Lecture 8: Acquiring phosphorus Flashcards
Proteoid roots known as
Cluster roots
Proteoid roots also known as
cluster roots
is phosphate renewable?
NO.
its essential but a non-renewable resource
Is phosphorous inorganic or organic?
-Phosphorus is an essential inorganic nutrient
what % of P applied as fertiliser is bound to
80-90%
to soil particles and is highly immobile. Mass flow typically delivers as little as 1–5 % of plant P demand.
what % of P applied as fertilisers to soil is bound and highly immobile
80-90% Mass flow typically delivers as little as 1-5% of plant P demand
How can P supply be improved?
Root interception of Pi can be increased by root proliferation (cluster or proteoid roots) (the exceptions)
and mycorrhizal symbioses (the rule)
species with proteiod roots can grow in
solid with poorly available nutrients; most do not form mycorrhizal symbioses
cluster roots has a increased/decreased root surface area
massive increase in root surface area (up to 25-fold)
Cluster (proteoid) roots exude compounds facilitating the:
mobilisation of nutrients from soil. Organic anions, especially citrate, mobilise P by chelating soil minerals such as Fe, Al, Ca which bind P. Acid phosphotases hydrolyse organic forms of P
exudative burst refers to
the rootlets exude little or no material until fully grown, but then, over a few days, exude large amounts of citrate and malate. Then exudation drops back to almost zero. May prevent soil bacteria from depleting the exudates.
exudation of cluster roots requires how much input of carbon from the shoot
MASSIVE
50-100% when active, 10-30% over a season
is phosphate renewable resource?
No. is essential but will run out eventually
phosphorous is an essential organic/inorganic nutrient?
inorganic
after N whats the most important inorganic nutrient for plants
P
nucleic acids, metabolites, phospholipids etc
what % of P applied as fertiliser is bound to
80-90%
to soil particles and is highly immobile. Mass flow typically delivers as little as 1–5 % of plant P demand.
How can P supply be improved?
Root interception of Pi can be increased by root proliferation (cluster or proteoid roots) (the exceptions)
and mycorrhizal symbioses (the rule)
species with proteiod roots can grow in
soils with poorly available nutrients; most do not form mycorrhizal symbioses
Cluster (proteoid) rots provide affect on root surface area
MASSIVE INCREASE
up too 25-fold
cluster roots exude compounds facilitating the
mobilisation of nutrients from the soil
In cluster roots what are the organic anions role
Organic anions, especially citrate, mobilize P by chelating soil minerals such as Fe, Al, and Ca, which bind P. Acid phosphatases hydrolyze organic forms of P
in proteoid roots whats the ‘exudative burst’
the rootlets exude little or no material until fully grown, but then, over a few days, exude large amounts of citrate and malate. Then exudation drops back to almost zero. May prevent soil bacteria from depleting the exudates.
Proteoid roots: exudation requires
massive input of carbon from the shoot (50-100% when active, 10-30% over a season)
Hakea victoria & Banksia speciosa (western australia)
Proteaceae in south‐western Australia occur on severely P‐impoverished soils. They have very low leaf P concentrations, but relatively fast rates of photosynthesis, suggesting they do not compromise their metabolic machinery in order to save P.
