Root exudates play an important role in plant nutrition by interacting with soil microbes and influencing the rhizosphere. Root exudates include primary metabolites like amino acids, carbohydrates, organic acids, and secondary metabolites like flavonoids, lignins, coumarins, and fatty acids. These exudates are released from the root tip through passive diffusion and active transport processes. They function to attract beneficial microbes, chelate nutrients, and defend against pathogens in the rhizosphere. The composition and concentration of root exudates varies depending on plant species and environmental conditions like nutrient availability.
intro-classification-salt accumulation in soil imapairs plant function and soil structure-physiological effects on crop growth and development-osmotic effect and specific ion effects-plant use different strategies to avoid salt injury
Plant microbe interaction by dr. ashwin chekeAshwin Cheke
PLANT MICROBE – INTERACTIONS AND THEIR MUTUAL BENEFITS IN ENHANCING SOIL HEALTH AND AGRICULTURAL PRODUCTION ,
IT ALSO INCREASE CROP PRODUCTIVITY AND IMPROVE SOIL HEALTH
intro-classification-salt accumulation in soil imapairs plant function and soil structure-physiological effects on crop growth and development-osmotic effect and specific ion effects-plant use different strategies to avoid salt injury
Plant microbe interaction by dr. ashwin chekeAshwin Cheke
PLANT MICROBE – INTERACTIONS AND THEIR MUTUAL BENEFITS IN ENHANCING SOIL HEALTH AND AGRICULTURAL PRODUCTION ,
IT ALSO INCREASE CROP PRODUCTIVITY AND IMPROVE SOIL HEALTH
Substances containing carbon are organic matter.
Soil organic matter consists of decomposing plant and animal residues.
It also includes substances of organic origin either leaving or dead.
Substances containing carbon are organic matter.
Soil organic matter consists of decomposing plant and animal residues.
It also includes substances of organic origin either leaving or dead.
EXPLORING PHOSPHATE-SOLUBILIZING ASPERGILLUS SP: ISOLATION AND OPTIMIZATION O...indexPub
Background: The global phosphorus crisis is an evolving concern as the world's phosphorus sources are running out and demand for agricultural production is rising. Phosphorus shortages undermine food security and demand long-term management practices to assure phosphorus availability. Methods: Aspergillus strains were first screened on PVK media to get phosphorus solubilizing species and then the best strain was used to produce acid phosphatases. Finally, the effect of various assay conditions was analyzed to characterize extracellular acid phosphatases. Results: Out of four isolated strains, only A. niger, A. oryzae, and A. flavus were able to solubilize phosphate on PVK, of which A. niger stood out with a maximum solubility index of 2.38. The optimal pH and temperature for enzyme activity were recorded as 4.5 and 30°C. Furthermore, the substrate concentration of 100 mM with a 40-minute incubation period was found as a standard condition to achieve maximum specific activity i.e. 12 U/mg and a 17% higher free phosphorus level. After optimization, a 43.8% increment in the activity of extracellular acid phosphatases was observed. Conclusion: The study concludes that A. niger was the prominent performer, with improved phosphate solubilization and enzyme activity, as well as higher phosphorus release, demonstrating its potential for enhancing phosphorus availability not only in agricultural and environmental fields but in setups with lower phosphate availability too.
Root is the part where plant interact with microbes. Microbes really plays an important role in the overall wellbeing of the crop. Here is some basics regarding root colonization
Can changes in root anatomical traits during stress enhance drought & Salini...kabeya
There are array of ways of studying plant response to drought or any kind of stress, ranging from physiological, morphological, cellular level, biochemical, anatomical or even at molecular level. This presentation deals or shows how plant tissues can respond under stress at anatomical level and hence contribution to tolerance.
Can changes in root anatomical traits during stress enhance drought & Salini...kabeya
There are array of ways of studying plant response to drought or any kind of stress, ranging from physiological, morphological, cellular level, biochemical, anatomical or even at molecular level. This presentation deals or shows how plant tissues can respond under stress at anatomical level and hence contribution to tolerance.
