This presentation provides an overview of C4 plants and the Hatch-Slack or C4 cycle of carbon fixation. It begins with defining C4 plants as those that have Kranz anatomy and the first stable compound of photosynthesis is a four-carbon compound called oxaloacetic acid. The presentation then describes the key features of Kranz anatomy and the two cycles - the C4 cycle in mesophyll cells and C3 cycle in bundle sheath cells. It provides details on the steps of the C4 cycle and pathways of carbon fixation. The presentation concludes by comparing the differences between C3 and C4 plants as well as differences between the C3 and C4 cycles of carbon fixation.

1. WELCOME
TO ALL OF YOU
FOR TADAY’S PRESENTATION
BACHELORS OF 3RD YEAR
SUBJECT : BOTANY
TOPIC : HATCH AND SLACK CYCLE OR C4 CYCLE
OR CARBON FIXATION IN C4 PLANTS
CREATED AND PRESENTED BY : ATIF ALI ZAKIR

2. WHAT ARE C4 PLANTS
 C4 PLANTS ARE THOSE PLANTS IN WHICH THE FIRST STABLE
COMPOUND OF PHOTOSYNTHESIS IS FOUR CARBON COMPOUND
CALLED AS OXALO ACETIC ACID
 THE LEAVES OF THESE PLANTS SHOW KRANZ ANATOMY, THEY
HAVE CHLOROPLASTS IN THE BUNDLE SHEATH CELLS
 IN KRANZ ANATOMY THE VASCULAR BUNDLE ARE SURRONDED
BY A LAYER OF BUNDLE SHEATH CELLS ,THESE B.S.Cs ARE
SURROUNDED BY ONE OR MORE LAYERS OF MESOPHYLL CELLS
 THERE ARE TWO CO2 ACCEPTORS IN THE FORM OF RUBP & PEP
 THESE PLANTS INVOLVE BOTH C3 & C4 CYCLES
 C3 CYCLE TAKE PLACE IN BUNDLE SHEATH CELLS & C4 CYCLE IN
MESOPHYLL CELLS
 EXAMPLES, SUGAR CANE, MAIZE, AMARANTHUS, SORGHUM,
CYPRUS etc.

3. KRAN’Z ANATOMY

4. C4 CYCLE
 PHOSPHO ENOL PYRUVIC ACID PRESENT IN THE MESOPHYLL CELLS ABSORBS CO2
 THIS RESULT IN THE FORMATION OF (4-C compound) OXALO ACETIC ACID IN THE
PRESENCE OF ENZYME PEP-CARBOXYLASE
 OAA IS THEN CONVERTED INTO EITHER MALIC ACID OR ASPARTIC ACID
 OAA IS REDUCED TO MALIC ACID BY NADPH2 IN THE PRESENCE OF ENZYME MALATE
DEHYDROGENASE
 MALIC ACID IS THEN TRANSPORTED TO BUNDLE SHEATH CELLS, SURROUNDING THE
VASCULAR BUNDLE
 DECARBOXYLATION OF MALIC ACID TO FORM PYRUVIC ACID AND CO2
 CO2 CONCENTRATION INCREASE IN BUNDLE SHEATH CELLS
 B.S.Cs HAVE C3-CLYCLE ENZYME i.e., RUBISCO PARTICIPATES IN THE CALVIN CYCLE AND IN
PHOTORESPIRATION
 THE RELEASED CO2 COMBINES WITH (RUBP) RIBULOSE BISPHOSPHATE (2ndry Acceptor
Of CO2)
 THEN ENTERS IN THE CALVIN CYCLE FOR THE FORMATION OF CARBOHYDRATES
 PYRUVIC ACID GENERATED IN THE B.S.Cs IS TRANSPORT BACK TO MESOPHYLL CELLS
 HERE IT IS CONVERTED TO PHOSPHOENOL PYRUVIC ACID (Primary Acceptor) IN THE
UTILIZATION OF AN ATP MOLECULE

