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Kim M, Hyeon DY, Kim K, Hwang D, Lee Y. Phytohormonal regulation determines the organization pattern of shoot aerenchyma in greater duckweed (Spirodela polyrhiza). PLANT PHYSIOLOGY 2024; 195:2694-2711. [PMID: 38527800 PMCID: PMC11288743 DOI: 10.1093/plphys/kiae173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 02/13/2024] [Accepted: 02/19/2024] [Indexed: 03/27/2024]
Abstract
Airspace or aerenchyma is crucial for plant development and acclimation to stresses such as hypoxia, drought, and nutritional deficiency. Although ethylene-mediated signaling cascades are known to regulate aerenchyma formation in stems and roots under hypoxic conditions, the precise mechanisms remain unclear. Moreover, the cellular dynamics underlying airspace formation in shoots are poorly understood. We investigated the stage-dependent structural dynamics of shoot aerenchyma in greater duckweed (Spirodela polyrhiza), a fast-growing aquatic herb with well-developed aerenchyma in its floating fronds. Using X-ray micro-computed tomography and histological analysis, we showed that the spatial framework of aerenchyma is established before frond volume increases, driven by cell division and expansion. The substomatal cavity connecting aerenchyma to stomata formed via programmed cell death (PCD) and was closely associated with guard cell development. Additionally, transcriptome analysis and pharmacological studies revealed that the organization of aerenchyma in greater duckweed is determined by the interplay between PCD and proliferation. This balance is governed by spatiotemporal regulation of phytohormone signaling involving ethylene, abscisic acid, and salicylic acid. Overall, our study reveals the structural dynamics and phytohormonal regulation underlying aerenchyma development in duckweed, improving our understanding of how plants establish distinct architectural arrangements. These insights hold the potential for wide-ranging application, not only in comprehending aerenchyma formation across various plant species but also in understanding how airspaces are formed within the leaves of terrestrial plants.
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Affiliation(s)
- Min Kim
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Do Young Hyeon
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Kyungyoon Kim
- Research Institute of Basic Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Daehee Hwang
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
- Bioinformatics Institute, Bio-MAX, Seoul National University, Seoul 08826, Republic of Korea
| | - Yuree Lee
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
- Plant Genomics and Breeding Institute, Seoul National University, Seoul 08826, Republic of Korea
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2
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Wild AJ, Steiner FA, Kiene M, Tyborski N, Tung SY, Koehler T, Carminati A, Eder B, Groth J, Vahl WK, Wolfrum S, Lueders T, Laforsch C, Mueller CW, Vidal A, Pausch J. Unraveling root and rhizosphere traits in temperate maize landraces and modern cultivars: Implications for soil resource acquisition and drought adaptation. PLANT, CELL & ENVIRONMENT 2024; 47:2526-2541. [PMID: 38515431 DOI: 10.1111/pce.14898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 03/07/2024] [Accepted: 03/11/2024] [Indexed: 03/23/2024]
Abstract
A holistic understanding of plant strategies to acquire soil resources is pivotal in achieving sustainable food security. However, we lack knowledge about variety-specific root and rhizosphere traits for resource acquisition, their plasticity and adaptation to drought. We conducted a greenhouse experiment to phenotype root and rhizosphere traits (mean root diameter [Root D], specific root length [SRL], root tissue density, root nitrogen content, specific rhizosheath mass [SRM], arbuscular mycorrhizal fungi [AMF] colonization) of 16 landraces and 22 modern cultivars of temperate maize (Zea mays L.). Our results demonstrate that landraces and modern cultivars diverge in their root and rhizosphere traits. Although landraces follow a 'do-it-yourself' strategy with high SRLs, modern cultivars exhibit an 'outsourcing' strategy with increased mean Root Ds and a tendency towards increased root colonization by AMF. We further identified that SRM indicates an 'outsourcing' strategy. Additionally, landraces were more drought-responsive compared to modern cultivars based on multitrait response indices. We suggest that breeding leads to distinct resource acquisition strategies between temperate maize varieties. Future breeding efforts should increasingly target root and rhizosphere economics, with SRM serving as a valuable proxy for identifying varieties employing an outsourcing resource acquisition strategy.
