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1.
Summary Bleeding from phloem of cut distal tips of attached fruits was demonstrated in the genera Spartium, Genista, Lupinus and Jacksonia. Bleeding occurred over a 2–25 min period enabling 0.5–10 l of sap to be collected from a fruit. A detailed study of Lupinus albus L. showed that exudation rate declined exponentially after cutting, but without any change with time in solute levels in exudate. Bleeding resumed at its initial rate and solute concentration on recutting the fruit tip.Phloem exudates had a high pH (7.8-8.0), a sucrose content of 100–210 mg ml-1 but only traces of monosaccharides. Surrounding pod tissues contained only 15–35 mg ml-1 of sugars (tissue water basis) more than two thirds of this monosaccharide. Amino compounds were present in phloem exudates at 8–28 mg ml-1, asparagine and glutamine predominating but a wide spectrum of other amino acids being also present. No significant differences in levels of organic solutes were observed in phloem exudates collected from tips of attached versus detached fruits, from phloem exudates collected from fruit tips versus pedicels, or from basal versus distal ends of a detached fruit.Potassium was the major cation (1.5–2.2 mg ml-1) of the phloem exudate, Ca2+ was at a much lower level than either Mg2+ or Na+. Trace element levels in phloem exudates appeared to be influenced by availability to the plant from the rooting medium. Nitrate was absent though detectable in non-vascular tissues of the shoot.
14C- labelled assimilates were detected in exudates of L. albus one hour after feeding a source leaf 14CO2; sucrose, organic acids and certain amino compounds achieved high specific labelling. 14CO2 feeding studies coupled with the phloem bleeding technique revealed highly specific source-sink relationships between foliar organs and fruits of the primary inflorescence. 相似文献
2.
The low-molecular-weight (LMW), low-abundance protein composition of lupin
and pea phloem exudates was determined using matrix-assisted laser
desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS)>
Phloem sap was collected from lupin inflorescence stalks and pods (using
shallow incisions) or pea seedlings (by placing cut stems in an EDTA
solution). Western blot analysis of phloem exudate proteins with either a
polyclonal antibody raised against Ricinus communis
sieve-tube exudate proteins or pea Rubisco antibody revealed that the
collected exudates contained phloem sap, and that contamination with other
plant fluids was negligible. Three matrix combinations were tested to
assess their ability to facilitate protein ionization. Sinapinic acid in
combination with trifluoroacetic acid yielded the cleanest mass spectra,
and revealed an array of LMW proteins ranging from 2 to 10 kDa. For pea
phloem exudate, the addition of protease inhibitors to the exudate
collection solution prevented proteolysis of endogenous proteins; the
inhibitors did not interfere with the detection of proteins. The
sensitivity of this technique was sufficient to detect changes in LMW
phloem peptides throughout plant development in lupin, or to detect
differences in the phloem peptide composition of two genotypes of pea.
Because only limited sample preparation is required, MALDI-TOF-MS is a
useful technique for characterizing complex fluids such as phloem
sap. 相似文献
3.
The osmotic characteristics of phloem-sap exudation were examined in soil-grown and watercultured plants of Ricinus communis L. Prolonged exudation occurred from bark incisions in water-cultured plants. Fresh incisions caused large alterations in solute flux, but phloem-sap solute potential s changed by less than ±8% over a period of 7 h. This was associated with a constancy in the levels of sucrose and K+, the principal solutes in the sap. Studies with foliar-applied tracers and leaf-excision experiments suggested that exudation was maintained by solute loading from mature leaves. A wide range of mass transfer values through the phloem was found, these being a function of exudation rate. We consider that the exudation process possesses essentially similar characteristics to phloem transport in the intact plant. The way in which bark incisions bring about large changes in solute flux is discussed in terms of the physical properties of the sieve-tube system.Abbreviations
water potential
- s
solute potential
- p
pressure potential 相似文献
4.
