共查询到20条相似文献,搜索用时 46 毫秒
1.
Liao M. T. Hedley M. J. Woolley D. J. Brooks R. R Nichols M. A. 《Plant and Soil》2000,223(1-2):245-254
The effect of rooting media Cu concentration (0.05–20 mg Cu L-1) on amino acid concentrations and copper speciation in the xylem sap of chicory and tomato plants was measured using 6 week
old plants grown in a nutrient film technique system (NFT). Irrespective of the Cu concentration in the nutrient solutions,
more than 99.68% and 99.74% of total Cu in tomato and chicory xylem sap was in a bound form. When exposed to high Cu concentrations
in the rooting media, amino acid concentrations in the sap increased. Relative to other amino acids, the concentrations of
glutamine (Gln), histidine (His), asparagine (Asn), valine (Val), nicotianamine (NA) and proline (Pro) in tomato xylem saps,
and His, γ-aminobutyric acid (Gaba), glutamic acid (Glu), leucine (Leu), NA and phenylalanine (Phe) in chicory xylem saps
showed the greatest increases. The data indicate that induced synthesis of some free amino acids as a specific and proportional
response to Cu treatment. For a single complexation amino acid, the solution Cu2+concentration vs pH titration curve for NA at 0.06–0.07 mM was most similar, closely followed by His at 0.5–0.6 mM, to the solution Cu2+concentration behaviour in both tomato and chicory xylem sap. It is concluded that increased Cu concentrations in the rooting
media induced selective synthesis of certain amino acid which include NA, His, Asn and Gln which have high stability constants
with Cu. NA and His have the highest binding constants for Cu and the concentrations of NA and His in chicory and tomato xylem
saps can account for all the bound Cu carried in the sap.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
The influence of the endogenous micronutrient chelator, nicotianamine(NA), and of Cu nutrition on the distribution of Cu, Fe, Mn,Zn, and NA was investigated in eight different shoot organs,roots, and in xylem exudates of the NA-containing tomato wildtype Lycopersicon esculentum Mill. cv. Bonner Beste and itsNA-less mutant chloronerva. Contrary to the other heavy metals, copper transport in thexylem was inefficient in the mutant and was enhanced by an applicationof NA to the roots or leaves in proportion to the applied NAconcentration. Also, with NA application, the Cu concentrationin mutant roots decreased significantly, and increased in theshoot. Fe and Mn transport in the xylem was greater in the mutantthan in the wild type, and was decreased in the mutant by theapplication of NA to the leaves. Zn transport in the xylem wasthe same in both genotypes and was unaffected by NA application.After application of NA to leaves and roots of the mutant itwas possible to detect NA in the xylem exudate (up to 2nmolNA(g1 root FWh1). High Cu supply (3 µM) resulted in higher Cu and Mn concentrationsin all organs of the wild type as compared to mutant organs,but Fe concentrations were not influenced. Under high Cu supply(3µM) the NA concentrations of roots and the three youngestleaves of the wild type were higher than under normal Cu supply(0.3 µM). The highest concentrations were found in theshoot apex under both Cu conditions (up to 361 nmol NAg1FW). It is concluded from our experiments and from the high stabilityconstant of the NA-Cu-complex (log K= 18.6) that NA is involvedin Cu translocation whereas for the translocation of Fe, Mn,and Zn, NA is not essential. Key words: Copper transport, micronutrients, mobilization, nicotianamine, xylem 相似文献
3.
The Composition of Phloem Exudate and Xylem Sap from Tree Tobacco (Nicotiana glauca Grah.) 总被引:3,自引:0,他引:3
The composition of xylem sap and exudate from stem incisionsof Nicotiana glauca Grah. was compared in detail. Exudationfrom stem incisions occurred over a 5 min period in certainplants, enabling collection of 530 µl of sap. Therate of exudation showed an exponential decline. Exudate hada high dry matter content (170196 mg ml1) andhigh sugar (sucrose) levels. Xylem sap had a low pH (5.8) andexudate a pH of 7.9. Glutamine dominated the amino compoundsin xylem sap and exudate, and K+ was the major cation. Totalamino compounds in stem exudate reached 10.8 mg ml1 whereasxylem sap contained much lower levels (0.28 mg ml1).All mineral elements and amino compounds with the exceptionof calcium were more concentrated in stem exudate than in xylemsap. Sucrose was labelled heavily in stem exudate following pulsingof an adjacent leaf with 14CO2. A concentration gradient ofsugar (2.1 bar m1) was recorded for stems. Levels ofsucrose, amino compounds and K+ ions in stem exudate showeda diurnal periodicity. Each commodity reached maximum concentrationat or near noon and minimum concentration about dawn. The evidencesuggests that exudate from stem incisions of N. glauca is arepresentative sample of solutes translocated in the phloem. Nicotiana glauca Grah., phloem sap, xylem sap, sucrose, amino compounds, mineral ions 相似文献
4.
