules, the kinetics and levels of sucrose labellingwere in fairly good agreement with those of respired CO2, whilein the roots, the level of labelling of respired CO2 was significantlylower than that of sucrose. Succinate and malate were highly labelled in both roots andnodules but they were labelled much more slowly than sucroseand respired CO2. The kinetics and levels of labelling of theseKrebs cycle intermediates resembled those of major amino acidswhich are derived directly from Krebs cycle intermediates. Itis suggested that large fractions of organic acids in noduleswere physically separate from the respiration site. Glycine max L., Soya bean, 13CO2 assimilation, respiratory evolution of 13CO2, carbon metabolism in root nodules  相似文献   

19.
The effects of increased atmospheric carbon dioxide (CO2) of700 µmol mol–1 and increased air temperature of+ 4C were examined in Lolium perenne L. cv. Vigor, growingin semi-controlled greenhouses. Leaf growth, segmental elongationrates (SER), water relations, cell wall (tensiometric) extensibility(%P) and epidermal cell lengths (ECL) were measured in expandingleaves in spring and summer. In elevated CO2, shoot dry weight (SDW) increased in mid-summer.In both seasons, SDW decreased in elevated air temperatureswith this reduction being greater in summer as compared to spring.Specific leaf area (SLA) decreased in elevated CO2 and in CO2 temperature in both seasons. In spring, increased leaf extensionand SER in elevated CO2 were linked with increased ECL, %P andfinal leaf size whilst in summer all were reduced. In high temperature,leaf extension, SER, %P and final leaf size were reduced inboth seasons. In elevated CO2 temperature, leaf extension,SER, %P, and ECL increased in spring, but final leaf size remainedunaltered, whilst in summer all decreased. Mid-morning waterpotential did not differ with CO2 or temperature treatments.Leaf turgor pressure increased in elevated CO2 in spring andremained similar to the control in summer whilst solute potentialdecreased in spring and increased in summer. Contrasting seasonalgrowth responses of L. perenne in response to elevated CO2 andtemperature suggests pasture management may change in the future.The grazing season may be prolonged, but whole season productivitymay become more variable than today. Key words: Lolium perenne, ryegrass, CO2 and temperature, leaf extension, cell wall rheology  相似文献   

20.
CO2 uptake and diffusion conductance of Valencia orange fruits(Citrus sinensis L. Osbeck) were measured in the field duringthe growing season of 1977/78 to ascertain if, as in the leaf,stomata control photosynthesis and transpiration under changingenvironmental conditions. Measurements were made on 15 yearold trees grown in a sandy loam soil and receiving either adry or a wet treatment. Fruit diffusive conductance was measuredwith a modified water vapour diffusion conductance meter andgross photosynthesis was measured with a 14CO2 uptake meter.Photosynthetically active radiation (PAR) was measured witha quantum sensor. Fruits exposed to light assimilated CO2 ata rate which was 25–50% of that assimilated by leaves.The uptake was dependent on fruit size, PAR, chlorophyll content,and on diffusive conductance of the fruit epidermis. Epidermalconductance showed a diurnal trend which was similar in shapeto that of the leaf except in the late afternoon. Cuticularconductance of the fruit was calculated and ranged between 0.22and 0.30 mm s–1. It was speculated that the CO2 uptakeby the fruit could support the growth of flavedo cell layerswhen exposed to light. Dry soil caused an increase in the 14CO2uptake by fruit possibly caused by the increased potential areaof the stomatal opening per unit of fruit surface area.  相似文献   

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