Shelp, B. J. 1987. The composition of phloem exudate and xylemsap from broccoli (Brassica oleracea var. italica) suppliedwith NH+4, NO3 or NH4NO3.J. exp. Bot. 38: 16191636. The detailed composition of xylem sap and exudate from stemincisions of attached inflorescences of broccoli (Brassica oleraceavar. italica) was compared in plants supplied with NH+4, NO3or NH4NO3. A phloem origin for the exudate was suggested fromthe high levels of sugars (71133 mg cm-3), amino acids(8·1-26·7 mg cm3) and K. (2·33·8mg cm3), the low levels of NO3 and Ca, the high C: N (w/w) ratios(8·333), and the alkaline pH (7·27·3).In contrast, the xylem sap was mildly acidic (pH 5·66·0),and possessed lower levels of all organic and inorganic solutesbut NO3 and Ca, and lower ratios of K: Ca, Mg: Ca and C: N (0·64·4). Glutamine was the predominant o-phthalaldehyde-reactive aminocompound in both transport fluids with the next most abundantamino acids dependent on sap type and N-form. Together witharginine, -aminobutyric acid, which was found only in the xylemstream, was enhanced by NH+4compared to NO3 -nutrition suggestingthat glutamate metabolism was stimulated in the roots. Underlimiting N the amino acid concentrations in the transport fluidswere greater with NH+4 than with NO3. NO3 reduction occurredin both the root and shoot with the latter site predominatingover the entire N range (0-300 mol m3). Even though the compositionof nitrogenous solutes in the xylem was dependent on cultivarand N source, the composition of the phloem streams supplyingthe developing inflorescence was relatively unaffected. The data on the element composition of organs and phloem sapare interpreted to suggest that, in spite of the restrictedmobility of some elements such as B and Mn, a significant proportionof their total supply to developing sinks is carried in thephloem stream. Key words: Transport fluid composition, plant nutrition, phloem mobility. 相似文献
5.
Characterization of the elicitor-induced biosynthesis and secretion of genistein from roots of Lupinus luteus L 总被引:2,自引:0,他引:2
Genistein is a multi-functional isoflavonoid naturally secreted from roots
of hydroponically grown legume plants. Roots of hydroponically cultivated
yellow lupin (Lupinus luteus L.) plants, transferred
into water secreted minor amounts of genistein (about 5 g g-1 fr. wt.). Secretion of
genistein from L. luteus roots (rhizosecretion) was
stimulated dramatically to over 100 g
g-1 root fresh weight by soluble chitosan, salicylic
acid (SA) and potassium cyanide (KCN) supplied at 0.12% (w/v), 800
M and 400 M, respectively. Other identified elicitors
caused a smaller induction of genistein rhizosecretion. Increased levels of
genistein in root exudates corresponded to greater amounts of genistein in
root tissue. Elicitor-induced rhizosecretion of genistein was based on
de novo synthesis and was inhibited by glyphosate and
other less specific metabolic inhibitors. Except for NaF:AICI3, all tested
elicitors of genistein rhizosecretion produced a distinct bell-shaped
dose-response curve. Most of the elicitor-induced rhizosecretion of
genistein occurred during the first day, followed by a gradual decline.
Further addition of elicitor treatments had little effect of genistein
rhizosecretion, indicating that the induction of genistein rhizosecretion
by the identified elicitors is a once only event.Keywords:
Genistein, isoflavonoids, Lupinus luteus,
elicitation, exudation.
相似文献
6.
Wolterbeek, H. Th. and De Bruin, M. 1986. Xylem and phloem importof Na+, K+ , Rb+, Cs+ and in tomato fruits: differential contributions from stem and leaf.J.exp. Bot. 37: 928939. The transport of Na+, K+, Rb+, Cs+ and into developing fruits of tomato (an inbred lineof Lycopersicon esculentum Mill. cv. Tiny Tim) was measured.Element solutions were introduced into the transpiration streamthrough the cut stem bases of plant parts consisting of a stempart with single green fruit, both with and without attachedfully expanded leaf. Measurements were carried out of the accumulationin the fruit of the gamma-ray emitting radiotracers 24Na+, 42K+,86Rb+, 134Cs+ and The transport into the fruit was expressed by a single parameter taking intoaccount volume flows varying with time and experiments. Xylemto phloem transfer in the stem as a source of fruit elementsupply was shown to be inversely related with the velocity offlow of the stem xylem. The results also indicated that thetransfer system in the stem was more rapidly equilibrated thanit was in the leaf. Stem loading of the phloem is suggested as a possible mechanismregulating the solute influx in fruits under varying flow velocitiesof the stem xylem, while fruit influx of phloem solutes, whichwere loaded in the leaf, may play a major role in influx regulationunder conditions of varying solute concentrations. Key words: Alkali ions, tomato fruits, stem and leaf phloem loading 相似文献
7.
