Microbial association with vascular plants Plants—the major source of organic matter on which most soil microorganisms are dependent. Different Microorganisms are associated with the leaves, stems, flowers, seeds, and roots. The microbial community influences plants in direct and indirect ways.

2. • Plants—the major source of organic matter on which
most soil microorganisms are dependent.
• Different Microorganisms are associated with the leaves,
stems, flowers, seeds, and roots.
• The microbial community influences plants in direct and
indirect ways.

3. Commensalism
• One partner is
benefited other
neither hurt nor
helped
Mutualism
• Both the partners
are benefited
Pathogenic
• Damage the host

4. Epiphytes Endophytes
Microbes
that live
on the
surface
of the
plants
Microbes
that
colonize
internal
plant
tissues
Those
microbes that
live above –
ground level /
aerial
Those that
inhabit
below-ground
level

5. • Phyllosphere – the environment of the aerial portion of the plant
(leaves, stem, flowers, friuts & seeds) inhabited by microorganisms.
• Phylloplane – the leaf surface.
• Ruinen coined the term ‘’Phyllosphere’’
• Once assumed that aerial portion does not support stable microbial
community becoz of
• Rapid changes in humidity
• UV exposure
• Temperature
• Now known that phyllosphere is home for diverse assortment of
Results in the
fluctuations in the
leaching of organic
material like simple
sugars.
1. Phyllosphere

6. Spermosphere
The phyllosphere can be
further subdivided into
 Caulosphere (stems)
 Phylloplane (leaves)
 Anthosphere (flowers)
 Carposphere (fruits)
 Spermosphere (seeds)

7. • Supports bacteria, filamentous fungi, yeast &
photosynthetic & heterotropic protists.
• Important spp are – γ Proteobacteria, Pseudomonas
syringae, Erwinia, Pantoea spp., Pseudobacterium,
Phytomonas, Sarcina.
• Abundant bacterial genus – Sphingomonas (survive
under high level of UV irradiation)– produces a pigment
that function like a sun screen.
• This bacterium, also common in soils and waters, can
occur at 108 cells per gram of plant tissue.

8. Nitrogen fixing bacteria Beijerinckia & Azotobacter
Cyanobacteria Anabaena, Nostoc, Calothrix, Scytonema,
Tolypothrix
Fungi Cladosporium, Alternaria, Cercospora, Rodotorula,
Torulopsis, Oidium, Puccinia, Melanospora,
Saccharomyces, Candida, Penicillium,
Cephalosporium, Fusarium, Colletotrichum.
Actinomyces &
Streptomyces

9. • Microbes controls the spread of air borne pathogens.
• Spores of pathogen attaches to the surface of
leaves/plant pathogen attacks the leaf.
• Microorganisms gets activated
• Produce ‘’elicitor’’
• This activates the plant to produce ‘’Phytoalexins’’
• Attacks the pathogen

10. Elicitor
Biotic
Polysaccharides
(fungi), lipids,
microbial
enzymes &
polypeptides.
Abiotic
Heavy metal
salts, autoclaved
ribonuclease,
cold & UV light
Plants Phytoalexins
Potato Chlorogenic acid (CA), catteic
acid
Pea Pisatin
Green
bean
Phaseolin
Soybean Hydroxyphaseolin
Carrot CA & 6-methoxymellein (MM)
Apple Phloridzin & Phloretin
Tobacco Scopoletin, Scopolin, Benzoic
acid

11. • Term Rhizosphere was coined by Hiltner.
• Rhizosphere - Root exudates create a unique
environment for soil microorganisms.
• Rhizoplane – plant root surface
• Rhizosphere effect (RE) – the overall influence of plant
root on soil microorganisms.

12. Soil type
Moisture
pH
Temperatur
e
Age of the
plant
Condition
of the plant

13. • Catalyses the breakdown of organic material
• Eg: oxidoreductase
• Hydrolases
• Lyases
• Transferases
• Cellulase
• Urease
• Dehydrogenase

14. • R:S ratio = No. of microorganisms in rhizosphere soil
No. of microorganisms in root free soil

15. • Gram negative, non sporulating, rod shape bacteria
• Pseudomonas, Arthrobacter, Agrobacterium,
Azotobacter, Mycobacterium, Flavobacter,
Cellulomonas, Micrococcus.
• Nitrogen fixing bacteria – Azotobacter, Acetobacter,
Azospirillum

16. Plant
(root exudates)
Rhizosphere microbes
Enhance
growth
Protects
microbes
 Protect from plant pathogens
 Improves the nutrient availability
 Enhance plant growth by
producing growth promoting
substances
 Root hair development
 Mucilage secretion
 Lateral root development
Root exudates
 Aminoacids
 Sugars
 Organic acids
 Vitamins
 Nucleotides
Growth promoting
substances
 Auxins
 Gibberelins
 Cytokinins
 Glycolipids

17. • Mycorrhizae are fungus-root associations, first
discovered by Albert Bernhard Frank in 1885.
• Mycorrhizae – fungus root (greek)
• It’s a mutualistic relationship b/w most plants & limited
number of fungal species.
• Both partners depends on the activities of the other and
have coevolved.
• Fungi colonize about 80% of all higher plants, ferns &
mosses.