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Affiliation(s)
- Andreas J Wild
- Agroecology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
| | - Franziska A Steiner
- Soil Science, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Marvin Kiene
- Animal Ecology I, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
| | - Nicolas Tyborski
- Ecological Microbiology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
| | - Shu-Yin Tung
- Institute for Agroecology and Organic Farming, Bavarian State Research Center for Agriculture, Freising, Germany
- School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Tina Koehler
- Soil Physics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
- Physics of Soils and Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
| | - Andrea Carminati
- Physics of Soils and Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
| | - Barbara Eder
- Institute for Crop Science and Plant Breeding, Bavarian State Research Center for Agriculture (LfL), Freising, Germany
| | - Jennifer Groth
- Institute for Crop Science and Plant Breeding, Bavarian State Research Center for Agriculture (LfL), Freising, Germany
| | - Wouter K Vahl
- Institute for Crop Science and Plant Breeding, Bavarian State Research Center for Agriculture (LfL), Freising, Germany
| | - Sebastian Wolfrum
- Institute for Agroecology and Organic Farming, Bavarian State Research Center for Agriculture, Freising, Germany
| | - Tillmann Lueders
- Ecological Microbiology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
| | - Christian Laforsch
- Animal Ecology I, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
| | - Carsten W Mueller
- Chair of Soil Science, Institute of Ecology, Technische Universitaet Berlin, Berlin, Germany
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark
| | - Alix Vidal
- Soil Biology Group, Wageningen University, Wageningen, The Netherlands
| | - Johanna Pausch
- Agroecology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
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3
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Gholizadeh S, Nemati I, Vestergård M, Barnes CJ, Kudjordjie EN, Nicolaisen M. Harnessing root-soil-microbiota interactions for drought-resilient cereals. Microbiol Res 2024; 283:127698. [PMID: 38537330 DOI: 10.1016/j.micres.2024.127698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 03/14/2024] [Accepted: 03/17/2024] [Indexed: 04/17/2024]
Abstract
Cereal plants form complex networks with their associated microbiome in the soil environment. A complex system including variations of numerous parameters of soil properties and host traits shapes the dynamics of cereal microbiota under drought. These multifaceted interactions can greatly affect carbon and nutrient cycling in soil and offer the potential to increase plant growth and fitness under drought conditions. Despite growing recognition of the importance of plant microbiota to agroecosystem functioning, harnessing the cereal root microbiota remains a significant challenge due to interacting and synergistic effects between root traits, soil properties, agricultural practices, and drought-related features. A better mechanistic understanding of root-soil-microbiota associations could lead to the development of novel strategies to improve cereal production under drought. In this review, we discuss the root-soil-microbiota interactions for improving the soil environment and host fitness under drought and suggest a roadmap for harnessing the benefits of these interactions for drought-resilient cereals. These methods include conservative trait-based approaches for the selection and breeding of plant genetic resources and manipulation of the soil environments.
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Affiliation(s)
- Somayeh Gholizadeh
- Faculty of Technical Sciences, Department of Agroecology, Aarhus University, Forsøgsvej 1, Slagelse 4200, Denmark
| | - Iman Nemati
- Department of Plant Production and Genetics Engineering, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
| | - Mette Vestergård
- Faculty of Technical Sciences, Department of Agroecology, Aarhus University, Forsøgsvej 1, Slagelse 4200, Denmark
| | - Christopher James Barnes
- Faculty of Technical Sciences, Department of Agroecology, Aarhus University, Forsøgsvej 1, Slagelse 4200, Denmark
| | - Enoch Narh Kudjordjie
- Faculty of Technical Sciences, Department of Agroecology, Aarhus University, Forsøgsvej 1, Slagelse 4200, Denmark
| | - Mogens Nicolaisen
- Faculty of Technical Sciences, Department of Agroecology, Aarhus University, Forsøgsvej 1, Slagelse 4200, Denmark.
