IGCSE Plant Nutrition

1. Plant Nutrition
B M Subramanya Swamy M.Sc. B.Ed.
CIE Co ordinator & Examination Officer
Kanaan Global School
Jakarta
Indonesia
subramanyaswamy1591978@gmail.com

2. Plant nutrition
• Introduction
• Photosynthesis
• Leaf structure
• Mineral nutrition

3. Introduction
• Autotrophs :organisms that can synthesize their
organic material from inorganic material in the
environment they are called producer
• They include all green plants and some bacteria
• Chemosynthetic Autotrophs utilize chemical energy
instead of light energy to synthesize their organic
materials
• Heterotrophs they do not make their own food they
obtain carbon and energy from organic materials
already produced by autotrophs
• They include animals and fungi
• They are called consumers

4. Photosynthesis
• Maintain 0.03% of carbon di oxide in the air
• When carbon dioxide is trapped in the air
there is a global increase in co2 levels
• Green plants help to reduce carbon di oxide in the air
during photosynthesis

5. • Light energy is used by green plants to synthesise
organic compounds such as sugars from inorganic
compounds like water and carbon di oxide
• Photosynthesis is a process by which light energy
from sun is converted into chemical energy. Carbon
di oxide and water react using sunlight absorbed by
chlorophyll to produce glucose and oxygen

6. Chlorophyll
• Most abundant
photosynthetic pigment in
plants
• Located mainly in the
chloroplast
• Consists of chlorophyll a & b
both absorbs blue and red
light
• Chlorophyll a is the primary
pigment for photosynthesis

7. Comparison of light and dark reaction
Light reaction Dark reaction
Occurs in chloroplast Occurs in chloroplasts but not
chlorophyll
Sunlight activates chlorophyll and
activated chlorophyll splits water
(photolysis) into hydrogen ions and
oxygen and energy
Hydrogen ions combines with oxygen
and energy to form glucose
There is a conversion of light energy into
chemical energy
The reaction involves enzymes and is
temperature dependent

8. Light reaction cyclic photophosphorylation

9. LIGHT ABSORBTION
AND TRANSFER
TO THE REACTION
CENTERS

10. NADP reductase
O2 + 4H+
2H2O
2H+ + 2NADP
NADPH
4 e-
4 photons
4 photons
2 H+
CYT B6f
PC
PSI
PSII
Fd
The Path of Electron and Proton Flow in Photosynthetic Electron
Transport
PQ

11. Under conditions where NADP+ regeneration is slow, or ATP
demand is high, the leaf can cycle electrons between
plastoquinone and PSI, and in doin so pump protons across
the membrane. This is termed cyclic photophosphrylation.
NADP reductase
2 H+
CYT B6f
4 H+
PC PSI
PSII
PQ
Fd
CYCLIC PHOTOPHOSPHORYLATION

12. PHOTOPHOSPHORYLATION
Chloroplast stroma – region of high pH
PHOTOSYSTEM I
ATP Synthase
(F-type ATPase)
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+ H+
H+
H+
H+
H+
H+
H+
H+ H+
H+
H+
H+
H+
ADP
H+ ATP
+ Pi
3 H+
Thylakoid Lumen – compartment of low pH

14. Phase 1: Carboxylation
RuBP (5 carbon) + CO2 RUBISCO 2 PGA (3 carbon)
Note: The oxygen in
CO2 is incorporated
into one of the PGA
molecules. It is not
released as O2.

15. Properties of Rubisco
(Ribulose-1,5-bisphosphate carboxylase/oxygenase)
In primitive photosynthetic
bacteria, Rubisco exists as a
dimer of two subunits
In the evolution of the blue-green
algae, the primitive, two-subunit
form of Rubisco was
modified by the combination of
4 dimers to give a complex of 8
subunits in four pairs of dimers.

16. RuBP Oxygenation
RuBP (5 carbon) + O2 RUBISCO PGA + PG

17. Summary of photosynthesis

18. External view of leaf
Lamina Flat thin broad
Large surface area for absorption of sunlight
Stomata found on the lower surface
Veins Good water supply throughout the leaf

19. Internal structure of a leaf

20. Epidermis •Single layer of cells
•Outer wall of cells covered with cutin
•No chloroplast
Cutin •Waxy substance
•Impervious to water and gases
Stomata •Kidney shaped cells
•Only on lower epidermis

21. Mesophyll
palisade cells
•Between upper and lower epidermis
•1-2 layer of closely packed cells
•Large number of chloroplast
Spongy
Mesophyll
•Loosely arranged
•Irregular cell
•Large intercellular space
•Facilitates diffusion of gasses
•Has chloroplasts

22. Vascular tissue •Forms main vein and branch veins of lamina
Xylem •Conducts and distributes water and mineral salts
Phloem •Carries products of photosynthesis to other parts of
plant
Vascular bundle •Surrounded by a layer of cells forming the bundle
sheath

23. Chloroplast •Arrangement in palisade cells
to absorb maximum amount of
sunlight
•More found in palisade cells
than in the spongy mesophyll
cells

24. Stomata •Works together with the mesophyll cells for efficient gaseous
exchange
•Carbon dioxide enters and oxygen leaves
•Controlled by opening and closing of stomata
Opens (day) •Photosynthesis produces sugar
•This create a concentration gradient causing osmosis of water
into the guard cells
•Cells balloon up pores open
Close (night) •Sugar is converted to starch
•Water is lost to neighboring cells
•Guard cells become flaccid pores closes
•This reduces intake of carbon dioxide by leaf
•Photosynthesis reduces and then stops
•Hydrolysis of starch begins

25. Factor affecting photosynthesis
Carbon dioxide Temperature Light
Carbon dioxide in air is
about 0.03% and does not
vary much
In the dark stage
photosynthesis is enzyme
controlled
Increase light intensity
increase rate of
photosynthesis
Increase in carbon dioxide
increase rate of
photosynthesis
Increase temperature to 40
C decrease the rate of
photosynthesis as enzyme
action is greatly reduced
Up to saturation point
Further increase in light
has no effect
Increase only up to carbon
dioxide saturation point
Temperature greater than
40 c enzymes are
denatured and
photosynthesis stops
Absence of light no
photosynthesis only
respiration

26. ----------- ------------------
-----
As light intensity increases carbon
dioxide from respiration is equal to
carbon dioxide absorbed for
photosynthesis
-------- ------------------
----
As light intensity increase increases
further net releases of carbon dioxide
and uptake of carbon dioxide leads to an
increase in the amount of sugar in the
plant
------------
--
------------------
------
At very high light intensity
photosynthesis slows down
as UV damages chlorophyll

27. Mineral Nutrition
• Macronutrient – chemical elements needed in
rather larger amounts
• E.g nitrogen, phosphorous, sulpur, magneium,
potassium & calcium
• Micronutrient – traces elements needed in
tiny amounts
• E.g. manganese, cobalt, zinc, copper,
molybdeum

28. Element Function Deficiency symptom
Nitrogen Component of chlorophyll amino
acids & protien
Stunted growth
Chlorosis of leaves
Phosphorous For release of energy Stunted growth
Dull green leaves
Leaves with curly brown edges
Sulphur Component of protein and amino
acids
Chlorosis of leaves
Weak stem
Magnesium Component of chlorophyll Chlorosis of leaves
Death of leaf or portion of it
Potassium For increase hardness Chlorosis of leaves
Dead tissue tips and edges of leaves
Calcium Cells formation at root and shoot
tips
Stunted growth
Poor buds
New leaves distorted in shape