Xylem Transport and Storage of Amino Acids by S.W. Australian Mistletoes and their Hosts 总被引:3,自引:0,他引:3
Amino acid composition of xylem (tracheal) sap and ethanolicextracts of shoots of mistletoes (Amyema spp. and Lysiana casuarinae)and their hosts were compared, using material collected in theirnative habitats. Data indicated that certain host xylem soluteswere transferred directly to the parasite xylem, while otherswere either not absorbed or were metabolized prior to transfer.Certain solutes were major constituents of parasite xylem, butundetected or only in trace amount in the host. Shoot aminoacid pools of parasites differed markedly from those of hosts.The mistletoe, Amyema preissii, exhibited differential storageand transport of arginine when parasitizing three differentspecies, but accumulated proline on only two of these hosts.Host- specific amino acids (djenkolic acid in Acacia saligna,and tyramine in Acacia acuminata) were transported and accumulatedin relatively large amounts by the parasite, but were not detectedin other associations. Proline was the major solute of Amyemalinophyllum parasitizing Casuarina obesa, but arginine predominatedin Lysiana casuarinae on the same host. However, when L. csuarinaeparasitized A. linophyllum, in turn parasitic on C. obesa, theLysiana accumulated equal amounts of proline and arginine andmore asparagine than when directly on the Casuarina. Xylem feedingof 15N-labelled aspartic acid or 13N-(amide labelled) asparagineto cut shoots or whole haustoria-bearing plants of the mistletoeA. preissii resulted in 6873% of the 15N of aspartateand 2430% of that of asparagine appearing in ethanol-solubleshoot amino compounds other than the fed solute. 15N labellingpatterns of detached shoots were not noticeably different fromthat of whole plants suggesting that the haustorium had relativelylittle effect on processing incoming solutes. Alanine, glutamine,and arginine were principal recipients of 15N from aspartate,alanine and glutamine in the case of fed asparagine. It is estimatedthat 24% of the carbon requirements for dry matter accumulationin Amyema linophyllm were met by intake of xylem sap solutesfrom its host Casuarina obesa. Key words: Amino acids, xylem transport, mistletoes, host: parasite relations, N metabolism 相似文献
5.
Wheat Phloem sap was collected without contamination from thestylets of small brown planthopper severed by a YAG laser beam.The sugar, amino acid and inorganic ion composition was determinedusing only one µl of the sap. The sap had a high sucrose level (251 mM), and also a high K+level (299 mM). Total amino acid compounds in the sap reached262 mM. The dominant amino acids were glutamic acid, asparticacid and serine, while r-amino butylic acid was absent. Themajor anion in the sap was Cl and its concentration was25.1 mM. Nitrate was also present at a concentration of 8.1mM. These results suggested that the sap obtained from the cut endof the stylets of the small brown planthopper was a phloem originof wheat. (Received May 21, 1986; Accepted August 7, 1986) 相似文献
6.
Mulholland B.J.; Taylor I.B.; Black C.R.; Roberts J.A. 《Journal of experimental botany》1996,47(4):551-556
The abscisic acid (ABA)-deficient mutant of barley, Az34, exhibiteda much reduced rate of leaf expansion at a bulk density of 1.6g cm3 as compared to the isogenic wild-type variety,Steptoe. Az34 had a consistently lower xylem sap ABA concentrationat 7 d and 14 d after emergence (DAE). The xylem sap data suggestthat ABA present at Steptoe concentrations may have a directrole in maintaining leaf expansion at the sub-critical bulkdensity (1.6 g cm3 To test this hypothesis, additionof synthetic ABA either to the rooting environment (100 nM)or directly to the xylem sap (5 pg µl1 to reproducethe xylem sap ABA concentrations found in Steptoe, increasedleaf expansion in Az34 to the wild-type level. Furthermore,feeding Steptoe xylem sap to Az34 produced similar effects.These experiments provide direct evidence of a positive rolefor ABA as a root-to-shoot signal which assists in maintainingleaf growth in plants experiencing subcritical levels of compactionstress. Key words: ABA-deficient mutant, leaf expansion, xylem sap, ABA 相似文献
7.
