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Natural ecosystems and agricultural production have been threatened by multifaceted global environmental changes. Soil degradation, extreme drought and flooding events, shifting climatic patterns and other challenges have prompted many disciplines within plant science to pivot to find solutions. Accordingly, root research has expanded from fundamental studies on roots, as providers of physical support, water and essential nutrients uptake, towards identification of beneficial traits for stress adaptation and control of key biological soil processes. Advances in trait identification, data acquisition, management and modelling are enabling root researchers to develop predictive models to support ecosystems in these changing environments. Through technical presentations, posters, industry exhibits and a root phenotyping workshop, the international, jointly presented, completely virtual International Society of Root Research (ISRR) 11/Rooting2021 meeting provided a unique platform for researchers across disciplines to share recent advances in root biology, from molecular to ecosystem-level scales, in agricultural and natural ecosystems, addressing critical questions in response to climate change and its impact on crop productivity and ecosystem services. In this report, the 2021 ISRRAmbassador cohort provides an overview of the current root research landscape and reflection on the importance of frontier research for a more sustainable future.
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Meetings
Root biology never sleeps
11
th
Symposium of the International Society of Root
Research (ISRR11) and the 9
th
International
Symposium on Root Development (Rooting2021),
2428 May 2021
Emerging frontiers: root and rhizosphere research in
the context of global environmental change
Natural ecosystems and agricultural production have been threat-
ened by multifaceted global environmental changes. Soil degrada-
tion, extreme drought and flooding events, shifting climatic
patterns and other challenges have prompted many disciplines
within plant science to pivot to find solutions. Accordingly, root
research has expanded from fundamental studies on roots, as
providers of physical support, water and essential nutrients uptake,
towards identification of beneficial traits for stress adaptation and
control of key biological soil processes. Advances in trait identi-
fication, data acquisition, management and modelling are enabling
root researchers to develop predictive models to support ecosystems
in these changing environments.
Through technical presentations, posters, industry exhibits and a
root phenotyping workshop, the international, jointly presented,
completely virtual International Society of Root Research (ISRR)
11/Rooting2021 meeting provided a unique platform for
researchers across disciplines to share recent advances in root
biology, from molecular to ecosystem-level scales, in agricultural
and natural ecosystems, addressing critical questions in response to
climate change and its impact on crop productivity and ecosystem
services. In this report, the 2021 ISRR Ambassador cohort provides
an overview of the current root research landscape and reflection on
the importance of frontier research for a more sustainable future.
ISRR11 and Rooting2021: A joint, virtual meeting
In response to global travel restrictions imposed by the COVID-19
pandemic, the 11
th
Symposium of the International Society of
Root Research (ISRR11, https://www.rootresearch.org/) and the
9
th
International Symposium on Root Development (Root-
ing2021) merged into a single online event co-organised by the
Interdisciplinary Plant Group at the University of Missouri
(Columbia, MO, USA) and the University of Nottingham (UK).
Over 700 participants representing academia, government and
industry from more than 53 countries (Supporting Information
Fig. S1) joined the virtual event held 2428 May 2021. The
schedule ran almost uninterrupted across international time zones,
featuring 74 talks (10 plenaries, 16 keynotes, and 48 invited) and c.
300 posters, spanning a broad range of disciplines. In addition, the
2021 ISRR Lifetime Achievement Award was presented to Wendy
Silk, Emeritus Professor at the University of California-Davis
(USA).
The Ambassador Program
ISRR11/Rooting2021 hosted the 3
rd
ISRR Ambassador Program,
a unique platform for early-career root researchers. The virtual
ISRR11/Rooting2021 Ambassador Program provided networking
activities, experience with conference organisation, interaction
with professionals in diverse career areas, and opportunities to
discuss advances in the field with a broadly multidisciplinary
cohort (Notes S1). Ambassador tasks at the ISRR11/Rooting 2021
meeting included session note-taking, the production of this
Meeting report, and a set of recommendations for diversity and
inclusion in future scientific events (Notes S2).
Root phenotyping workshop
The ISRR11/Rooting2021 meeting concluded with a root
phenotyping workshop with virtual tours of major root pheno-
typing facilities and demonstrations of methods. Organised by
Larry York (Oak Ridge National Laboratory, TN, USA) and
Darren Wells (University of Nottingham, UK), in collaboration
with other experts and the ISRR Ambassadors, the workshop with a
Q&A format was used to discuss the latest advances in root
phenotyping techniques. The potential complementarity of image
analysis software tools emerged as a key topic as depicted in Fig. S2.