If you want to explore the role of Cyanobacteria in soil fertility in general & Azolla-Anabena association in particular, you can visit this PowerPoint Presentation.
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National Biodiversity protection initiatives and Convention on Biological Di...PABOLU TEJASREE
Biological Diversity Act, 2002
The Biological Diversity Act, 2002 was passed by the parliament of India to protect biodiversity
and facilitate the sustainable management of biological resources with the local communities.
The Act was enacted to meet the requirements stipulated by the United Nations Convention on
Biological Diversity (CBD), to which India is a party.
Agrobacterium and other methods of plant transformation including gene gun, i...PABOLU TEJASREE
The process of transfer, integration and expression of transgene in the host cells is known as genetic transformation. A foreign gene (transgene) encoding the trait must be incorporated into plant cells, along with a "cassette" of extra genetic material to add a desirable trait to a crop. The cassette includes a sequence of DNA called a "promoter", which determines where and when the foreign gene is expressed in the host, and a "marker gene" which allows breeders to determine by screening or selection which plants contain the inserted gene. For example, marker genes may make plants resistant to antibiotics not used routinely (e.g., agrimycin, kanamycin) or tolerant of some herbicides.
Agrobacterium and other methods of plant transformation including gene gun, i...PABOLU TEJASREE
Genetic transformation is a powerful tool and a significant strategy for studying plant functional genomics, i.e. gene exploration, new insights into gene regulation, and the analysis of genetically regulated characteristics. Furthermore, the work of isolated genes utilizing map-based cloning of mutant alleles has been verified through functional complementation via genetic transformation. In addition, genetic engineering allows the insertion of alien genes into crop plants and the accelerated creation of new genetically modified organisms.
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Conclusion: Integrating diverse transgenes and gene editing with omics approaches enhances stress tolerance and nutritional content in biofortified crops. This holistic strategy enables precise modifications to crop genomes and comprehensive insights into stress responses and nutrient metabolism, ensuring sustainable food production and nutrition security.
QTL MAPPING AND APPROACHES IN BIPARENTAL MAPPING POPULATIONS.pptxPABOLU TEJASREE
• The loci controlling quantitative traits are called quantitative trait loci or QTL.
• Term first coined by Gelderman in 1975.
Principles of QTL mapping
• Genes and markers segregate via chromosome recombination during meiosis, thus allowing their analysis in the progeny.
• The detection of association between phenotype and genotype of markers.
• QTL analysis depends on the linkage disequilibrium.
• QTL analysis is usually undertaken in segregating mapping populations.
Key steps for the QTL mapping
• Collection of parental strains that differ for traits of interest
• Selection of molecular markers such as RFLP, SSR and SNP that distinguish between the two parents
• Development of a mapping population
• Genotyping and phenotyping of the mapping population
• Detection of QTL using a suitable statistical method
• For practical purposes, in general recombination events considered to be less than 10 recombinations per 100 meiosis, or a map distance of less than 10 centi Morgans(cM).
Patents
Patent is an exclusive ownership right granted by a country to the owner of an invention for a limited period of time, provided the invention satisfies certain conditions stipulated in the law.
Letters Patent (a kind of certificate) name of an instrument granted by the government to convey a right to the patentee. It is issued to the owner of the invention by the patent office of the country conferring this right.
Exclusivity of right implies that no one else can make, use, manufacture or market the invention without the consent of the patent holder.
A patent in the law is a property right and hence, it can be gifted, inherited, assigned, sold or licensed. The right is conferred by the State and it can be revoked by the state under very special circumstances for the benefit of public even if the patent has been sold or licensed or manufactured or marketed in the mean time. The patent right is territorial in nature i.e., a patent granted in India can only be enforced in India.
Disclosure of an invention is a legal requirement for obtaining a patent. The patentee must disclose the invention in a patent document for people to practice it after the expiry of the term of patent or after the patent has lapsed due to nonpayment of maintenance fee or practice it with the consent of the patent holder during the life of the patent.