Solute composition of root xylem sap of common native hostsof quandong (Santalum acuminatum) was compared with that ofcorresponding xylem sap and ethanolic extracts of endophytictissues of haustoria of the hemiparasite. Each host transporteda characteristic set of organic nitrogenous solutes, but littleor no nitrate, and the data indicated only limited direct flowof amino compounds between xylem streams of hosts and parasite.Proline predominated in the haustorium and xylem ofSantalum,but was at negligible levels in the xylem of most hosts. Sucrose,fructose, glucose, malate and citrate were at high levels inall saps, and fructose especially prominent inSantalum. Chloride,sulphate and phosphate were the principal inorganic anions ofthe xylem. Based on C:N ratios of xylem and dry matter ofSantalumandassuming a 70% or more dependence on the host for N, it wasestimated thatSantalumwould gain approximately one third ofits C requirement for dry matter production heterotrophicallyfrom the xylem of its hosts. Infiltration of xylem of haustoria-bearingroot segments of a major host (Acacia rostellifera) with a rangeof15N labelled substrates resulted in 4080% of the15Nof endophytes of the attached haustoria being received as proline.Nitrate reductase activity was induced in haustoria followinghost xylem feeding of nitrate. The study concludes that haustoriaofSantalumact as a major site of synthesis and export of prolineand might therefore play an important role in osmotic adjustmentof the parasite and its related acquisition of water from hosts. Root hemiparasite; Santalum acuminatum; 15N labelled substrates; xylem transport; proline; osmoregulation 相似文献
8.
AGARWALA S. C.; CHATTERJEE C.; SHARMA C. P.; NAUTIYAL N. 《Journal of experimental botany》1985,36(6):881-888
Sugarbeet (Beta vulgaris L.) plants were grown in refined sandat graded levels of copper ranging from acute deficiency (0.000325µg Cu cm3) to excess (65 µg Cu cm3).Visible effects of copper deficiency appeared up to 0-00065µg Cu cm3and depression in growth up to 00065µCucm3. Copper deficiency decreased the concentrations ofDNA and RNA and the activities of polyphenol oxidase, cytochrome-coxidase, catalase and aldolase; and it increased the activitiesof peroxidase, ribonuclease and acid phosphatase in leaves.The maximum sucrose concentration in roots was obtained at 0-65µCucm3 Twenty four h after infiltration of a solution of 65µCucm3into copper deficient leaves, the activities of cytochrome-coxidase and peroxidase had increased even in the presence ofcycloheximide but that of polyphenol oxidase increased onlyin the absence of this inhibitor. Key words: Beta vulgaris, Cu deficiency: Enzymes 相似文献
9.
The present study investigates whether previously acquired boron(B) in mature leaves in white lupin can be retranslocated intothe rapidly growing young reproductive organs, in response toshort-term (3 d) interrupted B supply. In a preliminary experimentwith white lupin in soil culture, B concentrations in phloemexudates remained at 300–500 µM, which were substantiallyhigher than those in the xylem sap (10–30 µM). Thehigh ratios of B concentrations in phloem exudates to thosein the xylem sap were close to values published for potassiumin lupin plants. To differentiate old B in theshoot from new B in the root, an experiment wascarried out in which the plants were first supplied with 20µM 11B (99.34% by weight) in nutrient solution for 48d after germination (DAG) until early flowering and then transferredinto either 0.2 µM or 20 µM 10B (99.47% by weight)for 3 d. Regardless of the 10B treatments, significant levelsof 11B were found in the phloem exudates (200–300 µMin 20 µM 10B and 430 µM in 0.2 µM 10B treatment)and xylem sap over the three days even without 11B supply tothe root. In response to the 0.2 µM 10B treatment, thetranslocation of previously acquired 11B in the young (the uppermostthree leaves), matured, and old leaves was enhanced, coincidingwith the rise of 11B in the xylem sap (to >15 µM) andphloem exudates (430 µM). The evidence supports the hypothesisthat previously acquired B in the shoot was recirculated tothe root via the phloem, transferred into the xylem in the root,and transported in the xylem to the shoot. In addition, somepreviously acquired 11B in the leaves may have been translocatedinto the rapidly growing inflorescence. Phloem B transport resultedin the continued net increment of 11B in the flowers over 3d without 11B supply. However, it is still uncertain whetherthe amount of B available for recirculation is adequate to supportreproductive growth until seed maturation. Key words: 10B, 11B, B recirculation, Lupinus albus L., phloem exudate, xylem sap
Received 9 October 2007; Revised 28 November 2007 Accepted 30 November 2007 相似文献
10.