Determination of phytohormones in phloem exudate from tree species by radioimmunoassay 总被引:3,自引:0,他引:3
A sensitive and specific radioimmunoassay was used to determine quantitatively four of the most important phytohormones in the phloem exudate from 14 different tree species of 8 genera. For cytokinins and indole-3-acetic acid (IAA) we found higher concentrations than those reported previously for other species. The gibberellin values were of the same order of magnitude as in earlier analyses (with different methods) of tree phloem exudates, but lower than the ones reported for Ricinus. Free abscisic acid (ABA) was found in tree phloem exudates in similar concentrations as before in Yucca or palm phloem exudate, but at considerably lower ones than reported for Ricinus and in Lupinus phloem exudate.Abbreviations IAA
indole-3-acetic acid
- ABA
abscisic acid
- GA
gibberellic acid 相似文献
8.
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
9.
The involvement of Na+, K+,
Cl- or Ca2+ in the regulation
of salinity stress-induced proline accumulation via the inhibition of the
activity of proline dehydrogenase (PDH; EC 1.4.3.1), a catabolic enzyme of
proline, was investigated in the marine green macroalga Ulva
fasciata Delile. After 6 h of exposure to elevated artificial
seawater (ASW) salinity, adjusted either by increasing the NaCl content in
30 ASW (a change in ion ratio) or by concentrating ASW (a
constant ion ratio), the contents of Na+,
K+ and Cl- linearly
accumulated with increasing salinity from 30-90 (parts per
thousand); the accumulation pattern of each ion was similar between the two
treatments. An increase in NaCl content in ASW induced proline
accumulation, but decreased both the PDH activity and the total
water-soluble Ca2+ contents, while concentrated ASW
had no effect. As compared to a constant value at 30, both the
contents of total and water-soluble CA2+ and the
activity of PDH decreased 1 h after exposure to 60 (adjusted by
increasing NaCl content in 30 ASW) and concomitantly the
content of seawater Ca2+ increased, while proline
accumulated after 3 h. The addition of 15 mM ethylene
glycol-bis-(2-aminoethyl ether)
N,N,N-tetraacetic acid (EGTA) in
60 ASW (adjusted by increasing the NaCl content in
30 ASW) enhanced both the proline accumulation and the decrease
in the content of total and water-soluble cellular
Ca2+ and the activity of PDH; the effects of EGTA
were reversed by 10 mM CaSO4. These results indicate that a loss of
cellular Ca2+ is associated with the NaCl induction
of proline accumulation via an inhibition of PDH activity in U.
fasciata. 相似文献
10.
Careful cutting of the hypocotyl of Ricinus communis L. seedlings led to the exudation of pure sieve-tube sap for 2–3 h. This offered the possibility of testing the phloem-loading system qualitatively and quantitatively by incubating the cotyledons with different solutes of various concentrations to determine whether or not these solutes were loaded into the sieve tubes. The concentration which was achieved by loading and the time course could also be documented. This study concentrated on the loading of sucrose because it is the major naturally translocated sieve-tube compound. The sucrose concentration of sieve-tube sap was approx. 300 mM when the cotyledons were buried in the endosperm. When the cotyledons were excised from the endosperm and incubated in buffer, the sucrose concentration decreased gradually to 80–100 mM. This sucrose level was maintained for several hours by starch breakdown. Incubation of the excised cotyledons in sucrose caused the sucrose concentration in the sieve tubes to rise from 80 to 400 mM, depending on the sucrose concentration in the medium. Thus the sucrose concentration in the sieve tubes could be manipulated over a wide range. The transfer of labelled sucrose to the sieve-tube sap took 10 min; full isotope equilibration was finally reached after 2 h. An increase of K+ in the medium or in the sieve tubes did not change the sucrose concentration in the sievetube sap. Similarly the experimentally induced change of sucrose concentration in the sieve tubes did not affect the K+ concentration in the exudate. High concentrations of K+, however, strongly reduced the flow rate of exudation. Similar results were obtained with Na+ (data not shown). The minimum translocation speed in the sieve tubes in vivo was calculated from the growth increment of the seedling to be 1.03 m·h-1, a value, which on average was also obtained for the exudation system with the endosperm attached. This comparison of the in-vivo rate of phloem transport and the exudation rate from cut hypocotyls indicates that sink control of phloem transport in the seedlings of that particular age was small, if there was any at all, and that the results from the experimental exudation system were probably not falsified by removal of the sink tissues.Abbreviations PTS
3-hydroxy-5,8, 10-pyrenetrisulfonate 相似文献
11.