Patent system in India
1856: The first legislation in India relating to patents was the Act VI of 1856. The objective of this legislation was to encourage inventions of new and useful manufactures and to induce inventors to disclose secret of their inventions.
1859: Fresh legislation for granting ‘exclusive privileges’ was introduced as Act XV of 1859. This legislation contained certain modifications of the earlier legislation. This Act excluded importers from the definition of inventor.
1872: “The Patents and Designs Protection Act” was enacted.
1883: The protection of invention was created
1888: The Act was consolidated as the Inventions and Design Act
1911: The Indian Patents and Designs Act was created
1972: The Patents Act, 1970 came into force on 20th April, 1972. Later amended in 1999, 2002,
2005, 2006, 2012, 2014 and 2016.
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karyotype: Karyotype is the chromosome complement of an individual defined by the identifying characteristics of number and appearance of chromosomes, relative arm length, banding pattern, centromere position, secondary constriction and presence of satellite in decreasing order
Karyogram : study of a whole set of chromosomes arranged in pairs by size and position of centromere
Types of karyotypes:
Symmetric karyotype is defined as the small difference between the largest and smallest chromosome as well as more number of metacentric chromosomes in a chromosome complement.
Asymmetric karyotype is defined as the huge difference between the largest and smallest chromosome as well as less number of metacentric chromosomes in a chromosome complement
Determination of chromosome shape:
Chromosome shape can also be defined in terms of the centromeric index or the arm ratio.
The centromeric index is the length of the shorter arm divided by the total chromosome length, and thus varies from 0.5 for a truly metacentric chromosome to zero for a telocentric one.
The arm ratio is the length of the long arm divided by the length of the short arm, and thus ranges from unity for a truly metacentric chromosome to infinity for a truly telocentric chromosome.
Quantification of degree of asymmetry:
Four ratios between the sizes of smallest and longest chromosomes (1,2,3,4) and three different proportions of metacentric chromosomes (A,B,C,D) in the karyotype.
So that 12 classes of karyotypes are possible in the increasing order of asymmetry
Increased karyotype asymmetry was associated with specialised zygomorphic flowers
Ideogram: it is a schematic diagrammatic representation of a karyotype that shows all the homologous pairs of chromosomes in the nucleus.
Advantages of karyotyping:
• Reveals the structural features of each chromosome
• Helps in studying chromosome banding pattern
• Helps in identifying chromosomal aberrations
• Detection of prenatal genetic disorders
• Aids in studying evolutionary changes
Chromosome banding
Chromosome banding: When subjected to different treatments before staining, the chromosomes develop different dark and light regions in form of bands – chromosome banding.
• This is a technique for the identification of chromosomes and its structural abnormalities in the chromosome complement.
• Chromosome identification depends on their morphological characteristics such as relative length, arm ratio, presence and absence of secondary constrictions on the chromosome arms.
• It is an additional and useful tool for the identification of individual chromosome within the chromosome complement.
• It could be used for identification of chromosome segments that predominantly consist of either GC or AT rich regions or constitutive heterochromatin.
• On banded chromosome, darkly stained or brightly fluorescent transverse bands (positive bands) alternate with the lightly stained or less fluorescent (negative bands).
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This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
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Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
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This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
3. Rate of exudates increases by the presence of microbes in
the rhizosphere becoz soil microbes release compounds
such as 2,4-diacetylphloroglucinaol & Zearalenone that
stimulate root exudation of primary metabolites ex:-
Amino acids
5. ⃰Coumarins : Umbelliferone
⃰Aurones : Benzyl aurones synapates, sinapoyl choline
⃰Glucosinolates:Cyclobrassinone,desuphoguconapin,desulphoprogoitrin,,desulphoglucoalyssin
⃰Anthocyanins : Cyanidin, delphinidin, pelargonidin
⃰Indole compounds :Indole-3-acetic acid, brassitin, sinalexin, brassilexin, methyl indole
carboxylate, camalexin glucoside
⃰Fatty acids : Linoleic acid, oleic acid, palmitic acid, stearic acid
⃰Sterols : Campestrol, sitosterol, stigmasterol
⃰Allomones: Jugulone, sorgoleone, 5′-dimethoxyflavone, DIMBOA, DIBOA
⃰Proteins and enzymes : PR proteins, lectins, proteases, acid phosphatases, peroxidases,
hydrolases, lipase
List of components presented in this table is reported mainly from the model plant Arabidopsis (see Narasimhan et al. 2003)
6.