The availability of standardised protocols for root collection and
trait measurement was also highlighted by the participants of
the online survey, organised by the Ambassadors in addition to
the Symposium (Delory et al., 2022) and the workshop as an
important issue for future research. The Root Ecology Handbook
recently published in New Phytologist provides a comprehensive
guide on root sampling, processing and measuring for a wide
variety of traits in a standardised manner (Freschet et al., 2021).
Stress-resilient crops as a root phenotyping target
Root phenotyping for traits related to crop performance or
ecosystem services has been a main focus in the field of root biology
since the 1970s (Hurd, 1974). However, quantitative analysis of
plant phenotypes and their linkages to plant functions remains a
major bottleneck. ISRR11/Rooting2021 highlighted the current
emphasis on phenotyping root traits that will provide resilience to
changing environmental conditions (Fig. 1), including traits
related to rootmicrobial interactions (Kawasaki et al., 2021).
Rhizosphere processes related to root stress responses are key for
sustainable food production systems, as they impact soil function-
ing and resource use efficiency.
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The impact of drought and limited nutrient supply on plants
under global climate change, and the mechanisms of root response
from molecular to field scales, have prompted focussed advances on
well established areas in the field of root research. Therefore, the
role of auxin and cytokinin in molecular crosstalk has prompted the
rise of the ‘hormonics’ to explore their functions in root
development under drought stress (Rodriguez-Alonso et al., 2018),
and to identify signalling pathways that link nutrient availability to
root developmental parameters (Shahzad & Amtmann, 2017).
Hormonal signalling also underlies ‘nutritropism’, an extension of
‘chemotropism’ (Newcombe & Rhodes, 1904), which can now
be explored with advanced imaging and microscopy technology
(T. Fujiwara, University of Tokyo, Japan). Root-related strategies
to mitigate drought stress related to root hydraulic architecture and
water transport were also discussed (Maurel & Nacry, 2020). Root-
system-level traits linked with water and nutrient use efficiency such
as wheat root axial conductance (Hendel et al., 2021), architectural
traits in rice (Ruangsiri et al., 2021) and maize (Kistler et al., 2018)
have been identified with a combination of shovelomics, pheno-
typing, functional genomics and modelling.
The long-standing challenges of grafting for the introduction of
root traits related to stress tolerance have been partially overcome by
recent progress on our understanding of graft compatibility and
cell-to-cell adhesion (Notaguchi et al., 2020). Advancing our
understanding of grafting mechanisms will certainly provide new
avenues to understand the effects of specific root genotypes and/or
traits on other parts of the plant body (J. Cantillo, Donald
Danforth Plant Science Center, MO, USA).
Current trends in root research seek to integrate stress responses
inside the root system with a better understanding of these root
soilmicrobe interactions. ISRR11/Rooting2021 highlighted the
role of the rhizosphere microbiome in nutrient homeostasis, for
example, in root diffusion (Salas-Gonzalez et al., 2021), or during
nitrogen acquisition (Arsova et al., 2012). Root exudates were
introduced as potential targets for rhizosphere engineering to
promote beneficial microbiome functionalities (Kawasaki et al.,
2021) or to control harmful species. Novel studies looking into
rootmicrobiome interactions have become possible due to
precision genome editing, production of knocked-down lines
and reconstruction of biosynthetic metabolic pathways (Huang
et al., 2019), and advanced imaging techniques such as positron
emission tomography (Schmidt et al., 2020).
Roadmap to high-throughput root phenotyping
Recent advances in imaging techniques and image analysis (Fig. 1)
can support high-throughput root phenotyping of relevant struc-
tural features within the root architecture (Fig. 2). Detailed image-
based root phenotyping techniques such as X-ray computed
tomography (CT) scanning can improve our interpretation of in-
field studies (C. Topp, Donald Danforth Plant Science Center,
MO, USA). Current advances allow high-resolution and/or high-
throughput phenotyping studies, even in mature crops and under
field conditions (Gore et al., 2020; Rich et al., 2020), although
methodological challenges remain (Delory et al., 2022). For
example, root phenotyping of rooting depth and its significance
for deep water or nitrate uptake is being addressed with large-scale
field experiments using minirhizotrons or soil coring on maize
(A. Leakey, University of Illinois, USA), wheat (J. Christopher,
University of Queensland, Australia) and potatoes (O. Popovic,
Copenhagen University, Denmark). Automated, high-resolution
minirhizotrons are also used for visualising the dynamics of roots
and fungi interaction in experimentally warmed peatlands (C.