Spontaneous bleeding of sugar-rich sap from cambial-deep incisions in the bark of trunks was demonstrated for Eucalyptus globulus and other eucalypts across a range of localities and seasonal conditions in south-west Australia. High levels of sucrose
and raffinose (up to 31% w/v total sugars) were present in the exudates, and upward and downward gradients in exudate sugar
concentrations were recorded between samples obtained at different heights up trunks of E. globulus. The data indicated a phloem origin for the exudates, with source:sink pressure gradients driving translocation. Concentration
ratios of sugars to amino acids were consistently lower in exudate from upper (distal) than basal regions of trunks, suggesting
preferential partitioning of nitrogen upwards towards the trunk apex. A comparison of phloem and xylem sap composition from
one plantation over a season showed nitrate in xylem but not phloem and substantial amounts of sodium, and high concentrations
of chloride and sulphate relative to phosphate in xylem and phloem. Phloem sap sampled across a range of 29 contrasting plantations
of E. globulus at peak stress (autumn) showed great inter-site variability in concentrations of amino acids, sulphur, sodium and certain
trace elements and in C:N and Na:K ratios of sap. Carbon isotope ratios (δ13C) were strongly correlated with sugar concentrations of the sap samples from these and other plantations. Use of sap compositional
attributes of phloem and δ13C values of translocated carbon is suggested for assessing the current nutritional condition and water status of E. globulus plantings.
Received: 9 April 1998 / Accepted: 20 August 1998 相似文献
12.
One of the hypotheses proposed for the abscission of flowersand fruits from the cowpea was that the oldest fruits at raceme1 on the peduncle monopolize the mobile nutrients availableto the whole inflorescence. Consequently, the distal young fruitsand flowers starve, abort, and are shed. This hypothesis wastested through autoradiographic studies of the distributionof 14C-assimilates on the cowpea inflorescence and the comparativegrowth of ovaries from persisting and abscising open flowersand young fruits. 14C-asaimilates were distributed to the fruits at raceme 1 andto flower buds, open flowers, and young fruits distal to raceme1. Therefore, the hypothesis that the fruits at raceme 1 monopolizethe mobile assimilates cannot be maintained. At the time of opening the persisting flowers of raceme 1 hadheavier ovaries than the aborting flowers of raceme 3 althoughboth types of flowers were visually alike. During the initial12 h following opening, the difference in ovary size was maintainedand often accentuated. The ovary of the persisting flower increasedin both fresh and dry weights. The growth of the ovary of theaborting flower was variable; the fresh weight often decreased,although it also increased in some experiments; the dry weightremained unchanged or decreased or increased remarkably. The availability of nutrients was considered to be of secondaryimportance in the chain of events leading to fruit abscission.Other internal factors which may control vital processes relatedto embryo development appear to be of primary, underlying importance. 相似文献
13.
Comparative proteomics of cucurbit phloem indicates both unique and shared sets of proteins
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Rosa M. Lopez‐Cobollo Ioannis Filippis Mark H. Bennett Colin G.N. Turnbull 《The Plant journal : for cell and molecular biology》2016,88(4):633-647
Cucurbits are well‐studied models for phloem biology but unusually possess both fascicular phloem (FP) within vascular bundles and additional extrafascicular phloem (EFP). Although the functional differences between the two systems are not yet clear, sugar analysis and limited protein profiling have established that FP and EFP have divergent compositions. Here we report a detailed comparative proteomics study of FP and EFP in two cucurbits, pumpkin and cucumber. We re‐examined the sites of exudation by video microscopy, and confirmed that in both species, the spontaneous exudate following tissue cutting derives almost exclusively from EFP. Comparative gel electrophoresis and mass spectrometry‐based proteomics of exudates, sieve element contents and microdissected stem tissues established that EFP and FP profiles are highly dissimilar, and that there are also species differences. Searches against cucurbit databases enabled identification of more than 300 FP proteins from each species. Few of the detected proteins (about 10%) were shared between the sieve element contents of FP and EFP, and enriched Gene Ontology categories also differed. To explore quantitative differences in the proteomes, we developed multiple reaction monitoring methods for cucumber proteins that are representative markers for FP or EFP and assessed exudate composition at different times after tissue cutting. Based on failure to detect FP markers in exudate samples, we conclude that FP is blocked very rapidly and therefore makes a minimal contribution to the exudates. Overall, the highly divergent contents of FP and EFP indicate that they are substantially independent vascular compartments. 相似文献
14.
