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Lateral root

Lateral roots are post-embryonically formed secondary roots that originate from differentiated pericycle cells adjacent to the xylem poles in the primary root of vascular plants, serving as the primary building blocks of the root system by dramatically expanding its surface area to enhance water and nutrient uptake, anchorage, and overall plant adaptation to environmental conditions.^[1] In a single rye plant, for instance, the root system can produce over 13 million lateral roots within four months, underscoring their role in resource acquisition.^[1] Unlike the embryonic primary root, lateral roots develop continuously throughout the plant's life in response to internal and external cues, allowing dynamic remodeling of root architecture.^[2] The development of lateral roots proceeds through distinct stages: pre-patterning in the basal meristem, where auxin signaling primes pericycle cells; initiation via asymmetric anticlinal divisions of founder cells to form stage I primordia; outgrowth, involving periclinal divisions that shape a dome-like lateral root primordium (LRP); and emergence, where the LRP penetrates overlying tissues through cell separation and remodeling.^[3] This process, best studied in the model plant Arabidopsis thaliana, typically spans 1.6 to 3.6 days from initiation to emergence, depending on species and conditions.^[1] During morphogenesis, pericycle-derived cells acquire specific identities—such as stele, endodermis, and epidermis—while establishing a new stem cell niche, with contributions from surrounding parent root layers like the endodermis and cortex.^[1] Lateral root formation is tightly regulated by hormonal signals, particularly auxin, which acts as a central coordinator through receptors like TIR1 and transcription factors such as ARF7 and ARF19 to trigger founder cell specification and primordium patterning.^[3] Cytokinins and other hormones modulate this process, while genetic factors including LBD16/ASL18 and PUCHI ensure proper cell division and outgrowth.^[3] Environmental factors, such as nutrient availability and mechanical stimuli, further influence initiation sites and density, enabling plants to optimize root branching for survival in heterogeneous soils.^[2] Understanding these mechanisms holds promise for engineering improved root systems in crops to boost yield under stress.^[3]

Overview and Importance

Definition and Characteristics

Lateral roots are adventitious roots that branch laterally from the pericycle of the primary or seminal root axis in vascular plants, serving as the primary means of post-embryonic root system expansion.^[4] They originate endogenously within the parent root, distinguishing them from the primary root, which forms embryonically from the radicle during seed development.^[1] In contrast to other adventitious roots that arise from non-root tissues such as stems or leaves, lateral roots are specifically derived from root pericycle cells opposite the xylem poles.^[5] Key characteristics of lateral roots include their typically thinner diameter and shorter length compared to the primary root, enabling extensive proliferation for enhanced soil exploration.^[6] They exhibit a hierarchical branching structure, with first-order lateral roots emerging directly from the primary root, second-order roots from first-order laterals, and higher orders continuing this pattern to form complex networks.^[1] In many species, lateral root initiation follows an acropetal pattern, progressing from the basal (older) to apical (younger) regions of the parent root.^[7] Basic histological features of lateral roots mirror those of primary roots but on a smaller scale, including a protective root cap at the apex, an apical meristem with a quiescent center that drives indeterminate growth, and direct vascular connections to the parent root's stele via cambial derivatives.^[4] These elements ensure continuity of nutrient and water transport while allowing the lateral root to establish its own independent axis.^[5]