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4
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Galindo-Castañeda T, Hartmann M, Lynch JP. Location: root architecture structures rhizosphere microbial associations. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:594-604. [PMID: 37882632 PMCID: PMC10773995 DOI: 10.1093/jxb/erad421] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 10/25/2023] [Indexed: 10/27/2023]
Abstract
Root architectural phenotypes are promising targets for crop breeding, but root architectural effects on microbial associations in agricultural fields are not well understood. Architecture determines the location of microbial associations within root systems, which, when integrated with soil vertical gradients, determines the functions and the metabolic capability of rhizosphere microbial communities. We argue that variation in root architecture in crops has important implications for root exudation, microbial recruitment and function, and the decomposition and fate of root tissues and exudates. Recent research has shown that the root microbiome changes along root axes and among root classes, that root tips have a unique microbiome, and that root exudates change within the root system depending on soil physicochemical conditions. Although fresh exudates are produced in larger amounts in root tips, the rhizosphere of mature root segments also plays a role in influencing soil vertical gradients. We argue that more research is needed to understand specific root phenotypes that structure microbial associations and discuss candidate root phenotypes that may determine the location of microbial hotspots within root systems with relevance to agricultural systems.
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Affiliation(s)
| | - Martin Hartmann
- Department of Environmental Systems Service, ETH Zürich, 8092 Zurich, Switzerland
| | - Jonathan P Lynch
- Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA
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5
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Lopez-Valdivia I, Yang X, Lynch JP. Large root cortical cells and reduced cortical cell files improve growth under suboptimal nitrogen in silico. PLANT PHYSIOLOGY 2023:kiad214. [PMID: 37040571 DOI: 10.1093/plphys/kiad214] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/13/2023] [Accepted: 03/13/2023] [Indexed: 06/19/2023]
Abstract
Suboptimal nitrogen availability is a primary constraint to plant growth. We used OpenSimRoot, a functional-structural plant/soil model, to test the hypothesis that larger root cortical cell size (CCS), reduced cortical cell file number (CCFN), and their interactions with root cortical aerenchyma (RCA) and lateral root branching density (LRBD) are useful adaptations to suboptimal soil nitrogen availability in maize (Zea mays). Reduced CCFN increased shoot dry weight over 80%. Reduced respiration, reduced nitrogen content, and reduced root diameter accounted for 23%, 20%, and 33% of increased shoot biomass, respectively. Large CCS increased shoot biomass by 24% compared with small CCS. When simulated independently, reduced respiration and reduced nutrient content increased the shoot biomass by 14% and 3%, respectively. However, increased root diameter resulting from large CCS decreased shoot biomass by 4% due to an increase in root metabolic cost. Under moderate N stress, integrated phenotypes with reduced CCFN, large CCS, and high RCA improved shoot biomass in silt loam and loamy sand soils. In contrast, integrated phenotypes composed of reduced CCFN, large CCS and reduced lateral root branching density had the greatest growth in silt loam, while phenotypes with reduced CCFN, large CCS and high LRBD were the best performers in loamy sands. Our results support the hypothesis that larger CCS, reduced CCFN, and their interactions with RCA and LRBD could increase nitrogen acquisition by reducing root respiration and root nutrient demand. Phene synergisms may exist between CCS, CCFN, and LRBD. CCS and CCFN merit consideration for breeding cereal crops with improved nitrogen acquisition, which is critical for global food security.
