Photosynthesis

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Photosynthesis

• What is it ?
• Where it occurs ?
• How ?
• How is its important ?
• How to measure ?

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Photosynthesis ?????????? 3 ?????????????

• CO2 diffusion
• A Cg dCO2
• Photochemical process (light reaction)
• 4H2O 2ADP2NADP 2pi
  O22H2O2ATP2NADPH 2H
• Biochemical process
• 3CO29ATP6NADPH6H
  triose-P6NADP9ADP8Pi3H2O

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The overall chemical reaction

• CO2 2H2O (CH2O) H2O O2

H2O light / atenna O2
H Pi
ADP Pi NADP PSII PSI Cytochrome ATP NADPH
CO2 enzymes/ stroma
(CH2O) RuBPcarboxylase CO2receptor
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CHLOROPLAST

• 1- 10 mm
• Lamellae (membranes) light reaction
• stroma lamella (double lamella)
• grana lamella (stacked lamella)
• Stroma dark reaction

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Leaf anatomy of C3 vs. C4 plants
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Chloroplast and Chlorophyll structure
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Electron transportation

• Chlorophyll a ,b Carotenoid
• Reaction centers absorbed PHOTONS from light
  energy
• PSII ground stage excited
  stage
• PSI Q , Photophosphorylation

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Energy diagram of the photosynthetic electron
transport system
Light
Light
Chlorophyll a
Chlorophyll a/b
P700
P680
Electron transfer
O2
Electron transfer
NADPH
ATP
H2O
Photosystem I
Photosystem II
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Energy diagram of the photosynthetic electron
transport
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Radiation vs Photons

• E hv speed of light/wave length
• E energy content of the quantum (J/quantum)
• h Planck s constant (6.626 x 10-34 J s)
• 400 500 600 700 (nm)
• 25 20 16.7 14.3 (x103 cm-1)
• 7.5 6 5 4.5 (x1014
  s-1)
• 5 4 3.3 2.9 (x10-19 J
  quantum-1)

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Conversion factors for energy units used in the
text

• 1 electron volt (eV) 1.602 x 10-19 J
• 1 watt 1 J s-1
• 1 kWh 3.6 x 106 J
• 1 Joule 0.239 calories
• 6.242
  x 1018 eV
• 1 cal. 4.184 J
• 1 kJ mol quantum -1 1.036 x 10-2 eV
• Planks constant 6.62 x 10-34 Js
• 4.136 x 10-15 eVs
• 1 mol quantum of photon contains Avogadros
  number 6.023 x 1023 particles 1 Eistein

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Radiation Light
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Carbondioxide fixation

• Biomass or Dry weight Photosynthesis -
  Respiration - Dead - Translocation
• Carbon Balance
• C3 species Calvin cycle RUBP 3-PGA
• C4 species Hatch Slack cycle PEP
  Oxaloacetic Acid etc.
• Crussulation Acid Metabolism (CAM) CO2 fixed
  during night
• C3 vs C4 Kranz anatomy

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C3 C4 and CAM plant
PEP Carboxylase
RuBP Carboxylase
CO2
CO2
C4 Organic acids
CO2
PGA
(CH2O)
RUBP
PEP
C3 acids
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??? C3 vs C4

• ?????????????????????? C3 ?????Vascular sheath
  ??? C4 ?? (Kranz anatomy)
• ??????? PEPase ??????????????? CO2 ?????? ???????
  RUBPase
• C4 ?????????????????????????????? C3
  (????????????)
• C4 ????????????????? C3 ????????? CO2 1 ???????
• C4 ?? RUBP ???????? C3
• C3 ?????????????????? ???????? ??? ????????
  ???? C4 ?????????????????? ???? ???? ???? ????
• C3 ?? Photorespiration ???? C4 ?????

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Cellular respiration

• The process by which active cells obtain energy.
  It occurs in mitochondria, there are two
  coditions aerobic anaerobic respiration.
• The obtained energy was used for maintenance and
  growth of the cell or organ.
• Growth respiration catabolism provides the
  energy required for biosynthesis and constructive
  reactions leading to form cellular products used
  in the crop growth

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Aerobic respiration has 3 stages

• C6H12O6 6O2 6CO2 6H2O energy

Sucrose
NAD
O2
e transport chain Oxidative phosphorylation
Pyruvic acid
TCA Krebs cycle
Glycolysis
H2O
NADH
NADH, ADP
NADH, ATP
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Respiration

• MITOCHONDRIA
• C6H12O6 6O2 6CO2 6H2O 637
  kcal
• Glycolysis anaerobic respiration
• aerobic respiration Krebs cycle Oxidative
  phosphorylation

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Major plant metabolisms

• STRUCTURAL compounds
• cellulose
• hemicellulose
• pentosans
• pectin, ect.

• STORAGE compounds
• starch
• fructosans
• proteins
• lipids, ect.

• ACTIVE CELL compounds
• nucleic acids
• enzymes
• cytochrome
• chlorophyll
• phospholipids, ect.

O2
Chloroplast Photosynthesis
Synthesis / Translocation
Glycolysis
ATP, NADP
CO2
Mitochondria Respiration Krebs cycle
CO2
O2
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Photosynthesis vs Respiration

• Photophosporylation
• NADPH formed
• CO2 reduction
• CO2 as substrate
• H2O as substrate
• O2 is product
• CH2O is product

• Oxidative phosphorylation
• NADP formed
• O2 reduction
• CO2 is product
• H2O is product
• O2 is substrate
• (CH2O)n is substrate and product

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Photosynthesis vs Respiration if .

• Down
• Up
• Up
• Up
• Stop

• Up if O2
• Down if CO2
• Up if light
• Up if temperature
• Burst if dark

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Environments SOIL CLIMATE AGRONOMY
Character of CROPS
Water route
Photosynthesis
Yield potential
Etr/Etm
Pst
P pot X HI
Pst Etr/Etm -Res
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BAMnut model (Azam-Ali Sayed et.al, 2001. A
Global Mapping Systems for Bambara Groundnut
Production. FAO Agricultural Information
Management Series)
Weather data
Water limited growth (WLG)
Radiation limited growth (LLG)
seed
Intercepted radiation
Bambara groundnut
Water uptake
Leaf
Soil water
PodW
Root
LeafW
RootW
ShootW