Iversen, Oak Ridge National Laboratory, TN, USA; Defrenne
et al., 2020). These imaging advances are complemented by the
development of free, open source and high-performance image
analysis software (Fig. S2).
Pairing 3D imaging techniques (e.g. X-ray CT) with mathemat-
ical modelling is a powerful way to study plantsoil interactions on
different scales, from soil pores to growing root systems (Roose
et al., 2016). This hybrid approach has resulted in key milestones by
Fig. 1 Schematic overview of root phenotyping targets and methodological
approaches discussed at the ISRR11/Rooting2021. The scheme highlights
root system traits of interest for plant adaptation to stress, agricultural
production and ecosystem services. Relevant methodological approaches to
identify root traits are highlighted, including imaging techniques, rhizobiome
analysis and rhizosphere metabolomics. Comprehensive collections of root
image analysis and modelling tools are currently available (Lobet, 2017).
Further phenotyping approaches such as the measurement of ion uptake
rates and mechanical measurements were also discussed throughout the
meeting. A detailed list can be found in the results of the phenotyping survey
(Delory et al., 2022).
New Phytologist (2022) 235: 2149–2154
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Ó2022 The Authors
New Phytologist Ó2022 New Phytologist Foundation.
Meetings
Forum
New
Phytologist
2150
allowing the elucidation of how root architecture and exudation
jointly affect P mobilisation and uptake (McKay Fletcher et al.,
2020), and to quantify the extent to which the dissolution of N
fertiliser granules affects soil microbial activity (Ruiz et al., 2020).
Imaging techniques can also be used for traits related to root
microbe interactions (Fig. 1), complementing other multidisci-
plinary approaches that seek to better understand the complex
dialogue between roots, the associated microbiome and soil
processes.
Unleashing the power of mathematical modelling
Mathematical modelling complements phenotyping advances by
overcoming the challenges of experimental approaches and benefits
from the emerging field of functional phenomics (York, 2019).
Highlights from the diversity of modelling approaches presented at
ISRR/Rooting2021, in both spatial and temporal scales, include: a
micro-hydrological model that describes a new symplastic water
pumping mechanism (Couvreur et al., 2021); the dynamics and
regulation of a fast brassinosteroid response pathway in Ara bidopsis
root tips (Großeholz et al., 2021); functionalstructural plant
(FSP) models to identify optimal root phenotypes for nutrient
capture in contrasting environments (Rangarajan, 2021); and field-
scale simulations of plant populations and communities (Postma
et al., 2017; Schnepf et al., 2018; Faverjon et al., 2019). Future
mathematical models will draw on larger, more complex, datasets
incorporating novel imaging technology, high-throughput pheno-
typing and availability of relevant environmental data. The positive
feedback cycles between these models and continued advances in
phenotyping are what will surely advance the field of root science.
Concluding remarks and perspectives
To meet the challenges imposed by the global COVID-19
pandemic, online communication has provided new opportunities
for international multidisciplinary cooperation. The ISRR11/
Rooting2021 online event brought the root research community
together to share knowledge on the latest developments in root and
rhizosphere research, present new technological advances and
identify pressing research questions that still require answers. The
adoption of a holistic approach to root research, that is, one that
takes into account all categories of root traits, from anatomy to root
(a) (b)
(c)
Fig. 2 Nondestructive, high-resolution and
3D imaging techniques offer new insights into
the hidden half of plants. (a) Image of a
soybean root system with N
2
-fixing nodules
obtained using X-ray computed tomography.
(b) Combining positron emission tomography
and X-ray computed tomography allows the
visualisation of carbon allocation to the N
2
-
fixing nodules of a soybean root system.
(c) Visualising the architecture and internal
anatomy of a maize root system using X-ray
computed tomography and X-ray microscope
images. Photography credits: Christopher
Topp (Donald Danforth Plant Science Center,
MO, USA).
