The infection process during nodule organogenesis - occur simultaneously

1
The infection process during nodule organogenesis
- occur simultaneously
Plant attractants Rhizobia Nod factors
Fuse with the membrane of root cell
Cell wall degradation Infection thread formation
Penetrate and new infection thread formation
Branching and extending bacteria released into
the cytosol
Bacteroids a nitrogen-fixing endosymbiotic
organelles (p. 301R)
2
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

3
C4 plants photoassimilation occur in mesophyll
cells, CO2 low
High CO2 in bundle sheath cells ? Inhibit
photoassimilation
4
Assimilatory quotient(AQ) ? CO2 assimilated / O2
evolved as a function of light level
Wheat seedling
no photoassimilation
Photoassimilation ?
(no photoinhibition)
5
Photoassimilation
CO2 fixation may interfere with nitrate
photoassimilation
(3)
(1)
(2) stroma
(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
6
WebEssay 12.1 The plants
receiving NH4 were more responsive to CO2
enrichment than those receiving NO3
-
7
WebEssay 12.1
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
8
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
• gt0.3 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

9
gallic acid glucoside, glucosinolates,
polysaccharides
In cytosol
2
In plastids
Activated form
(photorespiration)
10
Cysteine ? Methionine(Web topic 12.3)
S-adenosylmethionine
11
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

12
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

13
In ER
cell wall protein extensin, posttranslation
hydroxylation demethylation
A O2 BH2 ? AO H2O B
14
Cation assimilation

• K, Mg, Ca, Cu, Fe, Mn, Co, Na, Zn
• coordination bonds and electrostatic bonds
• p. 306L

neutralization
oxalate