Suberized bundle sheaths in grasses (Poaceae) of different photosynthetic types. II. Apoplastic permeability

Eastman, P. Ann K.; Peterson, Carol A.; Dengler, Nancy G.

doi:10.1007/bf01290868

Cited by 33 publications

(9 citation statements)

References 54 publications

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“…2). Like sucrose, the PTS molecule is reported to be about lnm in diameter (Eastman et al 1988). So, if PTS can readily move through the apoplasm of the storage parenchyma of tomato fruit, it is likely that sucrose, as well as glucose and fructose, are equally mobile.…”

Section: Discussionmentioning

confidence: 99%

The cellular pathway of postphloem sugar transport in developing tomato fruit

Ruan

Patrick

1995

Planta

172

161

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Abstract. The cellular pathway of postphloem sugar transport was elucidated in the outer pericarp of tomato (Lycopersicon esculentum Mill cv. Floradade) fruit at 13-14 and 23-25 days after anthesis (DAA). These developmental stages are characterized by phloem-imported sugars being accumulated as starch and hexose, respectively. The symplasmic tracer, 5(6)-carboxyfluorescein, loaded into the storage parenchyma cells of pericarp discs, moved readily in the younger fruit but was immobile in fruit at 23-25 DAA. Symplasmic mobility of [14C]glucose was found to be identical to 5(6)-carboxyfluorescein. For the older fruit, the pericarp apoplasm was shown to be freely permeable to the apoplasmic tracer, trisodium 3-hydroxy-5,8,10-pyrenetrisulfonate. Indeed, the transport capacity of the pericarp apoplasm was such that the steady-state rate of in-vitro glucose uptake by pericarp discs accounted fully for the estimated rate of in-vivo glucose accumulation. For fruit at 23-25 DAA, the inhibitory effects of the sulfhydryl group modifier, p-chloromercuribenzenesulfonic acid (PCMBS), on [14C]glucose and [14C]fructose uptake by the pericarp discs depended on the osmolality of the external solution. The inhibition was most pronounced for pericarp discs enriched in storage parenchyma. Consistent with the PCMBS study, strong fluorescent signals were exhibited by the storage parenchyma cells of pericarp discs exposed to the membrane-impermeable thiol-binding fluorochrome, monobromotrimethylammoniobimane. The fluorescent weak acid, sulphorhodamine G, was accumulated preferentially by the storage parenchyma cells. Accumulation of sul- (ii) An energy-coupled plasma-membrane hexose carrier is expressed specifically in storage parenchyma cells at the latter stage of fruit development.

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Section: Discussionmentioning

confidence: 99%

The cellular pathway of postphloem sugar transport in developing tomato fruit

Ruan

Patrick

1995

Planta

172

161

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“…It has been reported that phenolics in lignin or nonpolymeric phenols may affect the mobility of tracers used to follow the apoplastic permeability of different tissues (Eastman et al 1988). These authors also emphasized that the electric charge (particularly positive) of the tracer may restrict its diffusion through the tissues by interacting with carboxyl groups of phenolic compounds.…”

Section: Permeability Testsmentioning

confidence: 97%

Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. I. Anatomy and histochemistry

Rioux¹,

Ouellette²

1991

Can. J. Bot.

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R~o u x , D., and OUELLEWE, G. B. 1991. Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. I. Anatomy and histochemistry. Can. J. Bot. 69: 205552073, Barrier zone formation was studied in small branches of Ulmus americana L., Prunus pensylvanica L.f., and Popillus balsamifera L. following inoculation with Ophiostoma ulmi (Buism.) Nannf. (the Dutch elm disease pathogen). Barrier zones were continuous in the nonhosts whereas they were generally discontinuous in U. americana; barrier zone formation also occurred at a later stage of infection in the latter than in the former. Barrier zones were formed of parenchyma cells and fibers in U. americana, mainly of parenchyma cells in Prunus pensylvanica, and of fibers in Populus balsamifera. Fibers as a principal component of barrier zones are described for the first time. Histochemical tests revealed that the proportion of lignin was higher in barrier zone cell walls than in elements of the noninvaded xylem. Barrier zones contained suberized cells, the number of which was progressively greater in the order U. americana, Prunus perzsylvanica, and Populus balsamifera. However, many fibers of U. americana occasionally formed a continuous barrier zone and had an internal layer that was slightly suberized. In addition, phenolic compounds were usually detected within barrier zone cells of these species.

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“…It may have some impact whenever pressure signals are moving within the plant, such as during changes in transpiration or during injury (Malone, 1996). This is true, although there are usually no structures in the shoot which are really comparable with the endodermis (such as suberized bundle sheaths; Eastman et al ., 1988).…”

Section: Discussionmentioning

confidence: 99%

Effects of water storage in the stele on measurements of the hydraulics of young roots of corn and barley

2009

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Summary• In standard techniques (root pressure probe or high-pressure flowmeter), the hydraulic conductivity of roots is calculated from transients of root pressure using responses following step changes in volume or pressure, which may be affected by a storage of water in the stele.• Storage effects were examined using both experimental data of root pressure relaxations and clamps and a physical capacity model. Young roots of corn and barley were treated as a three-compartment system, comprising a serial arrangement of xylem/probe, stele and outside medium/cortex. The hydraulic conductivities of the endodermis and of xylem vessels were derived from experimental data. The lower limit of the storage capacity of stelar tissue was caused by the compressibility of water. This was subsequently increased to account for realistic storage capacities of the stele.• When root water storage was varied over up to five orders of magnitude, the results of simulations showed that storage effects could not explain the experimental data, suggesting a major contribution of effects other than water storage.• It is concluded that initial water flows may be used to measure root hydraulic conductivity provided that the volumes of water used are much larger than the volumes stored. Abbreviations:A end , surface area of endodermis; A x , surface area of xylem vessel walls; C/D model, convection/diffusion model; EMX, early metaxylem; HPFM, highpressure flowmeter;, water flux across endodermis; , water flux across EMX vessel walls;, water flux across LMX (late metaxylem) vessel walls; k f , rate constant of fast phase of pressure profile; k s , rate constant of slow phase of pressure profile; Lp r , overall hydraulic conductivity of root;, hydraulic conductivity of endodermis;, hydraulic conductivity of xylem vessel walls; PC, pressure clamp; PR, pressure relaxation; PR reg , regressive average of pressure relaxation curve;, amplitude of fast phase of pressure profile; , amplitude of slow phase of pressure profile; ΔP r , amplitude of applied pressure change during a pressure relaxation and pressure clamp experiment; P r , pressure in xylem/probe system; P ro , equilibrium root pressure;, pressure in stelar apoplast; , permeability coefficient of endodermis; RPP, root pressure probe;, half-time of fast phase of the pressure profile;, half-time of slow phase of the pressure profile; USL, unstirred layer; V st , volume of stelar compartment; V S , volume of probe/xylem system; V x , volume of xylem vessels; β, elastic modulus of system (xylem plus RPP); γ, elastic moduli of stelar compartment; κ w , compressibility of water;, reflection coefficient of endodermis.

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Suberized bundle sheaths in grasses (Poaceae) of different photosynthetic types. II. Apoplastic permeability

Cited by 33 publications

References 54 publications

The cellular pathway of postphloem sugar transport in developing tomato fruit

The cellular pathway of postphloem sugar transport in developing tomato fruit

Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. I. Anatomy and histochemistry

Effects of water storage in the stele on measurements of the hydraulics of young roots of corn and barley

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