Ó2022 The Authors
New Phytologist Ó2022 New Phytologist Foundation.
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New
Phytologist Meetings Forum 2151
morphology, physiology and architecture, as well as interactions
with the rhizosphere microbiota, was emphasised as a crucial step in
facing the challenges posed by global change. We encourage root
researchers to actively take advantage of the plethora of online
resources currently available for plant phenotyping (https://
quantitative-plant.org/), and to join the ISRR (https://www.
rootresearch.org/). Collaborations to share knowledge, along with
new technological advances, will help us further understand roots
and rhizosphere processes.
Acknowledgements
The authors thank the New Phytologist Foundation for supporting
the Ambassador Program, and John Kirkegaard and Hallie
Thompson for initiating the ISRR Ambassador Program in 2015.
LAG acknowledges support from the Plant Genome Research
Program, National Science Foundation (IOS-1444448). We thank
Michelle Watt, Bob Sharp, Malcolm Bennett and the organisers of
the ISRR11/Rooting2021 Symposium from the Interdisciplinary
Plant Group at the University of Missouri (Columbia, USA) and
the University of Nottingham (UK). In particular, the authors
would like to thank Victoria Bryan as well as Jennifer Hartwick and
her team for their exceptional support. We thank Larry York and
Darren Wells for organising an excellent virtual root phenotyping
workshop during the ISRR11/Rooting2021 conference with
generous financial support from the International Plant Pheno-
typing Network. The ISRR Ambassadors are also very grateful to
Charlie Messina, Michelle Watt, Genevieve Croft and Ronald
Vargas for sharing their professional experience and for taking the
time to discuss career opportunities for root scientists. The authors
thank Christopher Topp, Larry York and Abraham Smith for their
contributions to the preparation of the figures. Finally, thanks to all
ISRR11/Rooting2021 participants for making this conference a
success!See you at the next ISRR (organised in 2024 in Leipzig,
Germany) and/or Rooting (organised in 2023 in Ghent, Belgium)
conference.
Competing interests
None declared.
Author contributions
AJM, CNT, LAG and AT coordinated the ‘ISRR11 Ambassador
Program’ and provided valuable feedback on the manuscript. The
ISRR11 Ambassadors group (CNC, GC, KKD, BMD, AD, YD,
APG, QH, P-WH, MCH-S, ML, JLPN, LM, JM-M, AER, JS,
TSW, PW, XW, LX, CZ) compiled and collated minutes of the
sessions throughout the meeting and wrote the initial draft and the
revised versions. Ambassador JS prepared Notes S2 addressing
diversity and inclusion at ISRR11/Rooting2021.
ORCID
Clayton N. Carley https://orcid.org/0000-0003-2067-1891
Guanying Chen https://orcid.org/0000-0003-3308-2252
Krishna K. Das https://orcid.org/0000-0002-9521-978X
Benjamin M. Delory https://orcid.org/0000-0002-1190-8060
Anastazija Dimitrova https://orcid.org/0000-0003-2581-5487
Yiyang Ding https://orcid.org/0000-0001-6031-1263
Abin P. George https://orcid.org/0000-0001-7392-9353
Laura A. Greeley https://orcid.org/0000-0002-6200-3798
Qingqing Han https://orcid.org/0000-0002-6298-2826
Pieter-Willem Hendriks https://orcid.org/0000-0002-2419-
9646
Maria C. Hernandez-Soriano https://orcid.org/0000-0002-
8006-9192
Meng Li https://orcid.org/0000-0002-6411-3085
Lisa Mau https://orcid.org/0000-0003-1737-8547
Jennifer Mesa-Marın https://orcid.org/0000-0001-8450-7906
Allison J. Miller https://orcid.org/0000-0002-2722-9361
Jason Liang Pin Ng https://orcid.org/0000-0002-8714-8870
Angus E. Rae https://orcid.org/0000-0001-8235-3907
Jennifer Schmidt https://orcid.org/0000-0001-7403-5829
August Thies https://orcid.org/0000-0002-2537-4354
Christopher N. Topp https://orcid.org/0000-0001-9228-6752
Tomke S. Wacker https://orcid.org/0000-0002-1493-2699
Pinhui Wang https://orcid.org/0000-0003-0718-065X
Xinyu Wang https://orcid.org/0000-0002-8982-9733
Limeng Xie https://orcid.org/0000-0002-6642-504X
Congcong Zheng https://orcid.org/0000-0001-8989-8221
Data availability
Data sharing is not applicable to this article as no datasets were
generated or analysed during the current study.