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Affiliation(s)
- Ivan Lopez-Valdivia
- Department of Plant Science, The Pennsylvania State University, University Park, PA, U.S.A., 16802
| | - Xiyu Yang
- Department of Plant Science, The Pennsylvania State University, University Park, PA, U.S.A., 16802
| | - Jonathan P Lynch
- Department of Plant Science, The Pennsylvania State University, University Park, PA, U.S.A., 16802
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6
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Kawa D, Brady SM. Root cell types as an interface for biotic interactions. TRENDS IN PLANT SCIENCE 2022; 27:1173-1186. [PMID: 35792025 DOI: 10.1016/j.tplants.2022.06.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 06/04/2022] [Accepted: 06/09/2022] [Indexed: 05/27/2023]
Abstract
Root responses to environmental stresses show a high level of cell type and developmental stage specificity. Interactions with beneficial and pathogenic organisms - including microbes and parasites - elicit a set of transcriptional responses unique to each root cell type, often dependent on their differentiation state. Localized changes to the cell wall and to the integrity of root cell types can serve as a physical barrier for a range of pests. Conversely, certain microorganisms weaken existing barriers within root cell types. Interactions with microorganisms vary between roots of different developmental origins and cellular architectures. Here we provide an overview of the molecular, architectural, and structural properties of root cell types crucial to both maintaining beneficial interactions and protecting from pathogens.
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Affiliation(s)
- Dorota Kawa
- Department of Plant Biology and Genome Center, University of California, Davis, CA 95616, USA.
| | - Siobhan M Brady
- Department of Plant Biology and Genome Center, University of California, Davis, CA 95616, USA.
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7
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Birt HWG, Tharp CL, Custer GF, Dini-Andreote F. Root phenotypes as modulators of microbial microhabitats. FRONTIERS IN PLANT SCIENCE 2022; 13:1003868. [PMID: 36212354 PMCID: PMC9539067 DOI: 10.3389/fpls.2022.1003868] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 09/08/2022] [Indexed: 06/09/2023]
Abstract
Plant roots are colonized by a multitude of microbial taxa that dynamically influence plant health. Plant-microbe interactions at the root-soil interface occur at the micro-scale and are affected by variation in root phenotypes. Different root phenotypes can have distinct impacts on physical and chemical gradients at the root-soil interface, leading to heterogeneous microhabitats for microbial colonization. Microbes that influence plant physiology will establish across these heterogeneous microhabitats, and, therefore, exploiting variation in root phenotypes can allow for targeted manipulation of plant-associated microbes. In this mini-review, we discuss how changes in root anatomy and architecture can influence resource availability and the spatial configuration of microbial microhabitats. We then propose research priorities that integrate root phenotypes and microbial microhabitats for advancing the manipulation of root-associated microbiomes. We foresee the yet-unexplored potential to harness diverse root phenotypes as a new level of precision in microbiome management in plant-root systems.
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8
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Shoaib M, Banerjee BP, Hayden M, Kant S. Roots' Drought Adaptive Traits in Crop Improvement. PLANTS (BASEL, SWITZERLAND) 2022; 11:2256. [PMID: 36079644 PMCID: PMC9460784 DOI: 10.3390/plants11172256] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 08/26/2022] [Accepted: 08/26/2022] [Indexed: 11/16/2022]
Abstract
Drought is one of the biggest concerns in agriculture due to the projected reduction of global freshwater supply with a concurrent increase in global food demand. Roots can significantly contribute to improving drought adaptation and productivity. Plants increase water uptake by adjusting root architecture and cooperating with symbiotic soil microbes. Thus, emphasis has been given to root architectural responses and root-microbe relationships in drought-resilient crop development. However, root responses to drought adaptation are continuous and complex processes and involve additional root traits and interactions among themselves. This review comprehensively compiles and discusses several of these root traits such as structural, physiological, molecular, hydraulic, anatomical, and plasticity, which are important to consider together, with architectural changes, when developing drought resilient crop varieties. In addition, it describes the significance of root contribution in improving soil structure and water holding capacity and its implication on long-term resilience to drought. In addition, various drought adaptive root ideotypes of monocot and dicot crops are compared and proposed for given agroclimatic conditions. Overall, this review provides a broader perspective of understanding root structural, physiological, and molecular regulators, and describes the considerations for simultaneously integrating multiple traits for drought tolerance and crop improvement, under specific growing environments.
