Ion Transport into the Xylem

Pitman, M. G.

doi:10.1146/annurev.pp.28.060177.000443

Cited by 129 publications

(80 citation statements)

References 56 publications

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“…This conclusion is based on (a) ultrafilter coefficients of denatured parenchyma slices, (b) the absence of a significant difference between ultrafilter coefficients of the living tissue slices for osmotica with low and high cell wall reflection coefficients, and (c) the absence of a significant interaction (solvent drag) between apoplasmic permeation of mannitol and the water flux caused by a concentration difference of excluded polyethylene glycol. Liquid-filled intercellular spaces were the dominating pathways for pressure-driven volume fluxes through the parenchyma tissue.In textbooks and reviews (Anderson, 1976; Lauchli, 1976;Pitman, 1977), the nonspecialized apoplast is usually considered more permeable to water than the protoplast or the symplast. However, severa1 authors (…”

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confidence: 99%

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confidence: 99%

“…In textbooks and reviews (Anderson, 1976;Lauchli, 1976;Pitman, 1977), the nonspecialized apoplast is usually considered more permeable to water than the protoplast or the symplast. However, severa1 authors (Myers, 1951;Tyree, 1968Tyree, , 1973Molz and Ilkenberry, 1974;Newman, 1976;Tyree and Yanoulis, 1980;Steudle and Jeschke, 1983;Boyer, Ferrier and Dainty, 1977;Steudle and Boyer, 1985) are not rare, but the results are conflicting (see Kramer and Boyer, 1995).…”

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Apoplasmic and Protoplasmic Water Transport through the Parenchyma of the Potato Storage Organ

et al. 1997

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(W.M., A.S., R.E.); and Timiryasev-lnstitute of Plant Physiology, Russian Academy of Sciences, 127 276 MOSCOW, Botanicheskaya Ulica, 35, Russia (A.B.M.) Stationary volume fluxes through living and denatured parenchyma slices of the potato (Solanum tuuberosum L.) storage organ were studied to estimate the hydraulic conductivity of the cell wall and to evaluate the significance of water transport through protoplasts, cell walls, and intercellular spaces. Slices were placed between liquid compartments, steady-state fluxes induced by pressure or concentration gradients of low-and high-molecular-mass osmotica were measured, and water transport pathways were distinguished on the basis of their difference in limiting pore size. The protoplasts were the dominating route for osmotically driven water transport through living slices, even in the case of a polymer osmoticum that is excluded from cell walls. The specific hydraulic conductivity of the cell wall matrix is too small to allow a significant contribution of the narrow cell wall bypass to water flow through the living tissue. This conclusion is based on (a) ultrafilter coefficients of denatured parenchyma slices, (b) the absence of a significant difference between ultrafilter coefficients of the living tissue slices for osmotica with low and high cell wall reflection coefficients, and (c) the absence of a significant interaction (solvent drag) between apoplasmic permeation of mannitol and the water flux caused by a concentration difference of excluded polyethylene glycol. Liquid-filled intercellular spaces were the dominating pathways for pressure-driven volume fluxes through the parenchyma tissue.In textbooks and reviews (Anderson, 1976; Lauchli, 1976;Pitman, 1977), the nonspecialized apoplast is usually considered more permeable to water than the protoplast or the symplast. However, severa1 authors (

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Apoplasmic and Protoplasmic Water Transport through the Parenchyma of the Potato Storage Organ

et al. 1997

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“…The radial pathway for N03-movement in the root thus likely would involve uptake by epidermal or outer cortical cells at the root periphery, symplastic transport through the cortex and stele, and release from the symplasm into the xylem at xylem parenchyma cells (6,9,16,27). Accordingly, a possible explanation for limited reduction of endogenous NO3-is that NR is localized predominantly in cells at the root periphery.…”

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Intercellular Localization of Nitrate Reductase in Roots

Rufty¹,

Thomas²,

Remmler³

et al. 1986

Plant Physiol.

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Experiments were conducted with segments of corn roots to investigate whether nitrate reductase (NR) is compartmentalized in particular groups of cells that collectively form the root symplastic pathway. A microsurgical technique was used to separate cells of the epidermis, of the cortex, and of the stele. The presence of NR was determined using in ritro and enzyme-linked immunosorbent assays. In roots exposed to 0.2 millimolar N03-for 20 hours, NR was detected almost exclusively in epidermal cells, even though substantial amounts of NO3-likely were being transported through cortical and steler cells during transit to the vascular system. Although NR was present in all cell groups of roots exposed to 20.0 millimolar NO3-, the majority of the NR still was contained in epidermal cells. The results are consistent with previous observations indicating that limited reduction of endogenous NO3-occurs during uptake and reduction of exogenous NO3-. Several mechanisms are advanced to account for the restricted capacity of cortical and stelar cells to induce NR and reduce NO3-. It is postulated that (a) the biochemical system involved in the induction of NR in the cortex and stele is relatively insensitive to the presence of NO3-, (b) the receptor for the NR induction response and the NR protein are associated with cell plasmalemmae and little NO3-is taken up by cells of the cortex and stele, and/or (c) N03-is compartmentalized during transport through the symplasm, which limits exposure for induction of NR and NO3-reduction.Experiments with wheat and corn seedlings using 15N03-have revealed that NO3-reduction in roots may be localized in a specific cellular compartment (1,17,18). Following induction of the N03 transport and reduction systems, exogenously supplied NO3-being taken up by the root was readily reduced and translocated to the xylem. In contrast, endogenous NO3-which had been previously accumulated in the tissue was readily translocated or effluxed to the external solution, but minimal amounts were reduced.

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“…Accumulative uptake ofP by root cortical and rhizome cells must be followed by transfer to the xylem. Although a case has been described for a diffusive release of ions into the xylem vessels (Dunlop & Bowling, 1971), most current evidence supports a release which is energy-dependent (Pitman, 1977). This energy source is ATP (Raven, 1974); in the dark this is supplied by oxidative phosphorylation and in the light, in addition, by the photophosphorylation.…”

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Light-dependent uptake, translocation and foliar release of phosphorus by the intertidal seagrass Zostera noltii Hornem.

Pérez-Lloréns

Visscher

Nienhuis

et al. 1993

Journal of Experimental Marine Biology and Ecology

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Light-dependent P uptake by root-rhizomes, acropetal translocation and subsequent foliar release by Zostera noltii Hornem. was studied under laboratory conditions in two-compartment chambers using 32p. The uptake by underground parts was unaffected by light conditions but the acropetal translocation proceeded more rapidly in light than in dark, indicating a coupling to the metabolic activity of the plants. The translocated P was mainly accumulated in the youngest leaves (30%), i.e., the most actively growing parts.Foliar release of P might be considered negligible (2-4 % of the P taken up by root-rhizomes), indicating that the role of Z. noltii as a "P pump" is of minor importance in the cycling of P between sediment and water. This was calculated for part of the Oosterschelde estuary, Zeeland, The Netherlands.

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Ion Transport into the Xylem

Cited by 129 publications

References 56 publications

Apoplasmic and Protoplasmic Water Transport through the Parenchyma of the Potato Storage Organ

Apoplasmic and Protoplasmic Water Transport through the Parenchyma of the Potato Storage Organ

Intercellular Localization of Nitrate Reductase in Roots

Light-dependent uptake, translocation and foliar release of phosphorus by the intertidal seagrass Zostera noltii Hornem.

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