Role in Plant Root System

Lateral roots play a pivotal role in shaping the root system architecture (RSA) of plants by branching from the primary root, thereby dramatically increasing the overall surface area available for water and nutrient absorption, enhancing anchorage in the soil, and facilitating the exploration of larger soil volumes. This branching enables the root system to form complex networks that adapt to varying soil conditions, with lateral roots often constituting the majority of the total root length in mature plants, allowing for efficient resource acquisition and mechanical stability. For instance, in the model plant Arabidopsis thaliana, lateral roots account for the bulk of the root system's length, underscoring their dominance in RSA formation.^[8] The adaptive advantages of lateral roots are particularly evident in heterogeneous soil environments, where they enable targeted foraging for nutrients such as nitrate by proliferating preferentially in nutrient-rich patches, optimizing uptake efficiency while minimizing energy expenditure on unproductive areas.^[9] Additionally, lateral roots facilitate symbiotic relationships with soil microbes, including arbuscular mycorrhizal fungi, which colonize root surfaces to enhance phosphorus and nitrogen acquisition in exchange for plant-derived carbohydrates, thereby boosting overall plant fitness.^[10] In response to abiotic stresses like drought and salinity, lateral roots contribute to tolerance by allowing continued growth and exploration even under adverse conditions; for example, young lateral roots in Arabidopsis exhibit greater resilience to lethal salinity levels compared to the primary root, preserving the root system's functionality.^[11] Evolutionarily, the formation and function of lateral roots are highly conserved across vascular plants, appearing in angiosperms, gymnosperms, and certain ferns, where they consistently support RSA plasticity and environmental adaptation through similar developmental mechanisms involving pericycle or endodermal founder cells. This conservation highlights lateral roots' ancient origin in land plant evolution, predating the diversification of seed plants and enabling widespread success in diverse terrestrial habitats.^[12]

Morphology and Anatomy

External Structure

Lateral roots emerge endogenously from the pericycle layer of the parent root, specifically at discrete sites adjacent to the protoxylem poles, allowing them to penetrate outward through the cortical and epidermal tissues.^[13] This emergence occurs at an angle of approximately 90° relative to the parent root.^[14] Upon breaking through the epidermis, the young lateral root tip orients itself to explore new soil volumes while maintaining a connection to the parent root's vascular system. The external surface of lateral roots features numerous root hairs, which emerge from epidermal cells shortly after emergence and extend the absorptive capacity by increasing surface area.^[15] Unlike stems, lateral roots lack lenticels, relying instead on diffusion through their thin epidermis for gas exchange, and their diameter typically ranges from 0.1 to 1 mm, varying with root order and species—finer for higher-order laterals and coarser for primary branches.^[16] These surface characteristics contribute to the root's compact, streamlined form suited for subsurface navigation. Branching patterns among lateral roots differ based on growth habit: determinate types exhibit finite elongation without further branching, ceasing growth after reaching a set length, whereas indeterminate types continue apical meristem activity, producing successive orders of laterals.^[17] In cereals like maize and pearl millet, lateral roots often develop in clustered formations, where multiple roots emerge in close proximity along the parent axis, enhancing localized soil exploitation.^[18] Observable variations in lateral root external structure align with overall root system architecture; in taproot systems typical of dicots (e.g., Arabidopsis), laterals are generally shorter (often <10 cm) and sparser, supporting deep anchorage with limited horizontal spread, while fibrous systems in monocots (e.g., rice) produce longer, more extensive lateral networks that form dense mats near the soil surface.^[19] This external configuration briefly interfaces with the parent root's internal vascular tissues via vascular connections at the emergence point.

Internal Organization

Lateral roots exhibit a histological organization analogous to that of primary roots, consisting of concentric tissue layers that facilitate protection, transport, and selective absorption. The outermost layer is the epidermis, a single cell layer that provides a protective barrier and facilitates water and nutrient uptake through root hairs in some regions.^[20] Beneath the epidermis lies the cortex, composed of multiple layers of parenchyma cells that store reserves and contribute to radial transport.^[20] The endodermis, a uniseriate layer internal to the cortex, features thickened cell walls and serves as a regulatory barrier.^[21] Adjacent to the endodermis is the pericycle, a layer of meristematic cells that encases the central stele and acts as the primary site for lateral root initiation.^[20] The central stele contains the vascular tissues, including xylem for water conduction and phloem for nutrient distribution, organized in a diarch or polyarch pattern depending on the species.^[22] Vascular continuity between the lateral root and the parent root is maintained through a diagonal connection of the lateral root stele to the xylem poles of the parent root, forming a xylem bridge that ensures efficient flow of water and solutes.^[23] This connection, established via coordinated procambial and pericycle contributions, preserves the integrity of the plant's vascular network.^[13] At the apex, the lateral root meristem includes a quiescent center (QC), a small group of slowly dividing cells surrounded by initial cells that give rise to the various tissue layers, mirroring the structure of primary root meristems but typically on a reduced scale.^[24] Specialized features enhance the functionality of these tissues; notably, the Casparian strip in the endodermal cell walls forms a lignified, hydrophobic impregnation that blocks apoplastic pathways, promoting selective permeability and forcing solutes through symplastic routes.^[21] In some short lateral roots, particularly in species like pines, the root cap may be reduced or absent, altering protection of the meristem tip compared to longer laterals.^[25]

