Transport symplastem Transport floémem

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1 Transport symplastem Transport floémem
Biologická fakulta Jihočeské Univerzity Katedra fyziologie a anatomie rostlin Kurz fyziologie rostlin Transport v rostlinách 2 Ivan Šetlík Transport symplastem Transport floémem

2 cytosol plasmodesmata vakuola buněčná stěna mezibuněčný prostor
(3) BMBP Fig Diagram of the apoplast/symplasm concept. Soluted may move through the tissue via an apoplastic pathway (cell walls, in red) or symplasmic pathway (connected cytoplasmic contentrs of the cells (blue). Most solutes cannot readily cross the tonoplast vacuoles are usually not regarded as part of the symplasm.

3 desmotubul s centrální tyčinkou
sleeve (4) BMBP Fig (A) Electron micrographs of plasmodesmata in longitudinal and cross-sections, accompanied by the terminology applied to frequently observed structural features. (B) A model of plasmodesmal substructure based on observations of freeze-substituted tobacco leaves. The plasma membrane and endoplasmic reticulum are continuous cell to cell, with the latter tightly furled (svinout) to form the desmotubule. A sleeve of cytoplasm (the Cytoplasmic annulus, in cross-section) occupies the gap between the plasma membrane and desmotubule; in the right plasmodesma, the sleeve has enlarged to form a central cavity. Much of the Cytoplasmic annulus is occluded by proteinaceous particles partially embedded in the plasma membrane and the desmotubule. Gaps between these particles evidently represent the physical basis for the molecular sieving properties of symplasmic transport. Within the central cavity, spoke-like structures extend across the Cytoplasmic sleeve; their presence in the neck region is unclear. plasmová membrána prsténec cytoplasmy desmotubul s centrální tyčinkou Centrální tyčinka Cytoplasmový rukávec centrální dutina

4 (5) BMBP Fig "Squeezing" of the ER lumen by the cell plate during formation of primary plasmodesmata. The densely stained ER lumen disappears where ER traverses the cell plate (*).

5 podnož roub (7) BMBP Fig Formation of secondary plasmodesmata during a graft union. [A] first evidence of coming fusion ER becomes adnated to the plasma membrane. [D - F] after ER and plasma membrane have fused the cell wall redeposits much as it does during thickening of the cell plate after cell division.

6 (6) BMBP Plasmodesmal morphology takes on several forms, but the functional significance of this variation is unknown.The hatched regions indicate ER in its appreseed, or desmotubule, form.

7 (8) BMBP Fig Rates of cell-to-cell solute movement much higher than expected for transmembrane transport implicate plas-modesmata as the pathway for movement. In these three examples, the transport interface for the measured fluxes is indicated in red.

8 (9) BMBP Fig Conceptual models for the cell-to-cell trafficking of viral RNA (vRNA). Presumably, a similar process applies to the trafficking of native RNA in uninfected plants. Both models involve unfolding of the RNA as an essential step in transport. Model I: Movement protein (MP) binds to vRNA, and the MP-vRNA complex moves through the plasmodesma. Model II: In addition to MP, this model postulates the involvement of endogenous plant cell proteins in vRNA trafficking. Both endogenous binding protein (BP) and MP are included in the ribonucleoprotein complex, which may also include a cytosolic receptor protein (Re). At the plasmodesmal orifice, a stationary docking protein (D), perhaps also involved in gating of the MEL or the unfolding of the RNA (or both), initiates the export process and the receptor is recycled. On the importing side, another cytosolic receptor (R;) recognizes and imports the complex. CW, cell wall.

9 (10) BMBP Fig A conceptual model for cell-to-cell trafficking of specific proteins of a size larger than the passive SEL (size exclusion limit). After binding to a chaperone, the protein-chaperone complex interacts with a plasmodesmal receptor site and moves to the plasmodesmal orifice. There, the complex binds to a site that up-regulates the plasmodesmal SEL. Before or upon reaching the SEL binding site, the protein unfolds to a more linear form for passage through the plasmodesmal microchannel. (Proteins smaller than the plasmodesmal SEL may move without unfolding or other specific interaction with the plasmodesma.) CW, cell wall.

