Root-Pressure Exudation in Woody Plants

O’Leary, James W.

doi:10.1086/336303

Cited by 29 publications

(6 citation statements)

References 15 publications

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“…Many experiments have been carried out with excised roots or root systems, using applied pressure or suction to simulate the naturally occurring difference in pressure. Examples of this approach are given in papers by Mees & Weatherley (1957), Jackson & Weatherley (19620,6), Lopushinsky (1964), O'Leary (1965, Perry & Greenway (1973), Parsons & Kramer (1974) and Nulson & Thurtell (1978.…”

Section: ) External Concentration and Exudationmentioning

confidence: 99%

Transport across plant roots

Pitman

1982

Quart. Rev. Biophys.

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The plant root is a complex system that has evolved under the constraints of a number of functions. It is a pressure-probe that can penetrate the soil; it is a scavenger of nutrients that may be either tightly bound to soil particles or in low concentrations in the soil solution; it is an absorber of water from the soil. The tip of the root contains the region of dividing cells from which the root is formed, and is pushed through the soil by the extension of these cells some 10–20 times as they develop and differentiate.

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Section: ) External Concentration and Exudationmentioning

confidence: 99%

Transport across plant roots

Pitman

1982

Quart. Rev. Biophys.

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“…Although the movement of water through a plant is generally driven by a free energy gradient, resulting in the water column being under 'tension', positive pressure in the root system has been well documented to occur in a range of species, and is often cited in regards to monocotyledons (Fisher et al, 1997;Enns et al, 2000;Cao et al, 2012a;Gleason et al, 2017), but also in dicotyledon trees (O'Leary, 1965;Hacke & Sauter, 1996;Fisher et al, 1997), lianas (O'Leary, 1965;Fisher et al, 1997;Tibbetts and Ewers, 2000;Clearwater et al, 2007), and herbaceous species (Vaadia, 1960;Fisher et al, 1997;Stiller et al, 2003;De Swaef et al, 2013). Although the generating mechanism is yet to be identified (Pickard, 2003;Wegner, 2014), pressures range from ca 2 to 160 kPa and are known to decrease precipitously with increasing canopy transpiration and decreasing soil water potential (Fisher et al, 1997;Gleason et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Loss and recovery of leaf hydraulic conductance: Root pressure, embolism, and extra-xylary resistance

Ocheltree

Gleason²,

Cao³

et al. 2020

JPH

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Vascular networks in plant leaves must provide for the safe and efficient transport of water, nutrients, and energy; however, the conditions whereby these networks lose and regain conductive capacity are still poorly understood. We measured the loss and recovery of leaf hydraulic conductance (Kleaf) in a tropical monocotyledon (Bambusa vulgaris) and dicotyledon species (Bauhinia blakeana) using Rehydration Kinetics Method (RKM) as well as a recently developed optical method. We found that both species lost ca 88% of their maximal Kleaf (measured by RKM) before any embolization was detected in their conductive elements (via optical observation). This suggests that the majority of loss in Kleaf, as measured with RKM, was associated with resistances other than embolization. Furthermore, embolism in B. vulgaris, a species known to generate root pressure, was reversed when rehydrated under positive pressure (120 kPa), but not under atmospheric pressure. In contrast, embolism was not reversed in B. blakeana under either elevated or atmospheric pressure. However, reductions in Kleaf that was not associated with embolization was recovered by this species when rehydrated under atmospheric conditions, whereas B. vulgaris did not exhibit any recovery under the same conditions. We suggest that root pressure is an adaptive mechanism allowing for the reversal of embolism and the recovery of extraxylary conductance. The absence of embolism reversal in B. blakeana suggests that embolization may be permanent without neutral or positive xylem pressure, but that the recovery of extraxylary conductance can be regained routinely in this species in the absence of root pressure.

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“…Most workers have used detopped root systems to measure hydraulic root resistance. Four general methods have been reported: (a) application of hydrostatic pressure to a solution bathing the roots (Mees and Weatherley 1957a,b, ' Lopushinsky 1964, O'Leary 1965, Parson and Kramer 1974; (b) application of suction to the cut stump of the root system (Shirazi et at. 1975); (c) exudation measurements in the cut stump (Hay and Anderson 1972); and (d) changes in the osmotic concentration of the external solution in exudating root systems (solution-change method; Arisz et al 1951, Newman 1973.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Resistance of Rough Lemon Roots

Ramos

Kaufmann

1979

Physiologia Plantarum

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A pressure chamber technique was used to estimate hydraulic root resistance in rough lemon (Citrus jambhiri Lush.) seedlings. The effect of previous water stress on hydraulic root resistance was evaluated. A factorial 3 × 3 design with four replications was established with potted rough lemon seedlings in a growth chamber. Three water‐stress treatments were applied by watering at intervals of 1, 2 and 3 days, and root resistance measurements were made after 6, 12 and 18 days of treatment. Plants that had experienced mild and severe water stress (irrigation interval of 2 and 3 days, respectively) had higher hydraulic root resistances after several drying cycles than those plants irrigated daily. Additional cycles had no significant effect. The increase in root resistance was not due to decreased root growth but apparently to changes in the permeability of the root cell membranes or to increased suberin deposition in the cell walls of the cortical cells. In a short‐term experiment (1 h), temperature strongly affected water flow through rough lemon roots in the range 5 to 35°C. Temperature influenced root membrane permeability, since reduced blow could not be explained by changes in water viscosity.

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Root-Pressure Exudation in Woody Plants

Cited by 29 publications

References 15 publications

Transport across plant roots

Transport across plant roots

Loss and recovery of leaf hydraulic conductance: Root pressure, embolism, and extra-xylary resistance

Hydraulic Resistance of Rough Lemon Roots

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