The effect of different N supply on amino acid export to the phloem was studied in young plants of wheat (Triticum aestivum L. cv. Klein Chamaco), using the exudation in EDTA technique. Plants were grown in a growth cabinet in pots with sand, and supplied with nutrient solutions of different NO3? concentrations. When plants were grown for 15 days with nutrient solutions containing 1.0, 3.0, 5.0, 10.0, 15.0 or 20.0 mM KNO3, the exudation rate of sugars from the phloem was unaffected by N supply, but sugars accumulated in the leaf tissue when the N supply was limiting for growth. On the other hand, the rate of exudation of amino acids was proportional to the NO3? concentration in the nutrient solution. When the supply of N to plants grown for 15 days with 15.0 mM NO3? was interrupted, the exudation of sugars was again unaffected, but there was a fast decrease in the amount of amino acids exudated, and of the concentration of amino acids and nitrogen in the tissues. Also, when 10-day-old plants grown without N were supplied with 15.0 mM NO3?, there was a sharp increase in the exudation of amino acids, without changes in the amount of sugar exudated. The rate of exudation of amino acids to the phloem was independent of the concentration of free amino acids in the leaves in all three types of experiment. Asp was the most abundant amino acid in the leaf tissue, while Glu was the one most abundant in the phloem exudate. Asp and Ala were exported to the phloem at a rate lower than expected from their leaf tissue concentrations, indicating some discrimination. On the contrary, Glu showed a preferential export at low N supply. It is concluded that the rate of amino acid export from the leaf to the phloem is dependent on the N available to the plant. This N is used for synthesis of leaf protein when the supply is low, exported to the phloem when supply is adequate, and accumulated in the storage pool when supply is above plant demand. 相似文献
15.
Ueda Junichi Miyamoto Kensuke Saniewski Marian Hoshino Tomoki Utsunomiya Maki Okubo Hiroshi 《Acta Physiologiae Plantarum》2002,24(2):187-194
Methyl jasmonate (JA-Me) promoted leaf abscission of succulent plant, Crassula lycopodioides, and exudation from stems and leaves after leaf abscission when it was sprayed in whole plants. Major component of the exudate
was identified as sucrose based on the results described below.
In addition, potassium and sodium were found in the exudate as major inorganic cations. These results suggest that exudate
of Crassula lycopodioides is phloem sap, and JA-Me promotes the excudation due to the inhibition of the synthesis of callose in sieve tubes of succulent
plants. 相似文献
(1) | The reaction of the excudate was not positive in the Somogyi-Nelson method but in the phenol-sulfuric acid method. |
(2) | The exudate was hydrolyzed with invertase of Candida utilis, after that showing a positive reaction in the Somogyi-Nelson method. |
(3) | Only glucose and mannose were identified in the exudate after hydrolysis with trifluoroacetic acid using a gas-liquid chromatograph (GLC). |
(4) | A single peak corresponding to the retention time of sucrose was observed using a high performance liquid chromatograph (HPLC). |
16.