Development and Formation

Initiation Sites and Stages

Lateral roots primarily initiate from pericycle cells positioned adjacent to the xylem poles within the primary root vasculature. These xylem pole pericycle (XPP) cells, which lie opposite the phloem poles, become competent for initiation shortly after seed germination, serving as the exclusive sites for lateral root primordia formation in Arabidopsis thaliana.^[3]^[26] The initiation process unfolds in sequential stages observable through histological analysis. It begins with asymmetric anticlinal divisions in the specified pericycle founder cells, producing stage I primordia as short files of enlarged cells aligned with the root axis. This is followed by periclinal divisions that establish the founding primordium, typically consisting of 4-8 cells arranged in two cell layers (stage II). Subsequent rounds of anticlinal and periclinal divisions organize the structure into a dome-shaped stage III primordium, culminating in stage IV where the primordium emerges laterally by degrading and displacing the overlying cortex and epidermis.^[2] In Arabidopsis, the first lateral root primordia typically initiate around 1-2 days post-germination within the root differentiation zone, a timing closely tied to the primary root's elongation rate, which determines the available pericycle length for potential initiation sites.^[27]^[7] Lateral root primordia are patterned along the primary root in a regular, acropetal manner with alternating left-right orientation relative to the xylem axis, ensuring even distribution. This spacing arises from inhibitory fields projected by each developing primordium, which suppress nearby pericycle cells from initiating new primordia and thereby avert overcrowding.^[28]^[29] These initiation stages are triggered by localized auxin gradients that specify and synchronize founder cell activation.^[30]

Growth and Elongation Processes

Following emergence from the parent root, lateral root elongation occurs primarily in the sub-apical elongation zone, where cells undergo rapid anisotropic expansion to increase root length. This process is driven by turgor pressure generated within the cells, which exerts mechanical force against the cell walls, combined with localized loosening of the cell wall matrix to allow irreversible expansion. In Arabidopsis thaliana lateral roots, cell expansion in this zone is regulated by mechanisms such as RAB-A5c-mediated trafficking to cell edges, which modulates wall stiffness independently of cortical microtubule orientation, ensuring directional growth along the root axis. Apoplastic acidification, often triggered by auxin signaling, further activates expansins and other wall-loosening enzymes, reducing pH to below 5 and facilitating turgor-driven elongation in the sub-apical region.^[31]^[32] Lateral root systems exhibit a hierarchical branching pattern, where higher-order lateral roots (secondaries, tertiaries, etc.) emerge from the pericycle of parent lateral roots, creating a fractal-like architecture that enhances soil exploration efficiency. This hierarchy establishes dominance, with daughter laterals typically finer in diameter (e.g., slopes of 0.062–0.39 in diameter ratios between laterals and mothers) and shorter than their progenitors, observed across both monocotyledonous and dicotyledonous species. The resulting network displays fractal properties along axes of fineness-density and heterorhizy-dominance, allowing adaptive scaling of root proliferation without excessive biomass investment.^[33] Growth rates of elongating lateral roots vary by species, developmental stage, and environmental conditions, typically ranging from 1 to 3 mm per day in model systems like Arabidopsis thaliana under standard laboratory conditions. Rates accelerate with factors like nutrient availability and moisture. Recent studies (as of 2025) highlight roles for peptide signaling and nutrient-specific transcriptomic responses in modulating elongation rates and plasticity.^[15]^[34] Lateral root growth terminates through either determinate or indeterminate patterns, depending on species and conditions. In determinate types, such as short lateral rootlets in proteoid roots of Lupinus albus or certain Cactaceae species, the apical meristem exhausts after 3–6 days of growth, leading to full differentiation of meristematic cells into root hairs and cessation of elongation at lengths of approximately 5 mm. Indeterminate growth, common in Arabidopsis thaliana lateral roots, maintains an active quiescent center and stem cell niche, allowing continuous meristem renewal and prolonged elongation unless disrupted by stress or hormonal shifts. This dichotomy enables adaptive root system plasticity, with determinate laterals prioritizing rapid, finite exploration.^[35]^[36]