Chemical Composition of Bleeding Xylem Sap from Kiwifruit Vines 总被引:5,自引:0,他引:5
A study of the chemical composition and charge balance was madeof bleeding xylem sap collected from excised one-year-old extensionshoots of healthy, Mn-deficient, Mn-toxic and Zn-deficient kiwifruitvines (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson)immediately prior to leafburst. The exudates were analysed formacronutrient cations and anions, trace elements, amino acids,organic acids and sugars. Major charged species measured wereCa (13.3 mM), K (8.9 mM), Mg (5.6 mM), malate (12.5 mM) andphosphate (5.8 mM). Glutamine (12 mM) was the predominant Ncarrier identified, accounting for 58 per cent of the totalN followed by NO2-N (4.5 per cent), NH4+-N (3.5 per cent)and arginine-N (2.9 per cent). Approximately 22 per cent ofthe N was in a hydrolysable proteinaceous fraction comprisingmainly glutamine and glutamate. Eighteen free proteinaceousamino acids were idetified in sap, the most abundant being glutamine,glutamic acid, valine, isoleucine and phenylalanine. Computersimulation of the chemical composition predicted that in additionto hydrated cations, ion pairs formed between inorganic components(SO42, HPO42, H2PO4) and cations (Ca2+,Mg2+, Mn2+), plus metal-organic ligand complexes (Ca Malate,Zn Malate, FeCit, CuHis, CuGln) are important species involvedin translocation. The solubility product of hydroxyapatite wasexceeded in all exudates although in vitro precipitation wasnot observed. To achieve electroneutrality with the componentsmeasured, however, formation of precipitate precursors (hydroxyapatitenuclei) had to be assumed. Irregularities in Mn nutrition (butnot Zn) were clearly indicated by the elemental compositionof exudate suggesting the use of sap analysis as a possiblepre-season indicator of nutritional status for this species. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson, kiwifruit, xylem sap composition, trace metals, amino acids, organic acids 相似文献
11.
Characterization of Cd translocation and identification of the Cd form in xylem sap of the Cd-hyperaccumulator Arabidopsis halleri 总被引:1,自引:0,他引:1
Arabidopsis halleri is a Cd hyperaccumulator; however, the mechanismsinvolved in the root to shoot translocation of Cd are not wellunderstood. In this study, we characterized Cd transfer fromthe root medium to xylem in this species. Arabidopsis halleriaccumulated 1,500 mg kg–1 Cd in the shoot without growthinhibition. A time-course experiment showed that the releaseof Cd into the xylem was very rapid; by 2 h exposure to Cd,Cd concentration in the xylem sap was 5-fold higher than thatin the external solution. The concentration of Cd in the xylemsap increased linearly with increasing Cd concentration in theexternal solution. Cd transfer to the xylem was completely inhibitedby the metabolic inhibitor carbonyl cyanide 3-chlorophenylhydrazone(CCCP). Cd concentration in the xylem sap was decreased by increasingthe concentration of external Zn, but enhanced by Fe deficiencytreatment. Analysis with 113Cd-nuclear magnetic resonance (NMR)showed that the chemical shift of 113Cd in the xylem sap wasthe same as that of Cd(NO3)2. Metal speciation with Geochem-PCalso showed that Cd occurred mainly in the free ionic form inthe xylem sap. These results suggest that Cd transfer from theroot medium to the xylem in A. halleri is an energy-dependentprocess that is partly shared with Zn and/or Fe transport. Furthermore,Cd is translocated from roots to shoots in inorganic forms. 相似文献
12.
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: 10151023. 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 m3 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
13.
CO2 efflux, CO2 concentration and photosynthetic refixation in stems of Eucalyptus globulus (Labill.)