Clayton N. Carley
1
, Guanying Chen
2
,
Krishna K. Das
3
, Benjamin M. Delory
4
*,
Anastazija Dimitrova
5
, Yiyang Ding
6
,
Abin P. George
3
, Laura A. Greeley
7
, Qingqing Han
8
,
Pieter-Willem Hendriks
9,10,11
,
Maria C. Hernandez-Soriano
12
*, Meng Li
13
,
Jason Liang Pin Ng
14
, Lisa Mau
15,16,17
,
Jennifer Mesa-Marın
18
, Allison J. Miller
19,20
,
Angus E. Rae
14
, Jennifer Schmidt
21
,
August Thies
20,22
, Christopher N. Topp
20
,
Tomke S. Wacker
2
, Pinhui Wang
14
, Xinyu Wang
23
,
Limeng Xie
24
and Congcong Zheng
15,16
*
1
Department of Agronomy, Iowa State University,
Ames, IA 50011, USA;
2
Department of Plant and Environmental Sciences, University of
Copenhagen, Frederiksberg C, 1871, Denmark;
3
Division of Biology, Indian Institute of Science Education and
Research Tirupati, Tirupati 517507, India;
4
Institute of Ecology, Leuphana University of
Luneburg, Luneburg 21335, Germany;
5
Department of Biosciences and Territory, University of Molise,
Pesche 86090, Italy;
6
Department of Forest Sciences, University of Helsinki,
Helsinki, FI-00014, Finland;
New Phytologist (2022) 235: 2149–2154
www.newphytologist.com
Ó2022 The Authors
New Phytologist Ó2022 New Phytologist Foundation.
Meetings
Forum
New
Phytologist
2152
7
Department of Biochemistry & Interdisciplinary Plant Group,
University of Missouri-Columbia, Columbia, MO 65201, USA;
8
State Key Laboratory of Grassland Agro-ecosystems, College of
Pastoral Agriculture Science and Technology, Lanzhou University,
Lanzhou 730020, China;
9
CSIRO, Agriculture and Food, PO Box 1700,
Canberra, 2601 ACT, Australia;
10
School of Agriculture and Wine Sciences, Charles Sturt
University, Boorooma Street, 14 Wagga Wagga,
NSW 2650, Australia;
11
Graham Centre for Agricultural Innovation, Locked bag 588,
Wagga Wagga, NSW 2678, Australia;
12
Department of Biochemistry and Metabolism, John Innes
Centre, Norwich, NR4 7UH, UK;
13
Department of Plant Science, The Pennsylvania State University,
State College, PA 16801, USA;
14
Research School of Biology, Australian National University,
Canberra, 2601 ACT, Australia;
15
Institute of Bio- and Geosciences Plant Sciences (IBG-2),
Forschungszentrum Julich GmbH, Julich 52425, Germany;
16
Faculty of Agriculture, University of Bonn,
Bonn 53115, Germany;
17
School of BioSciences, The University of Melbourne,
Melbourne, 3010 VIC, Australia;
18
Department of Plant Biology and Ecology, Universidad de
Sevilla, Seville 41012, Spain;
19
Department of Biology, Saint Louis University, St Louis,
MO 63103, USA;
20
Donald Danforth Plant Science Center, St Louis,
MO 63132, USA;
21
Cocoa Plant Sciences, Mars Wrigley Davis, CA 95616, USA;
22
Division of Plant Sciences, University of Missouri-Columbia,
Columbia, MO 65201, USA;
23
Institute of Grassland Science, Northeast Normal University,
Key Laboratory of Vegetation Ecology, Ministry of Education, Jilin
Songnen Grassland Ecosystem National Observation and Research
Station, Changchun 130024, China;
24
Department of Plant Biology, University of Georgia, Athens,
GA 30605, USA
(*Authors for correspondence: email: maria.hernandez-sori-
ano@jic.ac.uk, mceclipse.soriano@gmail.com (MCH-S);
benjamin.delory@leuphana.de, delory.benjamin@gmail.com
(BMD); co.zheng@fz-juelich.de, zhengcc342@gmail.com (CZ))
References
Arsova B, Kierszniowska S, Schulze WX. 2012. The use of heavy nitrogen in
quantitative proteomicsexperiments in plants. Trends in Plant Science 17:102112.
