Water Transport in the Midrib Tissue of Maize Leaves

Westgate, Mark E.; Steudle, Ernst

doi:10.1104/pp.78.1.183

Cited by 44 publications

(20 citation statements)

References 19 publications

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“…Lp px not only reflects the permeability of tissue to water, but also the resistance by yielding walls to the growth-induced water flux (Lockhart, 1965). This could also explain the discrepancy between our own estimation and those published by Steudle & Boyer (1984) and Westgate & Steudle (1985).…”

Section: Radial Hydraulic Conductivity and Water Deposition Rate Aloncontrasting

confidence: 56%

“…2), Lp px was close to 6.5 mmol s −" m −# MPa −" . This is about five times lower than values reported in growing sections of soybean hypocotyls (37p24 mmol m −# s −" MPa −" ) by Steudle & Boyer (1984), and about 70 times lower than values reported in midrib tissue of mature maize leaves (494p311 mmol m −# s −" MPa −" ) by Westgate & Steudle (1985). Nevertheless, these authors concluded that the method they used probably largely resulted in an overestimation.…”

Section: Radial Hydraulic Conductivity and Water Deposition Rate Aloncontrasting

confidence: 48%

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Changes in axial hydraulic conductivity along elongating leaf blades in relation to xylem maturation in tall fescue

2000

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Xylem maturation in elongating leaf blades of tall fescue (Festuca arundinacea) was studied using staining and microcasting. Three distinctive regions were identified in the blade : (1) a basal region, in which elongation was occurring and protoxylem (PX) vessels were functioning throughout ; (2) a maturation region, in which elongation had stopped and narrow (NMX) and large (LMX) metaxylem vessels were beginning to function ; (3) a distal, mature region in which most of the longitudinal water movements occurred in the LMX. The axial hydraulic conductivity (K h ) was measured in leaf sections from all these regions and compared with the theoretical axial hydraulic conductivity (K t ) computed from the diameter of individual inner vessels. K t was proportional to K h throughout the leaf, but K t was about three times K h . The changes in K h and K t along the leaf reflected the different stages of xylem maturation. In the basal 60 mm region, K h was about 0.30p0.07 mmol s −" mm MPa −" . Beyond that region, K h rapidly increased with metaxylem element maturation to a maximum value of 5.0p0.3 mmol s −" mm MPa −" , 105 mm from the leaf base. It then decreased to 3.5p0.2 mmol s −" mm MPa −" near the leaf tip. The basal expanding region was observed to restrict longitudinal water movement. There was a close relationship between the water deposition rate in the elongation zone and the sum of the perimeters of PX vessels. The implications of this longitudinal vasculature on the partitioning of water between growth and transpiration is discussed.

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Section: Radial Hydraulic Conductivity and Water Deposition Rate Aloncontrasting

confidence: 56%

Section: Radial Hydraulic Conductivity and Water Deposition Rate Aloncontrasting

confidence: 48%

Changes in axial hydraulic conductivity along elongating leaf blades in relation to xylem maturation in tall fescue

2000

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“…One path may present much more resistance to flow than the other, and the path taken may depend on the nature of the force driving water movement. In corn midrib, for example, when the driving force is osmotic (as in open pulvini), water movement is confined to the cell-to-cell route; when a pressure gradient is present (as in closed pulvini), a much more rapid, apoplastic route becomes available (26 Hydrostatic Pressure. In order for a pulvinus, a nongrowing organ, to close, P must increase in the flexor relative to the extensor.…”

Section: Discussionmentioning

confidence: 99%

Water Relations in Pulvini from Samanea saman

Gorton

1987

Plant Physiol.