10 The transmitted signal is gene specific and, from earlier work, is almost certainly some form of RNA. BMBP Fig Figure 15.62 In a phenomenon termed "systemic acquired silencing," cosuppression of the nitrate reductase gene in tobacco is transmitted from a suppressed stock to a nonsuppressed scion. In this experiment, the apex of a nonsuppressed plant is grafted onto a suppressed stock. Transmission of the gene silencing effect can be followed visually, because suppression of the nitrate reductase gene causes marked chlorosis of the affected leaves. The transmitted signal is gene specific and, from earlier work, is almost certainly some form of RNA.

11 Mohr-Schopfer Fig Top A cocklebur plant (Xanthium strumarium) with two shoots. The shaded area was subjected to short days and the rest of the plant to long days. Both shoots flower if the short-day shoot is not completely defoliated. An eighth of a leaf suffices for induction (centre). Below Two Xanthium plants were grafted together (for the technique of grafting, see Fig ). The shaded area received short-day treatment. It is obvious that florigen passed via the graft union (left). F Flowering; V vegetative shoot. (After Hamner 1942)

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13 jímky jímky zdroje jímky zdroje xylém floém jímky jímka

14 jednoděložná rostlina
rhizoermis kůra endodermis stélé jednoděložná rostlina dvouděložná rostlina endodermis pericykl floem xylem dřeň (15) PoHoVe_Bi_29-12 Text in the figure Casparyho proužek v o d a rozpuštěné látky Buňky endodermis

15 exodermis kůra endodermis pericykel
periderm primární floém sekundární floém sekund. kambium sekundární xylém primární xylém primární floém sekundární kambium primární xylém paprsek primárního parenchymu exodermis kůra endodermis pericykel primární xylém primární floém sekundární xylém

16 centrální cylindr (stélé)
epidermis kůra dřeň (duše) svazek cévní dvouděložná rostlina floém mezisvazkové kambium xylém

17 jednoděložná rostlina
epidermis dřeň (duše) kůra svazek cévní jednoděložná rostlina floém xylém

18 soja (Glycine max) floémové sítkovice průvodní buňka sítkovice
průřez osou floém xylémové cévy kambium xylém (18) Detail 17; BMBP Fig Text nevkládat sem, ale na zvláštní stránku. xylémový parenchym cévy

19 průřez koncovou žilkou v listu
průřez listem svrchní epidermis palisádový parenchym houbový parenchym spodní epidermis endodermis kůra epidermis xylémové cévy (19) Detail 17. BMBP Fig Text nevkládat sem, ale na zvláštní stránku. floémovésítkovice a Průvodní buňky průřez kořenem průřez koncovou žilkou v listu průřez vodivým svazkem v kořenu

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21 Sítkovicové články

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24 sítkovice sítko průvodní buňky
Figure THE ORGANIZATION OF VASCULAR TISSUE: PHLOEM. Phloem is composed primarily of sieve tube elements, with their perforated end walls (sieve plates). The closely associated living companion cells are visible, with their cytoplasm and nuclei.

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26 BMBP Fig Figure 15.40 Companion cell (CC) and a sieve element (SE) are connected by a pore-plasmodesma complex consisting of a pore in the sieve element wall linked via a central cavity to multiple plasmodesmata in the companion cell wall (CW). ER, endoplasmic reticulum.