Molecular Regulation

Signaling Pathways

The signaling pathways regulating lateral root formation in Arabidopsis thaliana center on the GRAS family transcription factors SHORT-ROOT (SHR) and SCARECROW (SCR), which specify pericycle competence for initiation. SHR, expressed in the stele, encodes a mobile protein that enters adjacent cell types including the endodermis and quiescent center (QC), where it directly activates SCR expression to promote asymmetric pericycle divisions necessary for primordium formation. This SHR-SCR module establishes radial patterning and maintains the stem cell niche, with shr mutants showing fewer than 40% of seedlings developing lateral roots and an over 3-fold reduction in emerged lateral roots, along with frequent patterning defects in emerged roots, such as disorganized cell layers. SCR further reinforces the pathway by interacting with SHR to regulate downstream targets like cell cycle genes, ensuring precise founder cell specification in the pericycle.^[37] PLETHORA (PLT) genes, belonging to the AP2/ERF transcription factor family, function downstream to maintain the meristem in developing lateral roots. PLT3, PLT5, and PLT7 initiate formative periclinal divisions during the transition from stage I to II primordia, while PLT1, PLT2, and PLT4 sustain stem cell proliferation and identity by activating QC-specific markers like WOX5 and coordinating tissue organization. In plt3 plt5 plt7 triple mutants, approximately 60% of stage II primordia and 50% of stage III primordia lack proper divisions, resulting in arrested meristem development and short or absent lateral roots. These PLTs form a transcriptional network that redeploys SHR and SCR for radial patterning in nascent organs, with any single PLT capable of partially rescuing meristem function when ectopically expressed.^[38] Transcriptional networks involving NAC domain proteins integrate developmental cues to fine-tune lateral root formation, with NAC1 exemplifying this role by promoting pericycle cell cycle entry and primordium outgrowth through regulation of downstream targets. NAC1 expression in founder cells activates genes essential for division asymmetry, and nac1 loss-of-function mutants show reduced lateral root numbers, highlighting its integration into broader cascades. Feedback loops within these networks autoregulate primordia spacing and patterning.^[39] Genetic mutants such as solitary root1 (slr-1) illustrate the indispensability of these interconnected pathways, as slr-1 disrupts pericycle activation and blocks all lateral root initiation at the pre-division stage, revealing essential checkpoints in the SHR-SCR-PLT cascade for founder cell fate commitment.^[40]