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Affiliation(s)
- Mirza Shoaib
- Agriculture Victoria, Grains Innovation Park, 110 Natimuk Road, Horsham, VIC 3400, Australia
- School of Applied Systems Biology, La Trobe University, Bundoora, Melbourne, VIC 3083, Australia
| | - Bikram P. Banerjee
- Agriculture Victoria, Grains Innovation Park, 110 Natimuk Road, Horsham, VIC 3400, Australia
| | - Matthew Hayden
- School of Applied Systems Biology, La Trobe University, Bundoora, Melbourne, VIC 3083, Australia
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 5 Ring Road, Bundoora, Melbourne, VIC 3083, Australia
| | - Surya Kant
- Agriculture Victoria, Grains Innovation Park, 110 Natimuk Road, Horsham, VIC 3400, Australia
- School of Applied Systems Biology, La Trobe University, Bundoora, Melbourne, VIC 3083, Australia
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 5 Ring Road, Bundoora, Melbourne, VIC 3083, Australia
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9
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Galindo-Castañeda T, Lynch JP, Six J, Hartmann M. Improving Soil Resource Uptake by Plants Through Capitalizing on Synergies Between Root Architecture and Anatomy and Root-Associated Microorganisms. FRONTIERS IN PLANT SCIENCE 2022; 13:827369. [PMID: 35356114 PMCID: PMC8959776 DOI: 10.3389/fpls.2022.827369] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/15/2022] [Indexed: 05/14/2023]
Abstract
Root architectural and anatomical phenotypes are highly diverse. Specific root phenotypes can be associated with better plant growth under low nutrient and water availability. Therefore, root ideotypes have been proposed as breeding targets for more stress-resilient and resource-efficient crops. For example, root phenotypes that correspond to the Topsoil Foraging ideotype are associated with better plant growth under suboptimal phosphorus availability, and root phenotypes that correspond to the Steep, Cheap and Deep ideotype are linked to better performance under suboptimal availability of nitrogen and water. We propose that natural variation in root phenotypes translates into a diversity of different niches for microbial associations in the rhizosphere, rhizoplane and root cortex, and that microbial traits could have synergistic effects with the beneficial effect of specific root phenotypes. Oxygen and water content, carbon rhizodeposition, nutrient availability, and root surface area are all factors that are modified by root anatomy and architecture and determine the structure and function of the associated microbial communities. Recent research results indicate that root characteristics that may modify microbial communities associated with maize include aerenchyma, rooting angle, root hairs, and lateral root branching density. Therefore, the selection of root phenotypes linked to better plant growth under specific edaphic conditions should be accompanied by investigating and selecting microbial partners better adapted to each set of conditions created by the corresponding root phenotype. Microbial traits such as nitrogen transformation, phosphorus solubilization, and water retention could have synergistic effects when correctly matched with promising plant root ideotypes for improved nutrient and water capture. We propose that elucidation of the interactive effects of root phenotypes and microbial functions on plant nutrient and water uptake offers new opportunities to increase crop yields and agroecosystem sustainability.