18. They do not obtain
organic carbon from
the degradation of
organic material
They use photo
synthetically derived
carbohydrate
provided by their
host

19. Enhance the nutrient uptake
Increases the plant biomass
Increases the photosynthetic rate of the plant

21. Mycorrhiza
e
Ectomycorrhiz
ae or sheathed
mycorrhizae
Remain extracellularly
& forms sheath of
interconnecting hyphae
around the roots
Endomycorrhiz
ae or
Arbuscular
mycorrhizae
Fungi that enters the
root cells

22. • Formed by ascomycete & basidiomycete fungi.
Plant colonization:
• ECM colonize almost all trees & woody plants in cooler
climates.
• Fungal/plant colonization is species specific.
Function:
• Transfer nutrients – nitrogen, phosphorous to the root.

23. ECM fungal mycelium grow around the root
Mycelium thickens & forms sheath or mantle (entire root is covered by the fungal mycelium).
ECM produce signalling molecules that limits the growth of root hairs (fungi itself function like
root hairs).
From the root surface, fungal hyphae extends into the soil.
These hyphal filaments aggregates to form Rhizomorphs (visible to the naked eye).
Hyphae on the inner side of the sheath penetrate b/w the cortical cells (but not within) & form a
mesh like hyphae called Hartig net.

24. Plant
Ectomycorrhizae
Provide carbohydrate – mannitol,
Trehelose (cannot used by the
plants)
Uptake nutrients – N,
P
Soil nutrients
Rhizomorphs
Hyphal sheath
Hartig net filaments
Root cells

25. • “Mycorrhization helper bacteria” (MHB) – helps in the
development of the mycorrhizal relationships with the
ectomycorrhizal fungus.
• Bacterial symbionts also are found in the cytoplasm of AM
fungi.
• Bacterialike organisms (BLOs) - related to Burkholderia
cepacia. These “trapped” bacteria contribute to the nitrogen
metabolism of the plant-fungal complex by assisting with the
synthesis of essential amino acids.
• More than 5,000 species of fungi, predominantly
Carbon flow
Plant
Mycorrhizal
hyphal network
Surrounding soil.
Helps in the
formation of
‘Mycorrhizospher
e’

26. • Also called as arbuscular mycorrhizae or AM fungi due its
characteristic intracellular structure called the arbuscule.
• It is the most common type of mycorrhizae.
• Associated with many tropical plants esp. crop plants - wheat,
corn, beans, tomatoes, apples, oranges, and many other
commercial crops, as well as grasses.
• AM fungi belongs to Glomeromycota division.

27. DEVELOPMENTAL PROCESS
The fungal hyphae enter into the root cells b/w the plant cell wall
& invaginates the plasma membrane
They do not breach the root cell membrane.
Within the folds of the plasma membrane it forms a treelike
hyphal networks called arbuscules.
Life span of invidual arbuscules – 2 weeks
AM is a vigourous colonizers

28. Nutrient uptake & transfer – N, P
Protects the plant host from disease
Increase drought resistance
Reduce pest & nematode infection
Facilitate soil aggregation
Promote seed production

29. • This mycorrhizal fungi are saprophytic.
• Orchids are –
unusual plants, function like parasite.
Never produce chlorophyll (nonphotosynthetic), other produce
after maturation.
Cannot produce photosynthetically derived carbon.
Orchid seeds do not germinate with out the help of Orchid
mycorrhizal fungi (Basidiomycete)
Organic
matter
Carbon
Orchid mycorrhizal fungi
Decomposition
Utilized by
Orchid plant
Orchid mycorrhizal fungi

30. Wet environments
• Increase the
availability of
nutrients
Arid environments
• Aid in water
uptake
• Allow increased
transpiration
rates

31. Mycorrhizae
Fungi
involved
Plants colonized
Fungal structural
features
Fungal funtions
Ectomycorrhizae Basidiomycetes
Ascomycetes
90% of trees in temperate
region (species specific)
Rhizomorphs
Sheath/ mantle
Hartig net
Nutrient uptake (N&P) &
transfer
Ectendomycorrhiz
ae
Ascomycetes Conifers Hartig net with some
intracellular hyphae
Nutrient uptake
Mineralization of organic
matter
Monotropoid
mycorrhizae
Basidiomycetes
Ascomycetes
Flowering plants that lack
chlorophyll (eg: indian
pipe)
Hartig net with one cell
deep in the root cortex
Nutrient uptake
Arbuscular
mycorrhizae
Glomeromycete
s
Crop plants & tropical
trees (not species
specific)
Arbuscules Nutrient uptake (N&P) &
transfer
Promote seed production
Orchidaceous
mycorrhizae
(Saprophytic)
Basidiomycetes orchids Hyphal coils called
pelotons within host
tissue
Provide organic carbon &
nutrients
Ericaceous
mycorrhizae
Basidiomycetes
Ascomycetes
low evergreen shrubs &
heathers
Some intracellular &
some extracellular
Mineralization of organic
matter
Ectomycorrhizae
Endomycorrhizae