7. COMPONENT RHIZOSPHERE FUNCTION
PHENOLICS
Chemoattractant signals to microbes
Nod gene inducers in rhizobia
Detoxifiers of Al
Phytoalexins against soil pathogens
ORGANIC ACIDS
Chemoattractant signals to microbes
Nod gene inducers in rhizobia
Chelators of poorly soluble mineral nutrients
Detoxifiers of Al
AMINOACIDS AND
PHYTOSIDEROPHORES
Chelators of poorly soluble mineral nutrients
Chemoattractant signals to microbes
VITAMINS Promoters of plant and microbial growth
ENZYMES Catalysts for P release from organic molecules
ROOT BORDER CELLS
Stimulate microbial growth
Release chemo attractants
Release mucilage and proteins
PURINES Nutrient source
8. Techniques to study chemistry of Root
Exudates
* Infrared Spectroscopy (IR)
* Solid State Nuclear Magnetic Resonance Spectroscopy
using the Carbon 13 isotope (C-13 SSNMR) and proton
(H-1) NMR
* Gas chromotography with Mass spectroscopy (GS/MS)
* Cine-photomicrography
* Cryo scanning electron and transmission electron
microscopy
* Patch clamp technique
9. Introduction
...
Van Egeraat (1975) demonstrated that the root tips of the primary and lateral roots were sites of exudation by
spraying ninhydrin on the filter paper where the plant roots grew.
Ninhydrin is a chemical compound that interacts specifically with amine groups to produce a purple colour.
Using ninhydrin is still considered an important tool to identify the sites of exudation on roots, but the
limitation of using it is that it is able to detect only amino acids or ninhydrin-positive compounds in the
exudates.
McDougall & Rovira (1970) used 14C-labelled compounds to identify the sites of exudation from wheat
roots, and noticed that diffusible material released from the whole length of roots
Frenzel (1957, 1960) reported that different compounds were released from different parts of root system.
Asparagine and threonine from the meristem and root elongation zone; glutamic acid, valine, leucine and
phenylalanine from root hair zone; and aspartic acid from the whole root.
10. Generally, the apical meristem root tip wends its way through the soil . It has been proposed that these
sloughed-off cap cells play a significant of plant roots is covered by a group of cells arranged in layers called
the root cap, which sloughs off as the role in determining the rhizosphere ecology, and therefore the term
‘border cells’ was proposed (Hawes 1990).
Border cells are involved in several functions: they decrease frictional resistance experienced by root tips ,
they regulate microbial interactions through avoidance of harmful microbes (pathogens) and favouring
associations with beneficial microbes (PGPR) and they protect against heavy metal toxicity such as aluminium
A mucilaginous layer has been observed on the surface of roots, particularly at the root tip, where it can form a
droplet in the presence of water . This secretion may derive from the root cap or from the degradation of
epidermal cell walls
13. TRANSPORT
Root exudation is a complex phenomenon encompassing processes that drive C transport to roots and
exudation from roots to soil. The long distance transport of C produced in source organs takes place in the
phloem, through the widely accepted Munch’s pressure-driven mechanism of phloem flow .
According to this mechanism, phloem metabolites are transported by a difference in turgor between sink
and source organs generated by concentration gradients, which are determined by source-sink
activities .
RELEASE OF PRIMARY METABOLITES AT THE ROOT TIP
14.