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Affiliation(s)
- Tania Galindo-Castañeda
- Sustainable Agroecosystems, Institute of Agricultural Sciences, Department of Environmental System Science, ETH Zürich, Zurich, Switzerland
| | - Jonathan P. Lynch
- Department of Plant Science, The Pennsylvania State University, University Park, PA, United States
| | - Johan Six
- Sustainable Agroecosystems, Institute of Agricultural Sciences, Department of Environmental System Science, ETH Zürich, Zurich, Switzerland
| | - Martin Hartmann
- Sustainable Agroecosystems, Institute of Agricultural Sciences, Department of Environmental System Science, ETH Zürich, Zurich, Switzerland
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10
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Colombi T, Chakrawal A, Herrmann AM. Carbon supply-consumption balance in plant roots: effects of carbon use efficiency and root anatomical plasticity. THE NEW PHYTOLOGIST 2022; 233:1542-1547. [PMID: 34227122 DOI: 10.1111/nph.17598] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Tino Colombi
- Department of Soil & Environment, Swedish University of Agricultural Sciences, PO Box 7014, Uppsala, 75007, Sweden
| | - Arjun Chakrawal
- Department of Physical Geography, Stockholm University, Svante Arrhenius Väg 8C, Frescati, Stockholm, 10691, Sweden
- Bolin Centre for Climate Research, Stockholm University, Stockholm, 10691, Sweden
| | - Anke Marianne Herrmann
- Department of Soil & Environment, Swedish University of Agricultural Sciences, PO Box 7014, Uppsala, 75007, Sweden
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11
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Variations in Arbuscular Mycorrhizal Colonization Associated with Root Diameter and Hypodermis Passages Cells across Temperate and Tropical Woody Species. FORESTS 2022. [DOI: 10.3390/f13020140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Root hypodermis passage cells (PCs) lack suberin and lignin deposition, responsible for nutrient absorption and arbuscular mycorrhizal colonization, which are crucial for root resource acquisition. Nevertheless, their quantitative variability across diverse woody species and their relationships with root morphology and anatomy, as well as arbuscular mycorrhizal colonization, are still not well understood. Herein, the number and proportion of PCs in the root cross-section, root morphology, anatomy, and arbuscular mycorrhizal colonization rate were quantified across 10 temperate and 12 tropical woody species. The objectives of this study were to determine how PCs vary across contrasting environmental conditions and to explore their relationships with arbuscular mycorrhizal colonization rate and other root functional traits. The results showed that tropical species possessed 56% more PCs than temperate species; by contrast, they had similar proportions of PCs. In both biomes, the number of PCs had a tightly positive correlation with arbuscular mycorrhizal colonization rate (R2 = 0.35–0.87), root diameter (R2 = 0.84–0.93), and cortex thickness (R2 = 0.87–0.89), but the proportion of PCs was mostly independent of root morphological and anatomical traits. Our results suggest that variation in passage cells could well explain the tight linkage between arbuscular mycorrhizal colonization and root diameter across species and biomes, which provides insight into the collaboration gradient between plant roots and mycorrhizal fungi that dominates the root economics space.
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12
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Strock CF, Lynch JP. Root secondary growth: an unexplored component of soil resource acquisition. ANNALS OF BOTANY 2020; 126:205-218. [PMID: 32588876 PMCID: PMC7523590 DOI: 10.1093/aob/mcaa068] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Indexed: 05/06/2023]
Abstract
BACKGROUND AND AIMS Despite recent progress in elucidating the molecular basis of secondary growth (cambial growth), the functional implications of this developmental process remain poorly understood. Targeted studies exploring how abiotic and biotic factors affect this process, as well as the relevance of secondary growth to fitness of annual dicotyledonous crop species under stress, are almost entirely absent from the literature. Specifically, the physiological role of secondary growth in roots has been completely neglected yet entails a unique array of implications for plant performance that are distinct from secondary growth in shoot tissue. SCOPE Since roots are directly responsible for soil resource capture, understanding of the fitness landscape of root phenotypes is important in both basic and applied plant biology. Interactions between root secondary growth, edaphic conditions and soil resource acquisition may have significant effects on plant fitness. Our intention here is not to provide a comprehensive review of a sparse and disparate literature, but rather to highlight knowledge gaps, propose hypotheses and identify opportunities for novel and agriculturally relevant research pertaining to secondary growth of roots. This viewpoint: (1) summarizes evidence from our own studies and other published work; (2) proposes hypotheses regarding the fitness landscape of secondary growth of roots in annual dicotyledonous species for abiotic and biotic stress; and (3) highlights the importance of directing research efforts to this topic within an agricultural context. CONCLUSIONS Secondary growth of the roots of annual dicots has functional significance with regards to soil resource acquisition and transport, interactions with soil organisms and carbon sequestration. Research on these topics would contribute significantly toward understanding the agronomic value of secondary growth of roots for crop improvement.
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Affiliation(s)
- Christopher F Strock
- Department of Plant Science, The Pennsylvania State University, University Park, PA, USA
| | - Jonathan P Lynch
- Department of Plant Science, The Pennsylvania State University, University Park, PA, USA
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