5. PATHWAY OF C4 CYCLE

6. DIFFERENCE BETWEEN C3 & C4 PLANTS
C3 PLANTS
 LEAVES DONOT SHOWS KRANZ
ANATOMY
 BUNDLE SHEATH CELLS DONOT
POSSES CHLOROPLASTS
 CHLOROPLASTS ARE
MONOMORPHIC
 THEY OPPERATE ONLY CALVIN CYCLE
OR C3 CYCLE WHICH OCCURS IN M.C
 THERE IS ONLY ONE CO2 ACCEPTOR
i.e., RUBP
 THEY ARE LESS EFFICIENT IN
UTILIZATION OF CO2
 THEY NORMALLY SHOWS PHOTO-
RESPIRATION
 FIRST STABLE COMPOUND OF
PHOTOSYNSTHESIS IS 3-CARBON
CALLED PHOSPHOGLYCERIC ACID
 DUE TO PHOTO-RESPIRATION THERE
IS REDUCTION IN PHOTOSYNTHETIC
YEILD
C4 PLANTS
 LEAVES SHOWS THE KRANZ ANATOMY
 BUNDLE SHEATH CELLS POSSES LARGE
CHLOROPLASTS
 CHLOROPLASTS ARE DIMORPHIC i.e.,
MESOPHYLL CELLS HAVE NORMAL TYPE
,B.S.CELLS HAVE LARGE SIZE
 THEY OPPERATE WITH C4 CYCLE OCCURS IN
(M.C.C )AND CALVIN CYCLE OR C3 CYCLE
WHICH OCCURS IN (B.S.C)
 THERE IS TWO CO2 ACCEPTOR i.e., RUBP &
PEP
 THEY ARE MUCH MORE EFFICIENT IN
UTILIZATION OF CO2
 PHOTORESPIRATION IS ABSENT OR
INSIGNIFICANT
 FIRST STABLE COMPOUND OF
PHOTOSYNSTHESIS IS 4-CARBON CALLED
OXALO ACETIC ACID
 DUE TO ABSENCE OF PHOTO-
RESPIRATION,THE EFFICIENCY OF
PHOTOSYNTHESIS IS FURTHER INCREASED

7. DIFFERENCE BETWEEN C3 & C4 CYCLE
CALVIN CYCLE (C3 CYCLE)
 THE PRIMARY ACCEPTOR OF CO2
IS RIBULOSE BIPHOSPHATE
(RUBP), 5 CARBON COMPOUND
 THERE IS NO SECONDARY
ACCEPTOR OF CO2
 THE FIRST STABLE COMPOUND
FORMED DURING
PHOTOSYNTHESIS IS A 3-
CARBON COMPOUND CALLED 3-
PHOSPHOGLYCERIC ACID
 CO2 ONCE FIXED BY (RUBP) IS
NOT RELEASED BACK
 THERE IS NET GAIN OF ONE
HEXOSE SUGAR FOR EVERY 6
MOLECULES OF CO2 FIXED
 IT HAS SLOWER RATE OF CO2
FIXATION
 IT OCCURS IN ALL PLANTS
HATCH-SLACK CYCLE (C4 CYCLE)
 THE PRIMARY ACCEPTOR OF CO2
IS PHOSPHOENOL PYRUVIC ACID
(PEP), 3 CARBON COMPOUND
 THE SECONDARY ACCEPTOR OF
CO2 (RUBP)
 THE FIRST STABLE COMPOUND
FORMED DURING
PHOTOSYNTHESIS IS A 4-
CARBON COMPOUND CALLED
OXALO ACETIC ACID
 FIXED CO2 IS RELEASED BACK TO
B.S.C. WHERE IT IS FINALLY FIXED
BY (RUBP) SECONDARY CO2
ACCEPTOR
 THERE IS NO SUCH GAIN BUT
MALIC ACID IS FORMED
 IT HAS FASTER RATE OF CO2
FIXATION
 IT OCCURS ONLY IN C4 PLANTS

8. THANK YOU SO MUCH
FOR
ATTENDING TODAY’S
PRESENTATION
CREATED AND PRESENTED BY
ATIF ALI ZAKIR
STUDENT OF MSC BOTANY II YEAR
SAIFIA SCIENCE COLLEGE BHOPAL