下载免费PDF全文
![点击此处可从《Journal of experimental botany》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cerasoli S.; McGuire M. A.; Faria J.; Mourato M.; Schmidt M.; Pereira J. S.; Chaves M. M.; Teskey R. O. 《Journal of experimental botany》2009,60(1):99-105
In spite of the importance of respiration in forest carbon budgets,the mechanisms by which physiological factors control stem respirationare unclear. An experiment was set up in a Eucalyptus globulusplantation in central Portugal with monoculture stands of 5-year-oldand 10-year-old trees. CO2 efflux from stems under shaded andunshaded conditions, as well as the concentration of CO2 dissolvedin sap [CO2*], stem temperature, and sap flow were measuredwith the objective of improving our understanding of the factorscontrolling CO2 release from stems of E. globulus. CO2 effluxwas consistently higher in 5-year-old, compared with 10-year-old,stems, averaging 3.4 versus 1.3 µmol m–2 s–1,respectively. Temperature and [CO2*] both had important, andsimilar, influences on the rate of CO2 efflux from the stems,but neither explained the difference in the magnitude of CO2efflux between trees of different age and size. No relationshipwas found between efflux and sap flow, and efflux was independentof tree volume, suggesting the presence of substantial barriersto the diffusion of CO2 from the xylem to the atmosphere inthis species. The rate of corticular photosynthesis was thesame in trees of both ages and only reduced CO2 efflux by 7%,probably due to the low irradiance at the stem surface belowthe canopy. The younger trees were growing at a much fasterrate than the older trees. The difference between CO2 effluxfrom the younger and older stems appears to have resulted froma difference in growth respiration rather than a differencein the rate of diffusion of xylem-transported CO2. Key words: Eucalyptus globulus, refixation, stem respiration
Received 19 May 2008; Revised 14 September 2008 Accepted 8 October 2008 相似文献
14.
Nodulated 1-1.5-year-old plants of Acacia littorea grown inminus nitrogen culture were each partnered with a single seedlingof the root hemiparasite Olax phyllanthi. Partitioning of fixedN between plant organs of the host and parasite was studiedfor the period 48 months after introducing the parasite.N fluxes through nodules of Acacia and xylem-tapping haustoriaof Olax were compared using measured xylem flows of fixed Nand anatomical information for the two organs. N2 fixation duringthe study interval (635 µg N g FW nodules1 d1)corresponded to a xylem loading flux of 0.20 µg N mm2d1 across the secretory membranes of the pencycle parenchymaof the nodule vascular strands. A much higher flux of N (4891µg mm2 d1) exited through xylem at the junctionof nodule and root. The corresponding flux of N from host xylemacross absorptive membranes of the endophyte parenchyma of Olaxhaustorium was 1.15 µg N mm1 d1, six timesthe loading flux in nodules. The exit flux from haustorium toparasite rootlet was 20.0 pg N mm1 d1, 200-foldless than that passing through xylem elements of the nodule.Fluxes of individual amino compounds in xylem of nodule andhaustorium were assessed on a molar and N basis. N flux valuesare related to data for transpiration and partitioning of Cand N of the association recorded in a companion paper. Key words: Olax phyllanthi, host-parasite relationships, N flux, Acacia, N2 fixation 相似文献
15.
The amino acid compositions of the root xylem saps of Olax phyllanthi and a range of its common hosts were examined in native coastal heath in Western Australia and in pot cultures of Olax reliant on single hosts. When hosts specializing in the xylem transport of one major solute (asparagine, glutamine, histidine, arginine or proline) were exploited, the endophytic tissue of haustoria and the xylem sap of Olax showed much lower proportions of this than of other solutes, suggesting pronounced metabolic transformation prior to xylem loading by the parasite. However, the xylem sap of Olax did partly reflect the compositions of its hosts; for example, djenkolic acid and pipecolic acid were present when Olax was parasitic on species of Acacia, and levels of citrulline and aspartic acid were higher than normal when it exploited hosts transporting large amounts of these compounds. Back-flow of S-ethenyl cysteine, a novel amino acid specific to Olax, was observed to another root hemiparasite (Exocarpos sparteus) in native habitat and to certain non-parasitic hosts in water-stressed pot cultures. Haustoria exhibited high levels of glutamine synthetase but showed appreciable in vivo nitrate reductase activity only when on hosts with high xylem levels of nitrate. 相似文献
16.
