Water Movement Through Plant Roots

Landsberg, J. J.; Fowkes, Neville

doi:10.1093/oxfordjournals.aob.a085488

Cited by 234 publications

(193 citation statements)

References 15 publications

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“…R A and R L in the minor veins in Fig. 5; for the same principle applied to the root system, see Landsberg and Fowkes, 1978). Though the resistance of each radial leak may be large, the large number of leaks in parallel across the entire minor vein system leads to a relatively low overall integrated resistance.…”

Section: Temperature Responsesmentioning

confidence: 99%

Hydraulic Analysis of Water Flow through Leaves of Sugar Maple and Red Oak

2004

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Leaves constitute a substantial fraction of the total resistance to water flow through plants. A key question is how hydraulic resistance within the leaf is distributed among petiole, major veins, minor veins, and the pathways downstream of the veins. We partitioned the leaf hydraulic resistance (R leaf ) for sugar maple (Acer saccharum) and red oak (Quercus rubra) by measuring the resistance to water flow through leaves before and after cutting specific vein orders. Simulations using an electronic circuit analog with resistors arranged in a hierarchical reticulate network justified the partitioning of total R leaf into component additive resistances. On average 64% and 74% of the R leaf was situated within the leaf xylem for sugar maple and red oak, respectively. Substantial resistance-32% and 49%-was in the minor venation, 18% and 21% in the major venation, and 14% and 4% in the petiole. The large number of parallel paths (i.e. a large transfer surface) for water leaving the minor veins through the bundle sheath and out of the leaf resulted in the pathways outside the venation comprising only 36% and 26% of R leaf . Changing leaf temperature during measurement of R leaf for intact leaves resulted in a temperature response beyond that expected from changes in viscosity. The extra response was not found for leaves with veins cut, indicating that water crosses cell membranes after it leaves the xylem. The large proportion of resistance in the venation can explain why stomata respond to leaf xylem damage and cavitation. The hydraulic importance of the leaf vein system suggests that the diversity of vein system architectures observed in angiosperms may reflect variation in whole-leaf hydraulic capacity.Water flow through the leaf is one of the most important but least understood components of the whole-plant hydraulic system. The leaf hydraulic resistance (R leaf ) constitutes a significant hydraulic bottleneck, correlates with leaf structure, and apparently constrains gas exchange (Tyree and Zimmermann, 2002;Sack et al., 2003b;Sack and Tyree, 2004). R leaf is an aggregate measure; once past the petiole, water flows through a reticulate network of veins, across the bundle sheath cells, and through or around mesophyll cells before evaporation and diffusion from the stomata (Esau, 1965). Recent work has focused primarily on measurement of R leaf and its functional correlates. Few studies have attempted to determine quantitatively how the various components of the water flow pathway through the leaf contribute to its total resistance.Partitioning of R leaf is a crucial step for understanding leaf hydraulic design. Cavitation in the leaf vein xylem can substantially increase R leaf , as can physical damage to major veins; both drive reductions of leaf water potential and gas exchange Nardini et al., 2001Cochard et al., 2002;Huve et al., 2002;Sack et al., 2003a). These observations suggest that a large proportion of R leaf is situated in the veins. However, a number of studies have reported that most of the leaf resista...

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Section: Temperature Responsesmentioning

confidence: 99%

Hydraulic Analysis of Water Flow through Leaves of Sugar Maple and Red Oak

2004

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“…One of the first papers to propose this model as a description for root internal pressure variations along the root was Landsberg and Fowkes [73].…”

Section: Conservation Of Water Inside the Rootmentioning

confidence: 99%

A mathematical model of plant nutrient uptake

Koebernick¹,

Fowler²,

Darrah

2001

Journal of Mathematical Biology

107

159

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This thesis deals with the mathematical modelling of nutrient uptake by plant roots. It starts with the Nye-Tinker-Barber model for nutrient uptake by a single bare cylindrical root. The model is treated using matched asymptotic expansion and an analytic formula for the rate of nutrient uptake is derived for the first time. The basic model is then extended to include root hairs and mycorrhizae, which have been found experimentally to be very important for the uptake of immobile nutrients. Again, analytic expressions for nutrient uptake are derived. The simplicity and clarity of the analytical formulae for the solution of the single root models allows the extension of these models to more realistic branched roots. These models clearly show that the "volume averaging of branching structure" technique commonly used to extend the Nye-Tinker-Barber with experiments can lead to large errors. The same models also indicate that in the absence of large-scale water movement, due to rainfall, fertiliser fails to penetrate into the soil. This motivates us to build a model for water movement and uptake by branched root structures. This model considers the simultaneous flow of water in the soil, uptake by the roots, and flow within the root branching network to the stems of the plant. The water uptake model shows that the water saturation can develop pseudo-steadystate wet and dry zones in the rooting region of the soil. The dry zone is shown to stop the movement of nutrient from the top of the soil to the groundwater. Finally we present a model for the simultaneous movement and uptake of both nutrients and water. This is discussed as a new tool for interpreting available experimental results and designing future experiments. The parallels between evolution and mathematical optimisation are also discussed.

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“…The flow of water through the plant tissues is governed primarily by di↵erences in pressure and hence mainly follows the passive apoplasmic pathway through the cortex tissue (Steudle & Peterson, 1998). Following the approach of Steudle & Peterson (1998), Molz (1981), and Landsberg & Fowkes (1978) we treat the variety of tissues as a composite membrane and describe the radial flows (m s 1 ) aŝ…”

Section: Water Transport In the Xylemmentioning

confidence: 99%

“…Two boundary conditions are required to solve the model and we follow a similar approach to that of Landsberg & Fowkes (1978). At the tip of the xylem in the root zone we prescribe zero flux of water as we assume that the xylem terminus in the roots is axially impermeable to water.…”

Section: Water Transport In the Xylemmentioning

confidence: 99%

A Mathematical Model of Water and Nutrient Transport in Xylem Vessels of a Wheat Plant

et al. 2014

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At a time of increasing global demand for food, dwindling land and resources, and escalating pressures from climate change, the farming industry is undergoing financial strain, with a need to improve e ciency and crop yields. In order to improve e ciencies in farming, and in fertiliser usage in particular, understanding must be gained of the fertiliser-to-crop-yield pathway. We model one aspect of this pathway; the transport of nutrients within the vascular tissues of a crop plant from roots to leaves. We present a mathematical model of the transport of nutrients within the xylem vessels in response to the evapotranspiration of water. We determine 7 di↵erent classes of flow, including positive unidirectional flow, which is optimal for nutrient transport from the roots to the leaves; and root multidirectional flow, which is similar to the hydraulic lift process observed in plants. We also investigate the e↵ect of di↵usion on nutrient transport and find that di↵usion can be significant at the vessel termini especially if there is an axial e✏ux of nutrient, and at night when transpiration is minimal. Models such as these can then be coupled to whole-plant models to be used for optimisation of nutrient delivery scenarios.

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Water Movement Through Plant Roots

Cited by 234 publications

References 15 publications

Hydraulic Analysis of Water Flow through Leaves of Sugar Maple and Red Oak

Hydraulic Analysis of Water Flow through Leaves of Sugar Maple and Red Oak

A mathematical model of plant nutrient uptake

A Mathematical Model of Water and Nutrient Transport in Xylem Vessels of a Wheat Plant

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