27 zprostředkující buňka
Taiz & Zeiger, 2nd edition. Figure Electron micrographs of companion cells in minor veins of mature leaves. (A) A minor vein from Mimulus cardinalis (6585x) Three sieve elements abut two intermediary cells and a more lightly stained ordinary companion cell. (B) A transfer cell and a sieve element from pea (Pisum sativum). (8020x) Note the numerous wall ingrowths on the walls of the transfer cell that are adjacent to the parenchyma cells but not on the wall opposite the sieve element. Such ingrowths greatly increase the surface area of the transfer cell's plasma membrane, thus increasing the potential for solute transport and ultimately facilitating the transfer of materials from the mesophyll to the sieve elements. Note the presence of plasmodesmata between the transfer cell and the sieve element. (C) Minor-vein phloem from heartleaf maskflower (Alonsoa warscewiczil). (4700x) Note the typical intermediary cell with numerous fields of plasmodesmata (arrows) connecting it to neighboring bundle sheath cells. These plasmodesmata are branched on both sides, but the branches are longer and more narrow on the intermediary cell. The intermediary cells also have numerous small vacuoles and chloroplasts that lack internal membranes. (A and C from Turgeon et al. 1993, courtesy of R. Turgeon; B from Brentwood and Cronshaw 1978.) běžné průvodní buňky zprostředkující buňka sítkovice

28 transferová průvodní buňka sítkovice
vchlípeniny buněčné stěny transferová průvodní buňka plasmodesmata sítkovice Buňka parenchymu Taiz & Zeiger, 2nd edition. Figure Electron micrographs of companion cells in minor veins of mature leaves. (A) A minor vein from Mimulus cardinalis (6585x) Three sieve elements abut two intermediary cells and a more lightly stained ordinary companion cell. (B) A transfer cell and a sieve element from pea (Pisum sativum). (8020x) Note the numerous wall ingrowths on the walls of the transfer cell that are adjacent to the parenchyma cells but not on the wall opposite the sieve element. Such ingrowths greatly increase the surface area of the transfer cell's plasma membrane, thus increasing the potential for solute transport and ultimately facilitating the transfer of materials from the mesophyll to the sieve elements. Note the presence of plasmodesmata between the transfer cell and the sieve element. (C) Minor-vein phloem from heartleaf maskflower (Alonsoa warscewiczil). (4700x) Note the typical intermediary cell with numerous fields of plasmodesmata (arrows) connecting it to neighboring bundle sheath cells. These plasmodesmata are branched on both sides, but the branches are longer and more narrow on the intermediary cell. The intermediary cells also have numerous small vacuoles and chloroplasts that lack internal membranes. (A and C from Turgeon et al. 1993, courtesy of R. Turgeon; B from Brentwood and Cronshaw 1978.)

29 buňka lýkového parenchymu buňky pochvy zprostředkující průvodní buňky
sítkovice zprostředkující průvodní buňky buňky pochvy cévního svazku buňka lýkového parenchymu Taiz & Zeiger, 2nd edition. Figure Electron micrographs of companion cells in minor veins of mature leaves. (A) A minor vein from Mimulus cardinalis (6585x) Three sieve elements abut two intermediary cells and a more lightly stained ordinary companion cell. (B) A transfer cell and a sieve element from pea (Pisum sativum). (8020x) Note the numerous wall ingrowths on the walls of the transfer cell that are adjacent to the parenchyma cells but not on the wall opposite the sieve element. Such ingrowths greatly increase the surface area of the transfer cell's plasma membrane, thus increasing the potential for solute transport and ultimately facilitating the transfer of materials from the mesophyll to the sieve elements. Note the presence of plasmodesmata between the transfer cell and the sieve element. (C) Minor-vein phloem from heartleaf maskflower (Alonsoa warscewiczil). (4700x) Note the typical intermediary cell with numerous fields of plasmodesmata (arrows) connecting it to neighboring bundle sheath cells. These plasmodesmata are branched on both sides, but the branches are longer and more narrow on the intermediary cell. The intermediary cells also have numerous small vacuoles and chloroplasts that lack internal membranes. (A and C from Turgeon et al. 1993, courtesy of R. Turgeon; B from Brentwood and Cronshaw 1978.)