Nitrogen Assimilation in Barley (Hordeum vulgare L. cv. Mazurka) in Response to Nitrate and Ammonium Nutrition 总被引:6,自引:0,他引:6
Barley plants (Hordeum vulgare L. cv. Mazurka) were grown inaerated solution cultures with 2 mM or 8 mM inorganic nitrogensupplied as nitrate alone, ammonium alone or 1:1 nitrate+ammonium.Activities of the principal inorganic nitrogen assimilatoryenzymes and nitrogen transport were measured. Activities ofnitrate and nitrite reductases, glutamine synthetase and glutamatesynthase were greater in leaves than in roots but glutamatedehydrogenase was most active in roots. Only nitrate and nitritereductases changed notably (410 times) in response tothe different nitrogen treatments. Nitrate reductase appearedto be rate-limiting for nitrate assimilation to glutamate inroots and also in leaves, where its total in vitro activitywas closely related to nitrate flux in the xylem sap and wasslightly in excess of that needed to reduce the transportednitrate. Xylem nitrate concentration was 13 times greater thanthat in the nutrient solution. Ammonium nitrogen was assimilatedalmost completely in the roots and the small amount releasedinto the xylem sap was similar for the nitrate and the ammoniumtreatments. The presence of ammonium in the nutrient decreasedboth export of nitrate to the xylem and its accumulation inleaves and roots. Nitrate was stored in stem bases and was releasedto the xylem and thence to the leaves during nitrogen starvation.In these experiments, ammonium was assimilated principally inthe roots and nitrate in the leaves. Any advantage of this divisionof function may depend partly on total conversion of inorganicnitrogen to amino acids when nitrate and ammonium are givenin optimal concentrations. Hordeum vulgare L., barley, nitrate, ammonium, nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, glutamate dehydrogenase, nitrogen transport 相似文献
17.
Concentrations and Transport of Solutes in Xylem and Phloem along the Leaf Axis of NaCl-treated Hordeum vulgare 总被引:5,自引:0,他引:5
WOLF OLAF; MUNNS RANA; TONNET M. LORRAINE; JESCHKE W. DIETER 《Journal of experimental botany》1990,41(9):1133-1141
Hordeum vulgare cv. California Mariout was established in sandculture at two different NaCl concentrations (0.5 mol m3control and 100 mol m3) in the presenceof 6.5 mol m3 K +. Between 16 and 31 d after germination,before stem elongation started, xylem sap was collected by useof a pressure chamber. Collections were made at three differentsites on leaves 1 and 3: at the base of the sheath, at the baseof the blade, i.e. above the ligule, and at the tip of the blade.Phloem sap was collected from leaf 3 at similar sites throughaphid stylets. The concentrations of K +, Na+, Mg2+ and Ca2+were measured. Ion concentrations in xylem sap collected at the base of leaves1 and 3 were identical, indicating there was no preferentialdelivery of specific ions to older leaves. All ion concentrationsin the xylem decreased from the base of the leaf towards thetip; these gradients were remarkably steep for young leaves,indicating high rates of ion uptake from the xylem. The gradientsdecreased with leaf age, but did not disappear completely. In phloem sap, concentrations of K+ and total osmolality declinedslightly from the tip to the base of leaves of both controland salt-treated plants. By contrast, Na+ concentrations inphloem sap collected from salt-treated plants decreased drasticallyfrom 21 mol m3 at the tip to 7.5 mol m3 at thebase. Data of K/Na ratios in xylem and phloem sap were used to constructan empirical model of Na+ and K+ flows within xylem and phloemduring the life cycle of a leaf, indicating recirculation ofNa+ within the leaf. Key words: Hordeum vulgare, xylem transport, phloem transport, NaCl-stress 相似文献
18.