Couvreur V, Heymans A, Lobet G, Draye X. 2021. Evidence for a multicellular
symplasmic water pumping mechanism across vascular plant roots. bioRxiv:
2021.04.19.439789.
Defrenne CE, Childs J, Fernandez CW, Taggart M, Nettles WR, Allen MF,
Hanson PJ, Iversen CM. 2020. High-resolution minirhizotrons advance our
understanding of rootfungal dynamics in an experimentally warmed peatland.
Plants People Planet 3:113.
Delory BM, Hernandez-Soriano MC, Wacker TS, Dimitrova A, Ding Y, Greeley
LA, Ng JLP, Mesa-Marın J, Xie L, Zheng C et al. 2022. A snapshot of the root
phenotyping landscape in 2021. bioRxiv: 2022.01.28.478001.
Faverjon L, Escobar-Gutierrez A, Litrico I, Julier B, Louarn G. 2019. A generic
individual-based model can predict yield, nitrogen content, and species
abundance in experimental grassland communities. Journal of Experimental
Botany 70: 24912504.
Freschet GT, Pages L, Iversen CM, Comas LH, Rewald B,Roumet C, KlimesovaJ,
Zadworny M, Poorter H, Postma JA et al. 2021. A starting guide to root ecology:
strengthening ecological concepts and standardising root classification, sampling,
processing and trait measurements. New Phytologist 232: 9731122.
Gore MA, Brown P, Spalding EP, Leakey A. 2020. Machine learning enabled
phenotyping for GWAS and TWAS of WUE traits in 869 field-grown sorghum
accessions. bioRxiv: 2020.11.02.365213.
Großeholz R, Wanke F, Glockner N, Rausch L, Rohr L, Scholl S, Scacchi E,
Spazierer A-J, Shabala L, Shabala S et al. 2021. Computational modeling and
quantitative cell physiology reveal central parameters for the brassinosteroid-
regulated cell growth of the Arabidopsis root. bioRxiv: 2021.04.13.439595.
Hendel E, Bacher H, Oksenberg A, Walia H, Schwartz N, Peleg Z. 2021.
Deciphering the genetic basis of wheat seminal root anatomy uncovers ancestral
axial conductance alleles. Plant, Cell & Environment 44: 19211934.
Huang AC, Jiang T, Liu Y-X, Bai Y-C, Reed J, Qu B, Goossens A, Nutzmann H-
W, Bai Y, Osbourn A. 2019. A specialized metabolic network selectively
modulates Arabidopsis root microbiota. Science 364: eaau6389.
Hurd EA. 1974. Phenotype and drought tolerance in wheat. Agricultural
Meteorology 14:3955.
Kawasaki A, Dennis PG, Forstner C, Raghavendra AKH, Richardson AE, Watt M,
Mathesius U, Gilliham M, Ryan PR. 2021. The microbiomes on the roots of
wheat (Triticum aestivum L.) and rice (Oryza sativa L.) exhibit significant
differences in structure between root types and along root axes. Functional Plant
Biology 48: 871888.
Kistler L, Yoshi Maezumi S, de Souza JG, Przelomska NAS, Costa FM, Smith O,
Loiselle H, Ramos-Madrigal J, Wales N, Ribeiro ER et al. 2018. Multiproxy
evidence highlights a complex evolutionary legacy of maize in South America.
Science 362: 13091313.
Lobet G. 2017. Image analysis in plant sciences: publish then perish. Trends in Plant
Science 22: 559566.
Maurel C, Nacry P. 2020. Root architecture and hydraulics converge for
acclimation to changing water availability. Nature Plants 6: 744749.
McKay Fletcher DM, Ruiz S, Dias T, Petroselli C, Roose T. 2020. Linking root
structure to functionality: the impact of root system architecture on citrate-
enhanced phosphate uptake. New Phytologist 227: 376391.
Newcombe FC, Rhodes AL. 1904. Chemotropism of roots. Botanical Gazette 37:
2234.
