Plant Physiology-C4-pathway-CAMpathway ||.. By UK sir
Photo Synthesis - 2
 |
| Flowering plant |
C4 Pathway: (Hatch- slack pathway)
•
Special
type of pathway where 1st stable product of reaction is 4 carbons (OAA).
•
Hatch
& slack in 1966 discovered this pathway.
•
Also
called HSK Cycle (Hatch Slack and Kortschak Cycle)
•
The
plant where C4 cycle occurs called as C4 plants. ( sugar cane,
maize, sorghum. )
•
Special
anatomy present called as Kranz anatomy.
•
Bundle
sheath cell don't contain grana whereas mesophyll cell chloroplast contain grana.
Want to Know about Cellular Respiration:
https://uksirnotes.blogspot.com/2021/05/plant-physiology-respiration-by-uk-sir.html
Want to Know about Phyto Hormones:
Mechanism
 |
| C4-Pathway |
In Mesophyll Cell :
CO2 accepted by PEP of mesophyll cell by the help
of enzyme PEPCO.
PEP + CO2 + H2O ------------PEPCO----------à OAA (4C) + H3PO4
OAA + NADPH2 -------------Dehydrogenase-----à Malic Acid + NADP+
OAA + Alanine --------------Transaminase------à Aspartic Acid + Pyruvic Acid
In Bundle sheath Cell :
Malic acid + NADP+ ------------Malic Enzyme -----à Pyruvic Acid + NADPH2 + CO2 CO2 accepted by RuBP in BSC and
again utilized in C3 cycle.
Regeneration of PEP :
Pyruvic Acid + ATP + H3PO4----------Phosphate
Dikinase--à
PEP + AMP +PPi
For 1 molecule of Glucose = 30 ATP and 12 NADHPH2
require.
Significance:
·
C4
plants Can fix more amount of CO2
·
They
show More adaptation to environmental stress
·
They
are more adapted to Saline soil.
·
They
Require more ATP for fixation
CAM – Pathway:
-
1st
time reported by Ting 1971.
-
Crassulacean
Acid Metabolism occurs in most of the member of Crassulaceae family.
-
Some
plants like- Opuntia, Pine apple, Sedum etc.
-
Contain
Scotoactive stomata.
-
Same
cell contain both PEP and RuBP.
Mechanism:
CAM Pathway
During Night time : (Stomata Open)
Stored Sugar of Chloroplast ---à Sugar Phosphate
--à Pyruvate
-----à Phosphoenol pyruvate
---à PEP
accept atmospheric CO2 ---à OAA
PEP + CO2 ------PEPCO----à OAA
OAA + NADPH2 ----------Dehydrogenase------------à Malic Acid + NADP+
•
Malic Acid is stored inside Vacuole in night time.(Acidification)
During Day Time: (Stomata Close)
-
Malic Acid store in Vacuole ---------à Malate (De acidification starts)
-
Malate + NADP+------------Malic enzyme-----------à Pyruvate + CO2 + NADPH2
-
CO2 is again used in C3
cycle.
-
Pyruvate again regenerate the PEP for acceptance of
CO2
Ecological Significance:
-
Scotoactive stomata prevent water loss.
-
Large amount of malic acid is stored in vacuole.
-
CAM plants are water efficient and adapted to hot
climate.
-
Growth rate is low as the real photosynthesis lack
during day time.
Photo Respiration/ C2 Cycle/ Glycolate Cycle :
-
Different process then the photosynthesis.
(Respiration like process in presence of Light)
-
Due to high temp and 0xygen conc., RuBisCO starts
accepting Oxygen.
-
It’s just opposite of C3 Cycle as it
produces CO2
-
Occurs in Temperate plants like wheat, rice,
Barley, beans etc.
-
Here 3 organelles are included (Chloroplast, Peroxisome
and Mitochondria)
Mechanism:
C2-Cycle
-
1st
RuBP accept O2 due to RuBiscO Enzyme and form PGA and PhosphoGlycolate
(2C)
 |
| Reaction 1 |
-
PhosphoGlycolate
will form Glycolate which is transported to Peroxisome.
-
Glycolate
eventually convert to Glyoxylate and finally Glycine addition to amino group.
-
Now
Glycine transport to Mitochondria.
-
Here
Glycine convert to Serine by releasing CO2
Reaction2
-
Again
Serine come back to Peroxisome converting to Hydroxypyruvate and finally to Glycerate.
 |
| Reaction3 |
-
Glycerate
transfer to Chloroplast and form RuBP.
Ecological Significance:
-
It’s
a harmful process, as no energy is produced and release of a fixed Caron.
-
It
consumes energy.
-
Loss
of fixed Carbon.
-
Sometime
protect the plant from photo oxidative damage.
Want to Know about Cellular Respiration:
https://uksirnotes.blogspot.com/2021/05/plant-physiology-respiration-by-uk-sir.html
Want to Know about Phyto Hormones:
***
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