30 P-protein kalosa C

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32 BMBP Box 15. 2 Collecting exudate from severed aphid stylets comes closest to being an ideal method for sampling sieve tube contents. Aphids and other phloem-feeding insects feed by inserting their mouth parts (stylets) into a sieve tube (panel D). The stylet bundle may be cut by radiofrequency micro-cautery, as illustrated in panel E. Several seconds elapsed between each of the first four frames. In the first, the microcautery probe tip has not yet touched the insect's labium (a sheath around the stylet bundle). In the second, the stylet has just been cut. A drop of hemolymph appears in the third, and the stylet begins to exude after the aphid pulls away in the fourth. After a minute has elapsed (fifth frame), the drop is much larger, although most of the water evaporates rapidly.

33 medovice sítkovice sosák mšice
Figure Collection of phloem sap using aphids, which tap single sieve elements. (A) An aphid (Longistigma caryae) feeding on a branch of linden (Tilia americana). The insect is just releasing a droplet of honeydew, which it does about once every 30 minutes. The honeydew excreted by the aphid consists of sieve element sap from which selected solutes have been removed in the gut of the insect. The high turgor pressure in the sieve element forces the cell contents through the food canal of the aphid and into its gut. (B) Transverse section through the bark of linden, showing the tips of aphid stylets that had been exuding before they were sectioned. The tips of the stylets are inside a single sieve element; the sheath of saliva secreted by the aphid ends outside the cell. (From Zimmermann and Brown 1971.) medovice sosák mšice sítkovice

34 Složení floémové šťávy u skočce a tykve.

35 Obsah volných aminokyselin a amidů
ve floémové šťávě yuky (Yucca flaccida). Hodnoty v molárních procentech

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39 větvička uzavřena ve skleněné lahvi
hlavní větev vrby opatřena chladící trubicí scintilační detektor měří aktivitu cirkulujícího vzduchu v lahvi se generuje 14CO2 který cirkuluje lahví s větvičkou chladící šroubovice teplota aktivita floémové šťávy v sítkovicích větve BMBP Fig aktivita [dpm x 10-6] vzdálenost [cm]

40 buňka floémového parenchymu
sacharid apoplastová cesta sítkovice průvodní buňky sacharid aktivní plnění symplastová cesta sacharid buňka floémového parenchymu PP10142.jpg buňka pochvy svazku cévního mezofylová buňka plasmová membrána

41 komplex průvodní buňky a sítkovice
buňka floémového parenchymu plazmová membrána Buněčná stěna Symport sacharózy s protony PP10160.jpg sacharóza sacharóza vysoká koncentrace protonů nízká koncentrace protonů

42 sacharóza rafinóza stachyóza verbaskóza galaktóza galaktóza galaktóza glukóza fruktóza

43 buňka pochvy svazku cévního zprostředkující průvodní buňka
sítkovice glukóza galaktóza fruktóza sacharóza sacharóza rafinóza plasmodesmata PP10170.jpg

44 BMBP Fig A (A) Experimental setup for monitoring sugars in the apoplast of a translocating sugar beet leaf. Half of the leaf is visible; the other half has been cut away to show the lower chamber (1) through which air containing 14 CO2 was circulated. After the upper epidermis was lightly abraded, the upper (u) and lower chambers were sealed and various solutions were circulated over the upper leaf surface by a pump (p). The translocation rate was monitored continually by the arrival rate of 14C-containing photosynthate in a sink leaf. A sampling rube (s) was used to remove aliquots of circulating solution for assay.

45 buňka mezofylu buňka mezofylu buňka mezofylu buňka mezofylu
14C sacharóza BMBP Fig B

46 rychlost transportu [mg(C) dm2 min -1]
rychlost fotosyntézy [mg(C) dm2 min -1] BMBP Fig C

47 0 mM sacharóza 100 mM sacharóza Čas [min] BMBP Fig. 15.44 Figure 15.44
Supplying sucrose via the apoplast causes a sharp depolarization of the sieve tube membrane potential, suggesting a H+-sucrose cotransport mechanism. An exuding aphid stylet was used to monitor the sieve tube membrane potential in a strip of bark from a willow branch. Introduction of 100 mM sucrose into the solution bathing the cambial surface was followed several minutes later by sucrose-free solution. 100 mM sacharóza Čas [min]