Hormone Involvement

Auxin serves as the primary hormone regulating lateral root initiation and development, acting through its perception by the TIR1/AUXIN SIGNALING F-BOX (TIR1/AFB) receptor complex, which facilitates the ubiquitination and degradation of AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) repressor proteins.^[41] This degradation relieves repression on AUXIN RESPONSE FACTOR (ARF) transcription factors, such as ARF7 and ARF19, enabling the activation of downstream genes essential for lateral root primordia specification and outgrowth in the pericycle layer. Local auxin maxima, often generated by polar transport, are critical for priming pericycle cells and coordinating the oscillatory gene expression patterns that precede primordia formation.^[42] In contrast, cytokinin exerts an inhibitory effect on lateral root development, counterbalancing auxin's promotive role to prevent excessive branching and maintain root system architecture. Cytokinin signaling, mediated through histidine kinases and type-B ARABIDOPSIS RESPONSE REGULATOR (ARR) transcription factors, upregulates type-A ARRs like ARR5, ARR6, and ARR7, which act as negative feedback regulators to suppress auxin-responsive genes and limit primordia initiation.^[43] This inhibition is particularly evident in the root elongation zone, where elevated cytokinin levels reduce the number of emergent lateral roots, ensuring resource allocation to the primary root under optimal conditions.^[44] Abscisic acid (ABA) primarily inhibits lateral root growth in response to abiotic stresses such as drought or salinity, integrating environmental cues with developmental control. Under stress, ABA activates PYRABACTIN RESISTANCE1/PYL/RCAR (PYL/RCAR) receptors, which inhibit protein phosphatase 2Cs, leading to activation of ABA-responsive factors like ABI3 and ERF1 that mediate crosstalk with auxin signaling to repress lateral root emergence, often by altering auxin transport and distribution.^[45] Strigolactones, another class of hormones, fine-tune lateral root density by suppressing initiation sites, particularly under nutrient-limited conditions like low phosphate, where they reduce lateral root number while enhancing root hair elongation to optimize foraging efficiency.^[46] Hormonal crosstalk, especially between auxin and cytokinin, finely tunes lateral root primordia fate through their relative concentrations, with high auxin-to-cytokinin ratios favoring initiation and outgrowth while balanced or cytokinin-dominant ratios promote quiescence or abortion.^[42] This antagonistic interaction occurs at multiple levels, including shared regulation of transport carriers like PIN-FORMED (PIN) proteins, and influences the spatial patterning of root branching to adapt to soil heterogeneity.^[47] ABA and strigolactones further modulate this balance under stress or nutrient scarcity, integrating into the auxin-cytokinin network to prioritize survival over proliferation.

Auxin Transport Mechanisms

PIN Protein Functions

The PIN-FORMED (PIN) proteins constitute a family of eight members in Arabidopsis thaliana (PIN1 through PIN8), which function as secondary active transporters mediating the efflux of the plant hormone auxin (indole-3-acetic acid, IAA) across the plasma membrane.^[48] Among these, the long forms PIN1, PIN3, PIN4, and PIN7 are particularly crucial for lateral root development, as they facilitate the directional transport of auxin to establish necessary concentration gradients during primordia formation and outgrowth.^[49] These proteins operate via an elevator mechanism, exporting auxin anions out of cells in a proton-gradient-dependent manner, without direct ATP hydrolysis, thereby enabling energy-efficient polar auxin flow.^[50] In the context of lateral roots, PIN-mediated efflux creates asymmetric auxin distributions that specify pericycle founder cells and promote subsequent developmental stages.^[51] PIN proteins exhibit polarized localization on the plasma membrane, which is essential for directing auxin streams in root tissues. In vascular cells, PIN1, PIN3, PIN4, and PIN7 are predominantly localized to the basal membrane, facilitating acropetal auxin transport toward the root tip and supporting overall root architecture.^[52] During lateral root primordia specification, however, these proteins relocalize laterally in pericycle cells adjacent to protoxylem poles, promoting auxin convergence and the activation of founder cell identity; this dynamic repositioning is auxin-dependent and coordinates the oscillatory signaling that times initiation events.^[51] Such localization patterns ensure that auxin maxima form at discrete sites, preventing uniform outgrowth and enabling patterned branching.^[49] Genetic studies underscore the roles of these PIN proteins through loss-of-function mutants. The pin1 mutant exhibits reduced lateral root branching, with normal initiation of primordia but fewer emergent and mature roots due to impaired auxin transport during outgrowth.^[53] This phenotype highlights functional redundancy among PIN family members, as pin1 defects are exacerbated in combinations with mutations in PIN3, PIN4, or PIN7, such as the pin3 pin4 pin7 triple mutant, which shows severe reductions in lateral root number and altered primordia progression owing to disrupted auxin redistribution. These observations demonstrate how overlapping PIN functions ensure robust lateral root development under varying conditions.^[49]