Notaguchi M, Kurotani K-I, Sato Y, Tabata R, Kawakatsu Y, Okayasu K, Sawai Y,
Okada R, Asahina M, Ichihashi Y. 2020. Cell-cell adhesion in plant grafting is
facilitated by b-1,4-glucanases. Science 369: 698702.
Postma JA, Kuppe C, Owen MR, Mellor N, Griffiths M, Bennett MJ, Lynch JP,
Watt M. 2017. OpenSimRoot: widening the scope and application of root
architectural models. New Phytologist 215: 12741286.
Rangarajan H. 2021. Exploring the root phenome: simulation modeling with a
functional structural plant model. PhD thesis, The Pennsylvania State University,
State College, PA, USA.
Rich SM, Christopher J, Richards R, Watt M. 2020. Root phenotypes of
young wheat plants grown in controlled environments show inconsistent
correlation with mature root traits in the field. Journal of Experimental Botany
71: 47514762.
Rodriguez-Alonso G, Matvienko M, Lopez-Valle ML, L
azaro-Mixteco PE,
Napsucialy-Mendivil S, Dubrovsky JG, Shishkova S. 2018. Transcriptomics
insights into the genetic regulation of root apical meristem exhaustion and
determinate primary root growth in Pachycereus pringlei (Cactaceae). Scientific
Reports 8:111.
Roose T, Keyes SD, Daly KR, Carminati A, Otten W, Vetterlein D, Peth S. 2016.
Challenges in imaging and predictive modeling of rhizosphere processes. Plant
and Soil 407:938.
Ruangsiri M, Vejchasarn P, Saengwilai P, Lynch J, Bennett MJ, Brown KM,
Chutteang C, Boonruangrod R, Shearman J, Toojinda T et al. 2021. Genetic
control of root architectural traits in KDML105 chromosome segment
substitution lines under well-watered and drought stress conditions. Plant
Production Science 24:118.
Ó2022 The Authors
New Phytologist Ó2022 New Phytologist Foundation.
New Phytologist (2022) 235: 2149–2154
www.newphytologist.com
New
Phytologist Meetings Forum 2153
Ruiz SA, McKay Fletcher DM, Boghi A, Williams KA, Duncan SJ, Scotson CP,
Petroselli C, Dias TGS, Chadwick DR, Jones DL et al. 2020. Image-based
quantification of soil microbial dead zones induced by nitrogen fertilization.
Science of the Total Environment 727: 138197.
Salas-Gonzalez I, Reyt G, Flis P, Custodio V, Gopaulchan D, Bakhoum N,
Dew TP, Suresh K, Franke RB, Dangl JL. 2021. Coordination between
microbiota and root endodermis supports plant mineral nutrient homeostasis.
Science 371: eabd0695.
Schmidt MP, Mamet SD, Ferrieri RA, Peak D, Siciliano SD. 2020. From the
outside in: an overview of positron imaging of plant and soil processes. Molecular
Imaging 19: 1536012120966405.
Schnepf A, Leitner D, Landl M, Lobet G, Mai TH, Morandage S, Sheng C,
Zoerner M, Vanderborght J, Vereecken H. 2018. CRootBox: a structural
functional modelling framework for root systems. Annals of Botany 121: 1033
1053.
Shahzad Z, Amtmann A. 2017. Food for thought: how nutrients regulate root
system architecture. Current Opinion in Plant Biology 39:8087.
York LM. 2019. Functional phenomics: an emerging field integrating high-
throughput phenotyping, physiology, and bioinformatics. Journal of Experimental
Botany 70: 379386.
Supporting Information
Additional Supporting Information may be found online in the
Supporting Information section at the end of the article.
Fig. S1 Map depicting the distribution and number of attendees to
the joined Symposium ISRR11-Rooting2021.
Fig. S2 Example of root image analysis pairing RootPainter and
RhizoVision explorer.
Notes S1 The ISRR11 3
rd
Graduate Student and Postdoc
Ambassador Program.
Notes S2 Diversity and inclusion at ISRR11/Rooting2021.
Please note: Wiley Blackwell are not responsible for the content or
functionality of any Supporting Information supplied by the
authors. Any queries (other than missing material) should be
directed to the New Phytologist Central Office.
Key words: Ambassador Program, ISRR11, rhizosphere, root phenotyping, root
traits, Rooting2021, roots.
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New Phytologist Ó2022 New Phytologist Foundation.
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