15. Release Of Primary Metabolites At The Root Tip…
⃰ Phloem unloading occurs through plasmodesmata (combination of mass flow and diffusion). During
unloading, low-molecular-weight solutes and proteins are diverted into the phloem-pole pericycle, a tissue
connected to the protophloem by a unique class of “funnel plasmodesmata” . While proteins are
released in discrete pulses (referred to as “batch unloading”)
⃰ The discovery made by Ross-Elliott et al. (2017) is very important in connection to root exudation at the
root tip . The principal route for all solutes to be unloaded and that they will move toward the surrounding
cells through diffusion because of the high degree of plasmodesmatal connections in this area
17. Movement Of Primary Metabolites Outside
The Root Tip
⃰ While metabolites can move quite freely through the symplastic pathway, in
order to be excreted to the soil environment, they need to pass through at least one
plasma membrane to reach the apoplast .
⃰ Therefore, these molecules only transit the plasma membranes through specific
transmembrane proteins, which form small pores through the lipid bilayer,
allowing polar or charged molecules to cross the membrane without interacting
with the hydrophobic fatty acid chains of the membrane phospholipids
18. Solutes move through symplast and apoplast , but when
are retaken up casparian strip limit the apoplast pathway.
cortex and epidermis are responsible for apoplast .
Both symplast and apoplast pathways are used
becoz of lack of casparian strip
Differentiated region Undifferentiated region
19. Transport………..
Traditionally, root exudation has been suspected to be a passive process mediated by diffusion, channels,
and vesicle transport.
However, recent studies elucidated a pivotal role of tightly regulated primary and secondary active
transport processes across the root plasma membrane in the export and accumulation of defense
phytochemicals in the rhizosphere.
Two protein families involved in mediating the transport of a wide array of organic substances, namely
multidrug and toxic compound extrusion (MATE) and ATP-binding cassette (ABC) transporters
In the case of MATE transporter proteins, a subclade that can be found in all plants analyzed so far is
implicated in the release of citrate into the rhizosphere to confer aluminum resistance to plants.
Recently, a MATE transporter in the stele of rice roots was found to facilitate efflux of phenolic
compounds into the xylem.
20. ABC transporters are involved in diverse cellular processes, such as the excretion of potential toxic
compounds, lipid translocation, heavy metal tolerance, nutrient transport, salt stress and in disease
resistance
Study reported that the secretion of genistein , a signal flavonoid involved in rhizobium symbiosis secreted
from soy bean roots, was mediated by an ABC transporter by an ATP-dependent manner, which was
demonstrated by using the specific ABC transporter inhibitor sodium orthovanadate
Plant roots secrete citric, oxalic and malic acids to detoxify aluminium in the soils , and the secretions of
these organic acids are highly specific to aluminium stress.
Phosphorus deficiency also results in enhanced root secretion of phenolic compounds in certain tree and
legume species, and the specificity of organic acid secretion in response to P deficiency varies with plant
species
While P deficient in rape typically releases malic acid near its root tips or at sites in contact with insoluble
rock phosphate, P-starved hedge mustard does not secrete organic acids
21. – Catechin , a potential allelotoxin produced by spotted knapweed through increased secretion of oxalic
acid, which protects the roots against damage incurred by reactive oxygen species (ROS) resulting from
interactions with the allelochemical .
– Benzoxazinoids , found in the root exudates of maize attract plant-beneficial microbe interaction .
– Prescence of PGPR B. subtilis invokes abscisic acid and salicylic acid signaling pathways in A.thaliana ,
resulting in the closure of stomata and thus restrict the pathogen entry .
– Flavanoids present in the root exudates of legumes that activate Rhizobium meliloti genes responsible for
the nodulation process .
– High concentrations of Organic acids in root exudates lead to P def and this lowers the pH making Mn , Fe
and Zn to be more available in calcareous soil.
– As micronutrient def occur in high concentration below 5.5 pH can cause some major macronutrients to
become limiting . However , Organic acids are able to solubilize unavailable soil macronutrients – Ca .