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Biological Sciences Group U-42, University ofConnecticut, Storrs, Connecticut 06268 ABSTRACI The movement of Samwaea leaflets depends upon changes in the curvature of the pulvinus at the base of each leaflet. Pulvinar bending and straightening, in turn, are driven by the movement of water between opposing (extensor and flexor) sides of the pulvinus. Although water movement depends on water potential (1) and thus on osmotic potential (X) and hydrostatic pressure (P), none of these parameters have been measured in Samauea. In this investigation, il and X were measured and P was calculated for extensor Leaves and leaflets of the nyctinastic, leguminous tree Samanea saman (Jacq.) Merrill3 are usually spread horizontally during the day and folded tightly into a vertical orientation at night (2,20). These movements are brought about by the bending and straightening ofcylindrical motor organs, or pulvini, that subtend the leaf, the pinnae and the pinnules (see Fig. 2 (12,13,19). However, the magnitude and direction of the H+ fluxes varies with the 74 of the medium (16). These results are suggestive of a turgor-sensing mechanism, but they are difficult to interpret because we know very little about the I on the extensor and flexor sides of the pulvinus. If these in vitro experiments are to have maximum relevance to events occurring in whole pulvini, we must be able to design an appropriate bathing medium, with 7r balanced against the tissue , and we must understand the effects of excision.Pulvinar bending depends upon water movement, and thus on the I, wr, and P on the two sides of the pulvinus. regime at 27°C, as described in Gorton and Satter (10). Terminal secondary pulvini were used for all experiments. A protractor was used to measure leaflet angles (the angle between the rachis and the rachilla).Osmolality Measurements. Fluid from extensor and flexor tissues was obtained by two methods.1. Strips ofextensor and flexor tissue were excised as described in Iglesias and Satter (12). The tissue strips were squashed between a glass slide and a stainless steel spatula, and expressed fluid was collected with a glass microcapillary, all within a 4Abbreviations: ir = osmotic potential; PEG = polyethylene glycol (mol wt 3350); P = hydrostatic pressure; 1 = water potential (+ = r + P). 945www.plantphysiol.org on May 11, 2018 -Published by Downloaded from

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“…Nonami and Boyer, 1990). An increase in P, converts to a transient turgor pressure increase (Westgate and Steudle, 1985;Malone and Stankovic, 1991;Frensch and Hsiao, 1994) and then results in a transient depolarization. The application of a pressure step of 30 kPa to the root xylem converts to a AP, of only 25 kPa at position B of the pea epicotyl, which sufficed to induce a depolarization in the epidermis cells.…”

Section: Dlscusslon the Pressure Sensitivity Of Epicotyl Cellsmentioning

confidence: 99%

The Propagation of Slow Wave Potentials in Pea Epicotyls

1997

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Slow wave potentials are considered to be electric long-distance signals specific for plants, although there are conflicting ideas about a chemical, electrical, or hydraulic mode of propagation. These ideas were tested by comparing the propagation of hydraulic and electric signals in epicotyls of pea (Pisum sativum 1). A hydraulic signal in the form of a defined step increase in xylem pressure (P,) was applied to the root of intact seedlings and propagated nearly instantly through the epicotyl axis while its amplitude decreased with distance from the pressure chamber. This decremental propagation was caused by a leaky xylem and created an axial P, gradient in the epicotyl. Simultaneously along the epicotyl surface, depolarizations appeared with lag times that increased acropetally with distance from the pressure chamber from 5 s to 3 min. When measured at a constant distance, the lag times increased as the size of the applied pressure steps decreased. We conclude that the P, gradient in the epicotyl caused local depolarizations with acropetally increasing lag times, which have the appearance of an electric signal propagating with a rate of 20 to 30 mm min-'. This static description of the slow wave potentials challenges its traditional classification as a propagating electric signal.SWPs, also called variation potentials, have been reported and described in a variety of different plant species, first in seismonastic plants such as Mimosa pudica (Houwinck, 1935;Sibaoka, 1953;Umrath, 1959;Roblin and Bonnemain, 1985) and later in a variety of common or nonseismonastic plants (Kawano, 1955;Van Sambeek et al., 1976;Tsaplev and Zatsepina, 1980; Frachisse et al., 1985;Roblin and Bonnemain, 1985;Wildon et al., 1992; Davies et al., 1991; Boari and Malone, 1993). Like the better-known APs, SWPs are considered to be electric long-distance signals in plants. In M. pudica, Bidens pilosa, Tradescantia, Vicia faba, and many other plants, both electric signals occur together. Usually an AP spike precedes the development of the SWP, indicating a faster rate of propagation for APs (Houwinck, 1935; Davies et al., 1991). These rates also determine the spike-like appearance of APs and the wave-like appearance of SWPs in extracellular recordings.APs are induced by the coordinated activity of ion channels (Wayne, 1994), and their propagation in both plants and animals is considered to be electrotonic (e.g.

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Water Transport in the Midrib Tissue of Maize Leaves

Cited by 44 publications

References 19 publications

Changes in axial hydraulic conductivity along elongating leaf blades in relation to xylem maturation in tall fescue

Changes in axial hydraulic conductivity along elongating leaf blades in relation to xylem maturation in tall fescue

Water Relations in Pulvini from Samanea saman

The Propagation of Slow Wave Potentials in Pea Epicotyls

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