Polarity and Gradient Formation

The establishment of auxin gradients in the root pericycle is driven by a positive feedback loop between auxin accumulation and the polar localization of PIN-FORMED (PIN) efflux carriers. High auxin levels at potential initiation sites promote the basally directed targeting of PIN proteins, which in turn enhances auxin efflux from neighboring cells, reinforcing local maxima in the pericycle and restricting diffusion to create discrete hotspots for lateral root founder cell specification.^[54]^[55] Polarity of PIN proteins is dynamically maintained through endosomal recycling pathways, where PINs are internalized via clathrin-mediated endocytosis and recycled back to the plasma membrane in a polarized manner to sustain directional auxin transport. This recycling is tightly regulated by phosphorylation events, particularly by AGC kinases such as PID (PINOID), which phosphorylate specific serine residues on PINs to favor apical or basal localization depending on the cellular context, thereby fine-tuning gradient directionality during lateral root positioning.^[56]^[57] Spatial patterning of lateral root initiation arises from oscillatory auxin signaling waves that propagate from the root tip, priming pericycle cells at regular intervals of approximately 5-10 mm along the primary root axis. These oscillations, driven by an auxin-regulable genetic circuit involving feedback between auxin response factors and transport regulators, create transient peaks in auxin responsiveness that pre-select founder sites before full primordia formation.^[58]^[59]^[7] Mathematical models, particularly reaction-diffusion frameworks incorporating auxin transport feedback, demonstrate how these gradients lead to threshold-dependent primordia formation by simulating the emergence of stable auxin maxima only when local concentrations exceed a critical level, preventing overlapping initiations and ensuring spaced patterning.^[60]^[61]

Functions and Adaptations

Nutrient and Water Uptake

Lateral roots play a crucial role in enhancing nutrient and water uptake by expanding the root system's absorptive capacity through their proliferation and association with root hairs. These fine structures, often covered by dense root hairs, significantly increase the overall surface area available for absorption, enabling more efficient exploitation of soil resources compared to the primary root alone. In many plant species, root hairs on lateral roots can boost the absorptive surface area by 10- to 100-fold relative to hairless primary roots, facilitating greater contact with soil particles and depletion zones around the root surface.^[62]^[63] The endodermal layer in lateral roots, featuring the Casparian strip as an apoplastic barrier, directs ions into the symplast, promoting selective uptake through specialized transporters. This barrier prevents unregulated passive diffusion, allowing plants to control the influx of essential nutrients like nitrate via high-affinity transporters such as those in the NRT2 family, which are expressed in the root cortex and epidermis. For instance, NRT2.1 facilitates nitrate acquisition under low soil concentrations, optimizing resource allocation in heterogeneous environments.^[64]^[65] Water uptake in lateral roots is supported by their higher hydraulic conductivity, particularly in unsuberized fine laterals, where aquaporins—plasma membrane intrinsic proteins—form water channels that enhance radial flow across cell membranes. These proteins contribute to rapid adjustments in water permeability, with peak expression often near root tips, enabling efficient hydration even in drier soil layers. Fine lateral roots exhibit elevated hydraulic conductance compared to thicker primary roots, aiding overall plant water balance.^[66]^[67] By branching into soil microsites, lateral roots enable targeted foraging for patchy nutrients, such as localized phosphorus or nitrogen deposits, through proliferation and elongation in resource-rich zones. This architectural adaptation allows access to heterogeneous soil patches that the primary root might overlook, improving acquisition efficiency without excessive energy investment in root growth.^[68]^[69]

Environmental Responses

Lateral roots demonstrate adaptive plasticity to nutrient deficiencies, particularly low phosphate availability, by increasing branching density to improve foraging in heterogeneous soils. In Arabidopsis, low phosphate conditions enhance auxin sensitivity in pericycle cells through upregulation of the TIR1 auxin receptor, accelerating lateral root primordia formation and emergence, which doubles the number of lateral roots compared to phosphate-sufficient conditions.^[70] This response is regulated downstream by auxin response factors ARF7 and ARF19, which directly activate the transcription factors LBD16 and LBD29 to promote lateral root initiation and development under nutrient stress.^[71] Under drought stress, lateral root elongation is inhibited to conserve resources and maintain a shallower root architecture for accessing residual surface water. Abscisic acid (ABA), which accumulates rapidly in roots during water deficit, mediates this inhibition by reducing cell expansion in emerging lateral roots, thereby limiting their depth penetration while favoring initiation near the soil surface.^[72] This ABA-dependent remodeling enhances plant survival by prioritizing water uptake from upper soil layers where moisture availability is higher during dry periods.^[73] Biotic interactions in the soil microbiome also influence lateral root development, often enhancing branching to facilitate symbiotic associations or evade pathogens. Arbuscular mycorrhizal fungi (AMF) stimulate lateral root formation in host plants such as tomato and rice by signaling through strigolactones and auxin pathways, increasing root branching by up to 30-50% to provide more entry points for fungal colonization and mutualistic nutrient exchange.^[74] Lateral roots exhibit high plasticity through tropic responses, such as hydrotropism, which directs their growth toward moisture gradients in the soil. In Arabidopsis, hydrotropism involves asymmetric distribution of cytokinins and ABA in the root tip, bending lateral roots toward higher water potential areas to optimize hydration without excessive energy expenditure.^[75] This adaptive mechanism allows plants to fine-tune root architecture for efficient water capture while minimizing growth in dry zones.^[76]