Dry matter accumulation in citrus fruit is not limited by transport capacity of the pedicel 总被引:4,自引:0,他引:4
Garcia-Luis A Oliveira ME Bordon Y Siqueira DL Tominaga S Guardiola JL 《Annals of botany》2002,90(6):755-764
The vascularization of the pedicel in Marisol clementine (Citrus clementina Hort. ex Tanaka) has been characterized in relation to fruit growth. Phloem and xylem formation occurred during the first half of the period of fruit growth. Phloem cross-sectional area reached its maximum value by the end of fruitlet abscission, 78 d after anthesis (DAA), shortly after the rate of accumulation of dry matter in fruitlets reached its maximum value. Secondary xylem formation occurred until day 93, well after the end of fruitlet abscission. At fruit maturity, xylem accounted for 42-46 % of the cross-section of the pedicel. Vessels differentiated in this late-formed xylem. Formation of phloem and early xylem was directly related to fruitlet size (and growth rate). Differences in the rate of formation of conductive tissues in the pedicel of the developing fruitlets followed rather than preceded the differences in growth rate. Specific mass transfer (SMT) in the phloem was highest in the fastest growing fruitlets, and peaked during the late stages of fruitlet abscission (72-78 DAA) and during the main period of fruit growth (107-121 DAA). Application of a synthetic auxin to developing fruits, either at the end of flowering (2,4-D) or by day 64 after flowering (2,4-DP), increased the growth rate of the fruit and fruit size at maturity (8-13 % increase in fruit diameter at maturity). These auxin applications also enhanced the formation of conductive tissues in the pedicel, with a specific effect on phloem formation. Applying auxin at flowering resulted in a reduction in the phloem SMT by days 72-78, whereas auxin application on day 64 increased this parameter. Despite this difference in behaviour, which resulted from the different time-course of the growth response of the fruit to auxin applications, these applications increased fruit size to a similar extent. Severing 37 % of the phloem of the pedicel during the main period of fruit growth resulted in an increase in the specific mass transfer in the phloem but had no influence on fruit growth. These observations demonstrate that the transport capacity in the phloem of the pedicel does not limit fruit growth and, within the limits of our experiments, an increase in demand by the fruit appeared to be matched by an increase in SMT. The dependence of late xylem formation (after the period of fruitlet abscission) on fruitlet growth was demonstrated in Salustiana orange [Citrus sinensis (L.) Osbeck] by means of controlling fruit growth through the manipulation of leaf area. Fruit growth at this time was more closely related to leaf area than to carbohydrate levels, suggesting that it may be limited by current photosynthesis. 相似文献
17.
Olena Tetyuk Urs F. Benning Susanne Hoffmann-Benning 《Journal of visualized experiments : JoVE》2013,(80)
The plant phloem is essential for the long-distance transport of (photo-) assimilates as well as of signals conveying biotic or abiotic stress. It contains sugars, amino acids, proteins, RNA, lipids and other metabolites. While there is a large interest in understanding the composition and function of the phloem, the role of many of these molecules and thus, their importance in plant development and stress response has yet to be determined. One barrier to phloem analysis lies in the fact that the phloem seals itself upon wounding. As a result, the number of plants from which phloem sap can be obtained is limited. One method that allows collection of phloem exudates from several plant species without added equipment is the EDTA-facilitated phloem exudate collection described here. While it is easy to use, it does lead to the wounding of cells and care has to be taken to remove contents of damaged cells. In addition, several controls to prove purity of the exudate are necessary. Because it is an exudation rather than a direct collection of the phloem sap (not possible in many species) only relative quantification of its contents can occur. The advantage of this method over others is that it can be used in many herbaceous or woody plant species (Perilla, Arabidopsis, poplar, etc.) and requires minimal equipment and training. It leads to reasonably large amounts of exudates that can be used for subsequent analysis of proteins, sugars, lipids, RNA, viruses and metabolites. It is simple enough that it can be used in both a research as well as in a teaching laboratory. 相似文献
18.
Interaction of phloem-translocated amino compounds with nitrate net uptake by the roots of beech (Fagus sylvatica) seedlings 总被引:1,自引:0,他引:1
Gebler A; Schultze M; Schrempp S; Rennenberg H 《Journal of experimental botany》1998,49(326):1529-1537
In the present study two experimental approaches were used to investigate
the influence of changes in the allocation of amino compounds in the phloem
of beech (Fagus sylvatica L.) seedlings on nitrate net
uptake by the roots. In a first set of experiments Gin or Asp were directly
fed into the phloem of the epicotyl via bark flaps. These compounds were
previously found to be allocated in the phloem of adult beech trees and
were shown to inhibit nitrate net uptake when supplied to beech roots.