22. Mechanisms of root exudation of compounds through the plant cell
membranes
Antimicrobial flavonoids
3-deoxyanthocyanidins
accumulate on sorghum
leaves at sites of fungal
infection
23. Exudation
mechanisms through
the plasma membrane
at the root tip
Top panel – active transport
mechanisms (primary or secondary ).
Against electrochemical gradient .
the bottom panel – passive transport
mechanism ( diffusion ) following
electrochemical gradient
24. Functions –Case studies
– N&P acquisition by root exudates
– Role of root exudates in plant to plant signalling
– The Influence of Root Exudates on Symbiotic Relationships in an
Intercropping System
– Role of root exudates in N cycle - Root Exudates as a Means To
Mitigate Agricultural Nitrogen Losses
25.
26. Roles of root
exudates in plant-
to-plant signalling
Allelopathic plants release allelochemicals to
inhibit the growth of neighbouring roots
(Asaduzzaman et al., 2016; Macías et al.,
2019).
Neighbouring plants must then detect the
presence of allelopathic species and adjust root
placement to avoid these allelochemicals.
If they do not alter root placement, their roots
should be inhibited by allelochemicals,
representing a benefit to the allelopathic plant
and a cost to the target.
Accordingly, root-placement patterns may be
driven by both allelochemicals and signalling
chemicals released from interacting
neighbours' root exudates
27. * Root exudates that specifically inhibit
soil nitrification have been identified in
important crop species, including rice,
wheat, and sorghum, while others have
been shown to stimulate root
nodulation and N2 fixation, even in
neighboring plants.
28. Major N transformations in the soil - that are catalyzed by specific enzymes, including various nitrate
reductases (NAS, NAR, NAP, and EUK-NR), nitrite reductases (NIR, NRF), nitric oxide reductase (NOR), nitrous
oxide reductase (NOS), nitrogenase (NIF), ammonia monooxygenase (AMO), hydroxylamine oxidoreductase (HAO),
nitrite oxidoreductase (NXR), and hydrazine hydrolase (HH)
ROOT EXUDATES
29. Root Exudates as a
Means To Mitigate
Agricultural
Nitrogen Losses
Biological nitrification
inhibitors (BNIs) released
from root exudates
suppress nitrification via
AMO and HAO inhibition
30. Category Compound Source Comments
BNIs from
root exudates
Sorgoleone Sorghum bicolor Blocks AMO and HAO;
allelopathic compound
Sakuranetin Sorghum bicolor Blocks AMO and HAO;
noneffective BNI in soil assay;
phytoalexin
Methyl 3-(4-
hydroxyphenyl) Sorghum bicolor
propionate Blocks AMO; infuences root
system architect
Brachialactone Brachiaria humidicola Blocks AMO and HAO;
Reduces Field-level nitrication and
N2O emission
1,9-Decanediol Oryza sativa Blocks AMO; release correlated to NUE
31. The Influence of Root
Exudates on Symbiotic
Relationships in an
Intercropping System
In a maize–faba bean intercropping
system, root exudates from maize
(e.g., flavonoids such as genistein)
can stimulate rhizobial Nod factors,
as well as nodulation and biological
N2 fixation (BNF) in faba bean roots,
thereby enhancing N nutrition,
biomass, and yield.
In exchange, root exudates
containing fixed N (e.g., NH4 + ,
amino acids, etc.) can be transferred
from faba bean to maize, thus also
benefiting N nutrition, growth, and
yield of maize.
32. References
– Coskun, D., Britto, D.T., Shi, W and Kronzucker, H.J.2017. How plant root exudates
shape the nitrogen cycle. Trends in Plant Science. 22 (8): 661-673.
– Badri, D.V. and Vivanco, J.M., 2009. Regulation and function of root
exudates. Plant, cell & environment, 32(6), pp.666-681.
– Baetz, U. and Martinoia, E., 2014. Root exudates: the hidden part of plant
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– Bais, H.P., Weir, T.L., Perry, L.G., Gilroy, S. and Vivanco, J.M., 2006. The role of
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