How Do Real Roots Work? (Some New Views of Root Structure)

McCully, M. E.

doi:10.1104/pp.109.1.1

Cited by 126 publications

(53 citation statements)

References 16 publications

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“…1C) than EMX (approximately at 100 mm from the apical meristem, Fig. 1D) in agreement with McCully (1995). As shown in Figure 1H, in the more mature region of the root, where the xylem was well differentiated, high PAO enzymatic activity was evident in the vascular cylinder.…”

Section: Cell-and Tissue-specific Expression Of Pao In Maize Primary supporting

confidence: 74%

Perturbation of Polyamine Catabolism Can Strongly Affect Root Development and Xylem Differentiation

et al. 2011

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Spermidine (Spd) treatment inhibited root cell elongation, promoted deposition of phenolics in cell walls of rhizodermis, xylem elements, and vascular parenchyma, and resulted in a higher number of cells resting in G 1 and G 2 phases in the maize (Zea mays) primary root apex. Furthermore, Spd treatment induced nuclear condensation and DNA fragmentation as well as precocious differentiation and cell death in both early metaxylem and late metaxylem precursors. Treatment with either N-prenylagmatine, a selective inhibitor of polyamine oxidase (PAO) enzyme activity, or N,N 1 -dimethylthiourea, a hydrogen peroxide (H 2 O 2 ) scavenger, reverted Spd-induced autofluorescence intensification, DNA fragmentation, inhibition of root cell elongation, as well as reduction of percentage of nuclei in S phase. Transmission electron microscopy showed that N-prenylagmatine inhibited the differentiation of the secondary wall of early and late metaxylem elements, and xylem parenchymal cells. Moreover, although root growth and xylem differentiation in antisense PAO tobacco (Nicotiana tabacum) plants were unaltered, overexpression of maize PAO (SZmPAO) as well as down-regulation of the gene encoding S-adenosyl-L-methionine decarboxylase via RNAi in tobacco plants promoted vascular cell differentiation and induced programmed cell death in root cap cells. Furthermore, following Spd treatment in maize and ZmPAO overexpression in tobacco, the in vivo H 2 O 2 production was enhanced in xylem tissues. Overall, our results suggest that, after Spd supply or PAO overexpression, H 2 O 2 derived from polyamine catabolism behaves as a signal for secondary wall deposition and for induction of developmental programmed cell death.

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Section: Cell-and Tissue-specific Expression Of Pao In Maize Primary supporting

confidence: 74%

Perturbation of Polyamine Catabolism Can Strongly Affect Root Development and Xylem Differentiation

et al. 2011

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“…Although such processes have been studied to some extent, testing hypothesis 1 will require measuring root pressures for relevant species in natural settings in comparison to the strength of rocky material. Of course, laboratory experiments on root strength are poorly suited to real-world bedrock settings in terms of both quantifying stresses over daily or annual timescales and replicating the fracture mechanics that result in actual root-fissure configurations (Gill and Bolt, 1955;Eavis et al, 1969;Misra et al, 1986;McCully, 1995;Gregory, 2006). Thus new techniques are needed to measure external root pressures in situ.…”

Section: Building and Plumbing The Critical Zonementioning

confidence: 99%

Reviews and syntheses: on the roles trees play in building and plumbing the critical zone