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Many aspects of root development are co-ordinated by subtle spatial differences in the concentrations of the phytohormones auxin and cytokinin. Events from the ...
[41]
Genome-wide comparative analysis of type-A Arabidopsis response ...
Jul 21, 2009 · A major function of type-A ARR proteins is to act as negative regulators of cytokinin signaling by repressing type-B ARRs via unknown mechanisms ...
[42]
Cytokinin response factors regulate PIN-FORMED auxin transporters
Nov 6, 2015 · Typically, an increase in cytokinin activity alters root growth and development: cytokinins restrict root elongation growth, cause shortening of ...
[43]
The ABA receptor PYL8 promotes lateral root growth by ... - PubMed
Jun 3, 2014 · The phytohormone abscisic acid (ABA) regulates plant growth, development, and abiotic stress responses. ABA signaling is mediated by a group ...
[44]
From lateral root density to nodule number, the strigolactone ...
We provide evidence that addition of the synthetic strigolactone analogue GR24 has an inhibitory effect on the lateral root density.
[45]
Hormone interactions during lateral root formation - PubMed
Recent studies have shown that the plant hormones, cytokinin and abscisic acid negatively regulate LR formation whereas brassinosteroids positively regulate LR ...
[46]
The PIN-FORMED (PIN) protein family of auxin transporters - PMC
The PIN-FORMED (PIN) proteins are secondary transporters acting in the efflux of the plant signal molecule auxin from cells.
[47]
PIN-Dependent Auxin Transport: Action, Regulation, and Evolution
In pin mutants, lateral roots are generated at lower frequency, progress more slowly through development, or cannot be formed at all, instead resulting in a ...
[48]
PIN structures shed light on their mechanism of auxin efflux
The atomic structures and associated activity assays reveal that PINs use an elevator mechanism to transport auxin anions out of the cell.
[49]
https://pmc.ncbi.nlm.nih.gov/articles/PMC4330589/
[50]
https://academic.oup.com/jxb/article/74/15/4377/7169301
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Mutations in Arabidopsis Multidrug Resistance-Like ABC ...
The pin1 mutant, presumably defective in root acropetal transport, initiates lateral root primordia but produces fewer mature lateral roots than the wild type ...
[52]
Canalization of auxin flow by Aux/IAA-ARF-dependent feedback ...
Our data suggest that auxin acts as polarizing cue, which links individual cell polarity with tissue and organ polarity through control of PIN polar targeting.
[53]
Auxin acts as a local morphogenetic trigger to specify lateral root ...
Here, we show that auxin and its local accumulation in root pericycle cells is a necessary and sufficient signal to respecify these cells into lateral root ...
[54]
PIN Auxin Carrier Polarity: Recycling, Clustering, Endocytosis
We show that polar-competent PIN transporters for the phytohormone auxin are delivered to the center of polar domains by super-polar recycling.
[55]
PID/WAG-mediated phosphorylation of the Arabidopsis PIN3 auxin ...
Jul 6, 2018 · PIN phosphorylation by the protein kinase PID has been implicated in both apical/basal PIN polarity and tropic responses. Here we have ...
[56]
An auxin-regulable oscillatory circuit drives the root clock ... - Science
Jan 1, 2021 · In Arabidopsis, the root clock regulates the spacing of lateral organs along the primary root through oscillating gene expression.
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Periodic Lateral Root Priming: What Makes It Tick? - PubMed
Feb 21, 2017 · This priming of lateral roots occurs rhythmically, involving temporal oscillations in auxin response in the root tip.
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The Role of Auxin Transport in Plant Patterning Mechanisms - PMC
Dec 16, 2008 · In plants, many patterning processes involve the phytohormone auxin, and controlling how it moves around plays a critical role in pattern formation.