Tiziana Centofanti Zehra Sayers Maria Isabel Cabello-Conejo Petra Kidd Naoko K. Nishizawa Yusuke Kakei Allen P. Davis Richard C. Sicher Rufus L. Chaney 《Plant and Soil》2013,373(1-2):59-75
Aims
An improved understanding of the Ni root-to-shoot translocation mechanism in hyperaccumulators is necessary to increase Ni uptake efficiency for phytoextraction technologies. It has been presumed that an important aspect of Ni translocation and storage involves chelation with organic ligands. It has been reported that exposing several Ni hyperaccumulator species of Alyssum to Ni elicited a large increase in the histidine level of the xylem sap. In later studies it was shown that as time progressed the histidine:Ni ratio dropped considerably. Moreover, previous studies analyzed the relationship between Ni and ligands in plants that were exposed to Ni only for a few hours and therefore obtained results that are unlikely to represent field soils where plants are at steady-state Ni uptake. The aim of this study was to understand the quantitative relationship between Ni and organic ligands in the xylem sap of various Alyssum genotypes or species that reached steady-state Ni uptake after being exposed to Ni in either nutrient solution or serpentine soil for up to 6 weeks.Methods
Total Ni concentration, 17 amino acids, 9 organic acids, and nicotianamine were measured in xylem sap of 100-day old plants of Alyssum.Results
Results showed that the concentration of Ni in xylem sap of various Alyssum genotypes was 10–100 fold higher than the concentration of histidine, malate, citrate, and nicotianamine, which were the predominant Ni ligands measured in the sap.Conclusion
When the physiology of the whole plant is taken into account, our results indicate that the concentration of organic chelators is too low to account for the complexation of all the Ni present in the xylem sap of Alyssum at steady-state Ni hyperaccumulation, and suggest that most of the Ni in xylem sap of this species is present as the hydrated cation. 相似文献19.
GROENEVELD HENRI W.; ELINGS JOPIE C.; BLANCO MAGDALENA SOFIA JORGE; BRAMWELL DAVID 《Annals of botany》1988,62(3):303-311
Seedlings from Euphorbia canariensis and Euphorbia lambii weregrown in the dark at 25 °C. Protein and triglyceride contentas well as levels of sugars and amino acids in the endospermwere determined during endosperm depletion. In the endospermof Euphorbia canariensis, relatively low levels of amino acids(up to 1 µmol.endosperm1) were found of which glutamine/glutamateaccounted for 40% at the stage of radicle emergence. High levelsof amino acids (up to 4 µmol.endosperm1) comparedwith sugars (up to 2 µmol sucrose.endosperm1) weredetected in the endosperm of Euphorbia lambii. Arginine wasthe main component (28 µmol%) of the amino acids in thistissue. In both species amino acid composition changed graduallyduring endosperm depletion. Cotyledons retained their ability to absorb a variety of watersoluble substrates after removal of the endosperm. 14C from[U-14C]sucrose was effectively incorporated into the triterpenesof the laticifers and to a lesser extent into the sterols ofthe seedling. The highest incorporation values were found inyoung seedlings about 2 d after the emergence of the radicle.Seedlings of this age also showed high incorporation rates of14C from labelled alanine, serine, threonine, valine, leucineand isoleucine into both triterpenols and sterols, but no generalconclusions about metabolic channelling in lipid synthesis couldbe made. Endosperm, Euphorbia canariensis L. Euphorbia lambii Svent., sterols, triterpenols, amino acids, laticifer, biosynthesis 相似文献
20.
Barthes Laure; Delens Eliane; Bousser Agns; Hoarau Jackson; Prioul Jean-Louis 《Journal of experimental botany》1996,47(4):485-495
The xylem exudation of detopped 7-d-old seedlings of Zea maysL. doubled when KCI was present in the root medium comparedto seedlings maintained on water. It was further enhanced whenKCI was replaced by nitrogen compounds such as nitrate, ammoniumand glutamine. The role of the nitrate assimilation pathwayon the enhancement of xylem exudation rate was investigatedusing tungstate, an inhibitor of nitrate reductase (NR) activity,and phosphinothricin or methionine sulphoximine, inhibitorsof glutamine synthetase (GS) activity. The sap levels of NO3,NH4+, glutamine, and asparagine was used to ascertain the invivo inhibition of both enzymes. The tungstate effects werealso checked by measuring leaf in vitro NA activity and NR proteincontent. Xylem exudation rate of detopped seedlings fed withKNO3 decreased when the nitrate assimilation pathway was blockedeither at the NR or at GS sites. This decrease was preventedwhen urea (acting as NH4+ supply) was given simultaneously withtungstate. KNO3 does not act directly on exudation, but throughthe involvement of NH4+. The involvement of glutamine was alsoshown since GS inhibition resulted in a cancellation of theenhancing effect of KNO3 on exudation. As change of exudationrate was not linked to change in sap osmolarity, it is assumedthat the assimilation chain could modify root water conductance.The role of glutamine was discussed. Key words: Exudation, maize, nitrate, conductance, NR, GS 相似文献