Feeding of solutions containing 100 mM of Gin or Asp plus 10 mM EDTA into
the phloem resulted in a significant enrichment of the fine root tissue
with the amino compound fed as compared to the roots of control plants
supplied with amino acid-free EDTA solutions. Nitrate net uptake by the
roots decreased by 61% (Gin) and 79% (Asp) as compared to the controls. In
a second approach, shoots of young beech seedlings were exposed to
40g NH3 m-3. NH3
uptake by shoots, nitrate net uptake by roots, and the contents and
composition of total soluble non-protein nitrogen (TSNN) in leaves, phloem,
and fine roots were determined and were compared to results gained with
control plants exposed to charcoal-filtered air. NH3 fumigation of the
shoots of beech seedlings resulted in a 35% reduction of nitrate net uptake
by the roots as compared to controls. TSNN contents in leaves and phloem
exudate of NH3-fumigated plants increased by 56% and 37%, respectively.
This enrichment was mainly due to Arg and Glu in the leaves and Asp, Asn,
Glu, and Gin, but not to Arg, in phloem exudate. The TSNN content of the
fine roots was not changed by NH3 fumigation, but a significant increase in
the Gin content was observed. From these results it is concluded that
phloem transport of amino compounds, especially of Gin and Asp, from the
shoot to the roots mediates regulation of nitrate net uptake by the roots
of beech trees in order to adapt this process to the nitrogen demand of the
whole plant. 相似文献
19.
Christian Schobert Lucian Baker Judit Szederkényi Pia Großmann Ewald Komor Hiroaki Hayashi Mitsuo Chino William J. Lucas 《Planta》1998,206(2):245-252
The mature, functional sieve-tube system in higher plants is dependent upon protein import from the companion cells to maintain
a functional long-distance transport system. Soluble proteins present within the sieve-tube lumen were investigated by analysis
of sieve-tube exudates which revealed the presence of distinct sets of polypeptides in seven monocotyledonous and dicotyledonous
plant species. Antibodies directed against sieve-tube exudate proteins from Ricinus communis L. demonstrated the presence of shared antigens in the phloem sap collected from Triticum aestivum L., Oryza sativa L., Yucca filamentosa L., Cucurbita maxima Duch., Robinia pseudoacacia L. and Tilia platyphyllos L. Specific antibodies were employed to identify major polypeptides. Molecular chaperones related to Rubisco-subunit-binding
protein and cyclophilin, as well as ubiquitin and the redox proteins, thioredoxin h and glutaredoxin, were detected in the
sieve-tube exudate of all species examined. Actin and profilin, a modulator of actin polymerization, were also present in
all analyzed phloem exudates. However, some proteins were highly species-specific, e.g. cystatin, a protease-inhibitor was
present in R. communis but was not detected in exudates from other species, and orthologs of the well-known squash phloem lectin, phloem protein
2, were only identified in the sieve-tube exudate of R. communis and R. pseudoacacia. These findings are discussed in terms of the likely roles played by phloem proteins in the maintenance and function of the
enucleate sieve-tube system of higher plants.
Received: 12 February 1998 / Accepted: 16 March 1998 相似文献
20.
Ellis, E. C. and Spanswick, R. M. 1987. Sugar efflux from attachedseed coats of Glycine max (L.) Merr.J. exp. Bot. 38:14701483. Sugar efflux (sucrose + glucose) from attached seed coats ofGlycine max (L.) Merr. was measured at high sampling rates toimprove the kinetic characterization of seed coat exudation.This study confirms that sugar efflux in seed coats has at leasttwo components, and demonstrates that the concentration of mannitolosmoticum bathing the seed coat may influence one or both ofthese components. High leaf irradiance increased sugar effluxrelative to a low leaf irradiance at the same mannitol concentration.A high concentration of mannitol (500 mol m3) enhanced sugarefflux relative to a medium concentration (100 mol m3) underboth high and low leaf irradiance. A low mannitol concentration(10 mol m3) stimulated sugar efflux (relative to 100 mol m3)to a greater extent when leaf irradiance was high. Rapid changesin mannitol concentration produced immediate stimulations ofsugar efflux. Effects of osmoticum on sugar efflux are explainedby simultaneous turgor-mediated effects on import of sucroseby the phloem and retrieval of apoplastic sucrose, presumablyby seed coat parenchyma. 相似文献