[59]
Auxin transport‐feedback models of patterning in plants - 2009
Aug 5, 2009 · Here, we review simulation models of pattern formation that are based on the control of these transporters by auxin itself. In these transport- ...
[60]
Water Uptake and Transport in Vascular Plants - Nature
Fine roots can be covered by root hairs that significantly increase the absorptive surface area and improve contact between roots and the soil (Figure 2). Some ...
[61]
Root hairs increase rhizosphere extension and carbon input to soil
Dec 18, 2017 · Root hairs contribute between 70 and 90 % of the total root surface area and there is evidence that they improve nutrient acquisition (Bates ...
[62]
Transporters Involved in Root Nitrate Uptake and Sensing by ... - PMC
Four families of transporters participate in nitrate uptake, distribution or storage: NITRATE TRANSPORTER 2 (NRT2) transporters (Orsel et al., 2002; Krapp et al ...
[63]
Modeling Root Zone Effects on Preferred Pathways for the Passive ...
Jun 22, 2016 · The CS is a barrier that consists predominantly of lignin (Naseer et al., 2012) which blocks the passive uptake of ions (and possibly water) via ...Missing: NRT | Show results with:NRT
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Water Uptake along the Length of Grapevine Fine Roots
Low aquaporin expression and activity in suberized secondary growth portions of fine roots suggests a limited role in controlling water uptake in this region ...
[65]
Roles of Morphology, Anatomy, and Aquaporins in Determining ...
Anatomy played a major role in root hydraulics, influencing axial conductance (L ax) and the distribution of water uptake along the root, with a more localized ...
[66]
Root Nutrient Foraging - PMC - NIH
One reason for the formation of nutrient patches within the soil relates to the rather uneven distribution of organic matter (Van Noordwijk et al., 1993) and ...
[67]
Microprofiling of nitrogen patches in paddy soil - Nature
Jun 6, 2016 · When roots encounter a nutrient-rich zone or patch, they often proliferate within it, including increases in elongation of individual roots; ...
[68]
Phosphate Availability Alters Lateral Root Development in ...
Plants are endowed with nutrient sensing mechanisms that allow them to respond and adapt their growth and development to conditions of limited nutrient supply.Missing: LBD16 LBD29
[69]
The ARF7 and ARF19 Transcription Factors Positively Regulate ...
Under low-Pi conditions, the increase in lateral root formation in Arabidopsis is mediated by an increase in auxin sensitivity of root cells, a process in which ...
[70]
Low ABA concentration promotes root growth and hydrotropism ...
Mar 17, 2021 · The presence of low ABA concentration (0.1 micromolar), inhibiting PP2C activity via monomeric ABA receptors, enhances root apoplastic H + efflux and growth of ...
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Arbuscular mycorrhizal fungi induce lateral root development in ...
Oct 24, 2022 · Lateral root development in both monocotyledons and dicotyledons is enhanced in response to inoculation with arbuscular mycorrhizal (AM) fungi.
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A role for LATERAL ORGAN BOUNDARIES‐DOMAIN 16 during the ...
May 6, 2014 · We investigated the possibility that nematode secretions could trigger changes in pericycle cells by inducing the expression of LBD16.
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Molecular mechanisms mediating root hydrotropism - NIH
Dec 4, 2019 · Root hydrotropism is thought to facilitate plant adaptation to continuously changing water availability. Hydrotropism has not been as ...
[74]
The Optimal Lateral Root Branching Density for Maize Depends on ...
Significant genotypic variation in the density of lateral roots has been observed, ranging from no lateral roots to 41 roots cm−1 in maize (Table I; Trachsel et ...Missing: hydrotropism | Show results with:hydrotropism