et al. 2017

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Abstract. Trees, the most successful biological power plants on earth, build and plumb the critical zone (CZ) in ways that we do not yet understand. To encourage exploration of the character and implications of interactions between trees and soil in the CZ, we propose nine hypotheses that can be tested at diverse settings. The hypotheses are roughly divided into those about the architecture (building) and those about the water (plumbing) in the CZ, but the two functions are intertwined. Depending upon one's disciplinary background, many of the nine hypotheses listed below may appear obviously true or obviously false. (1) Tree roots can only physically penetrate and biogeochemically comminute the immobile substrate underlying mobile soil where that underlying substrate is fractured or pre-weathered. (2) In settings where the thickness of weathered material, H , is large, trees primarily shape the CZ through biogeochemical reactions within the rooting zone. (3) In forested uplands, the thickness of mobile soil, h, can evolve toward a steady state because of feedbacks related to root disruption and tree throw. (4) In settings where h H and the rates of uplift and erosion are low, the uptake of phosphorus into trees is buffered by the fine-grained fraction of the soil, and the ultimate source of this phosphorus is dust. (5) In settings of limited water availability, trees maintain the highest length density of functional roots at depths where water can be extracted over most of the growing season with the least amount of energy expenditure. (6) Trees grow the majority of their roots in the zone where the most growth-limiting resource is abundant, but they also grow roots at other depths to forage for other resources and to hydraulically redistribute those resources to depths where they can be taken up more efficiently. (7) Trees rely on matrix water in the unsaturated zone that at times may have anPublished by Copernicus Publications on behalf of the European Geosciences Union. 5116 S. L. Brantley et al.: Reviews and syntheses: on the roles trees play in building and plumbing the critical zone isotopic composition distinct from the gravity-drained water that transits from the hillslope to groundwater and streamflow. (8) Mycorrhizal fungi can use matrix water directly, but trees can only use this water by accessing it indirectly through the fungi. (9) Even trees growing well above the valley floor of a catchment can directly affect stream chemistry where changes in permeability near the rooting zone promote intermittent zones of water saturation and downslope flow of water to the stream. By testing these nine hypotheses, we will generate important new cross-disciplinary insights that advance CZ science.

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“…Agave deserti, was increased by mycorrhizal infection owing to higher radial conductivity in roots, which appeared to be related to enhanced nutritional status of the myeorrhizal host. Mycorrhizas can also affect the morphology of root systems (Sieverding, 1986;Kothari et al, 1990) and, since branch root junctions can facilitate radial transport of water (McCuUy, 1995), it is possible that higher specific water uptake in mycorrhizal plants might also be related to alterations in root morphology.…”

Section: Introductionmentioning

confidence: 99%

Water uptake by safflower and wheat roots infected with arbuscular mycorrhizal fungi

Bryla

Duniway

1997

New Phytologist

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SUMMARYThe objective of this study was to determine if infection by arbuscular mycorrhizal fungi alters water uptake by roots under well watered to severely droughted conditions. Safflower and wheat plants were grown with and without the mycorrhizal fungi, Glojnus etunicatuin or G. intraradices in nutrient-amended soil under environmentally controlled conditions to yield mycorrhizal and non-mycorrhizal plants with similar leaf areas, root length densities, d. wt, and adequate tissue phosphorus and nitrogen. Specific water uptake rates (cm'* of water cm ' root length d'') were estimated non-destructively at various depths in the soil from changes in the soil water content measured using a gamma attenuation method. When soil water was severely depleted, changes in soil water potentials were also measured with soil psychrometers. Roots from both plant species extracted water at the fastest rate from the upper soil layers when the soil water content was high, and later, extracted water primarily from deeper depths as water in the upper soil layers was depleted. Mycorrhizal infection did not affect the rates at which roots e.xtracted water from soil whether soil moisture conditions were at their wettest condition, at container capacity, or at the driest extreme when soil water potentials ranged from -1-5 to -2'0 MPa and the plants were completely wilted. Plant water relations were also largely unaffected by infection. Mycorrhiza! infection did not alter the ability of plants to extract water from soil even during extreme drought.

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How Do Real Roots Work? (Some New Views of Root Structure)

Cited by 126 publications

References 16 publications

Perturbation of Polyamine Catabolism Can Strongly Affect Root Development and Xylem Differentiation

Perturbation of Polyamine Catabolism Can Strongly Affect Root Development and Xylem Differentiation

Reviews and syntheses: on the roles trees play in building and plumbing the critical zone

Water uptake by safflower and wheat roots infected with arbuscular mycorrhizal fungi

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