Phosphorous Uptake

1
Phosphorous Uptake

• P is found in organic inorganic forms
• Up to 80 of P is unavailable
• Largely immobile (d.r. 1 attometer per s)
• Soil available P usually less 10 mM
• Organic P slowly mineralized
• Can be accessed by phosphatases

2
pH and P availability
3
Roots Mycorrhizae

• Plants maximize absorption area
• Root hair and root caps secrete mucilage
• Creates hydration sheath contains
  polysaccharides
• Fungus food

4
Mycorrhizae

• Myco fungi rhizae root
• Mutualistic symbiotic relationship between fungus
  and plant
• Ancient association
• In nature 90 of plants infected with MR
• 83 DICOTS
• 79 MONOCOTS
• 100 GYMNOSPERMS

5
Mycorrhizae

• Only a few plant families (3) do not form
  associations with MR
• Some plants have an absolute reproductive
  requirement for MR association
• MR are classified as ectoMR or endoMR or
  intermediate MR 3 others

6
Mycorrhizae

• Increase water uptake in plant
• Increase mineral uptake especially P, Cu Zn
• How?
• Improve soil texture

7
Mycorrhizae

• Nutrient exchange occurs in the intercellular
  spaces or cells
• Up to 20 of plant carbon is allocated to
  mycorrhizae
• Mycorrhizae extend root area
• Mycorrhizae can penetrate smaller crevices than
  root hairs

8
Mycorrhizae

• Fungal mycelium metabolically less expense to
  maintain for the plant than extended root system
• Mycelium can sequester heavy metals (Os, Pb)
• Mycelium limits uptake of Al, As, Ti. Ba Cd)

9
Mycorrhizae

• Offers additional biochemical pathways to plant
• MR are reported to improve abiotic and abiotic
  stress tolerance
• antibiotic production
• MR may form plant to plant network
• Allows for nurturing of seedlings in understories
  where light is limiting

10
Ectomycorrhizae

• EctoMR are members of the basidomycetes or the
  ascomycetes
• Infect Pinaceae, Fabaceae, and temperature
  forests
• Form a sheath around the root
• The mass of the hyphae mass of roots

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Ectomycorrhizae

• Hyphae grow between the spaces in the cortical
  root cell
• Forms a network called Hartig net
• No cellular penetration by the hyphae
• Reproductive spores are formed in the soil only

12
Endomycorrhizae

• Belong mainly to Glomalae family
• Were called VAM (vesicular arbuscular
  mycorrhizae)
• Infect grasses, most herbaceous dicots, many
  perennial shrubs and 6 genera of gymnosperms

13
Endomycorrhizae

• Dont form a Hartig net
• Hyphae grow into intercellular spaces of cortical
  cells, but penetrate cell walls
• Direct cell to cell exchange of nutrients
• Hyphae form arbuscles (Bulb structure) where they
  penetrate plant cell
• Spores can form inside or outside of plant cell

14
Other Mycorrhizae

• Ectendomycorrhizae (Ericaceous MR)
• Intermediate in habit
• Hyphae penetrate cortical cells, but no arbuscle
  formed
• Infect Ericaceous plants - largely woody shrubs
  (i.e. bearberry, rhododendron, labrador tea
  plant)

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Other Mycorrhizae

• Orchidae Mycorrhizae
• Only infect orchids
• Orchids cannot grow without infection
• Endomycorrhizae but no arbuscles
• Many achlorophyllous orchids parasitize their MR

16
Mycorrhizae and Agriculture

• Many agricultural practices are detrimental to MR
  development
• Tillage destroys network
• Summerfallow and/or chemfallow destroys MR hosts
• Canola in field decreases MR populations

17
Mycorrhizae and Agriculture

• MR show some host specificity, therefore crop
  rotations impact on MR populations
• Excess P availability results in plants not
  allowing the association - decreases MR
  population
• Therefore certain fertilizer regimes can be
  counter productive

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Mycorrhizae and Agriculture

• Many inoculants available
• Forestry and citrus orchards
• Problems
• mycelium better inoculant in many cases
• difficult to grow in culture
• species specificity reduces effective range

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Other Microbial Agents

• Pseudomonas sp Bacillus megaterium
• PGPBs Or PSBs
• Work through 1 of 2 mechanisms
• Phytohormones secretion improve root growth
• Secretion of acid compound which solubilize
  phosphate
• Aspergillis sp.

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JUMPSTART or PROVIDE

• Penicillium bilaii
• Solubilizing fungi?
• Registered as an inoculum for many crops
  including canola
• PHILOM BIOS LTD
• Also Aspergillis sp.