The infection process during nodule organogenesis ─ occur simultaneously
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Transcript of The infection process during nodule organogenesis ─ occur simultaneously
The infection process during nodule organogenesis ─ occur simultaneously
Plant: attractants
Rhizobia: Nod factors
Cell wall degradation
Infection thread formation
Fuse with the membrane of root cell
Penetrate and new infection thread formation Branching and extending ba
cteria released into the cytosol
Bacteroids: a nitrogen-fixing endosymbiotic organelles (p. 301R)
The energetic of nutrient assimilation
¤ nitrate ammonium consumes ca. 25% of the total energy
less than 2% of the total dry weight produce
¤ occur in the stroma of the chloroplast
¤ Photoassimilation:
coupling nutrient assimilation to
photosynthetic e- transport
use the surplus reductants of
Calvin cycle
high light, low [CO2],
photoassimilation proceed
[CO2]
inhibit photoassimilation
inhibit photorespiration
C/N assimilation
C4 plants: photoassimilation occur in mesophyll cells, [CO2] low
High [CO2] in bundle sheath cells
Inhibit photoassimilation
Assimilatory quotient(AQ) CO2 assimilated / O2 evolved
as a function of light level
Wheat seedling
Photoassimilation
no photoassimilation
(no photoinhibition)
Photoassimilation:
CO2 fixation may interfere with nitrate photoassimilation
(1)
(1) NADH is supported by chloroplast via malate shuttle
(2) The level of reduced ferredoxin
(3) The acidification of stroma dissipate the pH gradient
CO2 itself and ATP regeneration
(2) stroma
(3)
WebEssay 12.1
The plants receiving NH4+ were
more responsive to CO2 enrichment than those receiving NO3
-
Doubling CO2 (enrichment):
short-term:
accelerate carbon fixation in C3 plants by about 30%
long-term (days to weeks):
carbon fixation declines until it stabilizes at a rate that averages
12% above ambient controls
CO2 acclimation
shoot N and proteins contents diminish
WebEssay 12.1
Sulfur assimilation
§ Sources:
The weathering of parent rock material
Industrial contamination, the burning of fossil fuels releases sulfur dioxide
and hydrogen sulfide
§ Absportion pathways:
sulfate: H+– SO42- symporter of the roots from the soil
sulfur dioxide take up from stomata
> 0.3 ppm, 8 h extensive tissue damage
§ Location
mostly in leaves which can supply reduced ferredoxin and serine (p. 305R)
§ The transported form in the phloem
glutathione (Gly-Cys--Glu), also acts as a signal that coordinates the absorption of sulfate by the roots and the assimilation of sulfate by the
shoot
Activated form
2
In plastids
In cytosol
gallic acid glucoside, glucosinolates, polysaccharides
(photorespiration)
Sulfur assimilation§ Functions:
The structural and regulatory roles in proteins, disulfide bridges
Electron transfer through iron-sulfur clusters
Catalytic sites for several enzymes and coenzymes
Secondary metabolites such as Nod factors, antiseptic
alliin in garlic, and anticarcinogen sulforaphane in
broccoli
Oxygen assimilation
¤ Respiration (major)
Photorespiration: rubisco oxygenase activity (major)
oxygen fixation (minor):
oxygen assimilated into organic compounds
¤ the types of oxygenases
dioxygenase:
monooxygenase: mixed-function oxidase
cell wall protein extensin, posttranslation
A + O2 + BH2 AO + H2O + B
hydroxylation
demethylation
In ER