It's about the respiratory system of plants and breakdown of photosynthesis

1. RESPIRATORY SYSTEM
IN PLANTS

2. DO PLANTS BREATH?

3. 6CO2 + 6H2O → C6H12O6 + 6O2
RESPIRATION

4. • Plants breathe differently, through a process known as
CELLULAR RESPIRATION.
• Unlike humans and animals, plants do not possess any
specialized structures for exchange of gases, however,
they do possess stomata (found in leaves), lenticels
(found in stems) and root hairs actively involved in the
gaseous exchange. These respire at a low pace
compared to humans and animals.

5. • Aerobic
respiration
• Inhalation of O2
and exhalation of
CO2
• Provide energy
for their cells
• Respire through
stomata in leaves,
lenticels, and root
hairs
• Rate of respiration is
relatively much
slower
• Specialized
structures
(Lungs)
• Produced at
faster rate

6. LEAVES
• Consist of tiny pores known as
stomata.
• Gaseous exchange occurs
through diffusion via stomata.
• Guard cells regulate each of
the stomata. Exchange of
gases occurs with the closing
and opening of the stoma
between the inferior of leaves
and the atmosphere.
Guard Cells
Epidermal
Cells
Stoma
Chloroplast
Guard Cell
Wall
Nucleus
Epidermis of a
Leaf

7. STEMS
• They have pores on their
surface, called lenticels.
• Lenticels are openings on
the surface of stems and
roots through which oxygen,
carbon dioxide and water
can be exchanged with the
atmosphere.
Lenticels of Prunus serotina (Black
Cherry). Taken from
https://i0.wp.com/mgnv.org/wp-
content/uploads/2021/03/Lenticels_Prunus_serotina_Bark
_Sep_ELM.jpg?fit=768%2C1024&ssl=1

8. Lenticels on (A) Apple (B) Potato (C) Avocado
Pericarp (fruit covers) in plants, also have lenticels on their outer
surfaces for gaseous exchange.

9. STEMS
• They have pores on their
surface, called lenticels.
• Lenticels are openings on
the surface of stems and
roots through which oxygen,
carbon dioxide and water
can be exchanged with the
atmosphere.
Lenticels of Prunus serotina (Black
Cherry). Taken from
https://i0.wp.com/mgnv.org/wp-
content/uploads/2021/03/Lenticels_Prunus_serotina_Bark
_Sep_ELM.jpg?fit=768%2C1024&ssl=1

10. ROOTS
• Roots perform gaseous exchange directly with the help of root
hairs by diffusion through their cell membranes.
• Root hairs are fine hair-like cells that extend into the soil and maximize
root surface area for water absorption.
• It absorbs air from the air gaps/spaces found
between the soil particles. Hence, absorbed
oxygen through roots is utilized to liberate the
energy that in the future, is used to transport
salts and minerals from the soil.

11. CO2 + H20 C6H1206 + O2
PHOTOSYNTHESIS
RESPIRATION
ATP+

12. People are warn against
sleeping under a tree during
night time, as it may lead to
suffocation due to excess
amounts of carbon dioxide
liberated by trees following
respiration.

13. A breakdown of the processes used by
C3, C4, and CAM plants for
photosynthesis:

14. C3 Plants

15. 1. Carbon Fixation:CO2
enters the leaf through tiny
openings called stomata.
An enzyme called Rubisco
captures CO2 and
combines it with a 5-
carbon molecule called
RuBP to form a 6-carbon
molecule.
https://www.researchgate.net/figure/A
schematic-diagram-of-C3-and-C4-
photosynthesis_fig11_257881531

16. 2.Calvin Cycle: This 6-carbon
molecule is unstable and breaks
down through a series of reactions
to regenerate RuBP and produce a 3-
carbon sugar molecule
(glyceraldehyde-3-phosphate).
Energy from ATP and NADPH
(generated from sunlight in the light-
dependent reactions) is used to
power these reactions.

17. 3.Sugar Production: The
3-carbon sugar molecules
can be combined to form
larger sugar molecules
like glucose, sucrose, and
starch.

18. C4 Plants

19. 1.Mesophyll Cells:CO2 enters
the leaf through stomata and
is quickly captured by an
enzyme called PEP
carboxylase, combining with
a 3-carbon molecule (PEP) to
form a 4-carbon molecule
(oxaloacetate).

20. 2.Bundle Sheath Cells: The 4-
carbon molecule is transported to
specialized bundle sheath cells
surrounding the veins in the leaf.
3. Decarboxylation: The 4-carbon
molecule releases CO2, which is
concentrated around Rubisco in
the bundle sheath cells.

21. 4. Calvin Cycle: Rubisco
efficiently captures the
concentrated CO2 and
incorporates it into the Calvin
cycle as in C3 plants, producing
sugars.
5. PEP Regeneration: The
remaining 3-carbon molecule
from the 4-carbon compound is
transported back to the
mesophyll cells and converted
back into PEP using energy from
ATP

22. CAM Plants

23. 1. Nighttime: Stomata open at
night to allow CO2 to enter the
leaf. CO2 is captured by an
enzyme and converted into
organic acids, which are stored
in the plant.
2. Daytime: Stomata close during
the day to conserve water. The
organic acids are broken down,
releasing CO2 into the
chloroplasts
https://www.khanacademy.org/scienc
e/biology/photosynthesis-in-
plants/photorespiration--c3-c4-cam-
plants/a/c3-c4-and-cam-plants-
agriculture

24. 3. Calvin Cycle:
Rubisco captures the
released CO2 and
incorporates it into
the Calvin cycle as in
C3 plants, producing
sugars.
https://www.khanacademy.org/scie
nce/biology/photosynthesis-in-
plants/photorespiration--c3-c4-
cam-plants/a/c3-c4-and-cam-plan

25. C3
CAM
C4
Photosynthesis
Sunlight
Calvin cycle
• Fix carbon during the day
• Fix carbon dioxide in
mesophyll
• Less efficient in hot and
dry conditions
• Fix carbon during the day
• Fix carbon dioxide in
mesophyll, then bundle
the sheath cells
• More efficient in hot and
dry conditions
• Fix carbon during the day
• Fix carbon dioxide in
mesophyll, then bundle
the sheath cells
• More efficient in hot and
dry conditions
• Fix carbon mainly at night
• Fix carbon dioxide in mesophyll
then store vacuoles
• Highly efficient in hot and dry
conditions