PLANT
NUTRITION
Darrell Christian
Photosynthesis
An anabolic, endergonic, Carbon dioxide (CO₂) requiring process
that use light energy (Photons) and Water (H₂O) to produce
macromolecules (Glucose / C₆H₁₂O₆) for the energy of plants
Anabolic process: Generation of complex molecules
from simple molecules using energy.
Endergonic reaction: A reaction that requires energy to
be absorbed in order to kickstart a chemical reaction
Endothermic reaction: Sunlight energy is absorbed by
green plants during this process.
6CO₂ + 6H₂O - (Light Energy/Chlorophyll) -> C₆H₁₂O₆ + 6O₂
Photosynthesis
6CO₂ + 6H₂O - (Light Energy/Chlorophyll) -> C₆H₁₂O₆ + 6O₂
PROCESS OF
Photosynthesis
1. Water (H₂O) is absorbed from the soil by the roots.
Carried in the water vessels of the veins, xylem, up the
stem to the leaves.
2. Carbon Dioxide (CO₂) is absorbed from the air through
the stomata (Pores in the leaf).
3. In the leaf cells, the Carbon Dioxide (CO₂) and water
(H₂O) are joined to make sugar (C₆H₁₂O₆); where the
energy comes from sunlight which has been absorbed by
the green pigment chlorophyll in the chloroplasts of the
leaf cells.
PROCESS OF
Photosynthesis
4. Chlorophyll absorbs energy from light and uses it to
split water (H₂O) molecules into Hydrogen (H₂) and
Oxygen (O₂).
5. The Oxygen (O₂) escapes from the leaf through the
Stomata. While the Hydrogen (H₂) molecules join with
Carbon Dioxide (CO₂) molecules to make sugar
(C₆H₁₂O₆).
2 STAGES OF
Photosynthesis
Light-dependent
Reactions
They require light to take place.
These reactions occur in the
thylakoid membranes of the
chloroplast.
Light energy is absorbed by
chlorophyll, which leads to the
creation of ATP (adenosine
triphosphate) and NADPH
(nicotinamide adenine
dinucleotide phosphate).
Light-independent
Reactions
They do not directly require light
but depend on the products (ATP
and NADPH) generated in the lightdependent reactions.
These reactions occur in the
stroma of the chloroplast.
“fix” carbon from carbon dioxide
into molecules that can be used to
form glucose.
NADP
NADP
NADP (Nicotinamide Adenine
Dinucleotide Phosphate) is an electron
carrier in its oxidized form.
In the light-dependent reactions of
photosynthesis, chlorophyll absorbs
light energy, leading to the excitation
of electrons.
These excited electrons are transferred
through a series of proteins in the
thylakoid membrane, known as the
electron transport chain.
NADP accepts these high-energy
electrons at the end of the electron
transport chain, becoming reduced to
NADPH.
NADP
NADP (Nicotinamide Adenine
Dinucleotide Phosphate) is an electron
carrier in its oxidized form.
In the light-dependent reactions of
photosynthesis, chlorophyll absorbs
light energy, leading to the excitation
of electrons.
These excited electrons are transferred
through a series of proteins in the
thylakoid membrane, known as the
electron transport chain.
NADP accepts these high-energy
electrons at the end of the electron
transport chain, becoming reduced to
NADPH.
NADP
NADP (Nicotinamide Adenine
Dinucleotide Phosphate) is an electron
carrier in its oxidized form.
In the light-dependent reactions of
photosynthesis, chlorophyll absorbs
light energy, leading to the excitation
of electrons.
These excited electrons are transferred
through a series of proteins in the
thylakoid membrane, known as the
electron transport chain.
NADP accepts these high-energy
electrons at the end of the electron
transport chain, becoming reduced to
NADPH.
NADP
NADP (Nicotinamide Adenine
Dinucleotide Phosphate) is an electron
carrier in its oxidized form.
In the light-dependent reactions of
photosynthesis, chlorophyll absorbs
light energy, leading to the excitation
of electrons.
These excited electrons are transferred
through a series of proteins in the
thylakoid membrane, known as the
electron transport chain.
NADP accepts these high-energy
electrons at the end of the electron
transport chain, becoming reduced to
NADPH.
NADPH
NADPH is the reduced form of NADP,
meaning it has accepted electrons
during the light-dependent reactions.
It acts as a carrier of high-energy
electrons and protons (H+) that are
used in the light-independent
reactions of photosynthesis.
In the Calvin cycle, NADPH provides the
necessary reducing power to convert
carbon dioxide into glucose and other
carbohydrates.
The electrons and protons carried by
NADPH are used to reduce carbon
dioxide and convert it into sugars
through a series of enzymatic
reactions.
NADPH
NADPH is the reduced form of NADP,
meaning it has accepted electrons
during the light-dependent reactions.
It acts as a carrier of high-energy
electrons and protons (H+) that are
used in the light-independent
reactions of photosynthesis.
In the Calvin cycle, NADPH provides the
necessary reducing power to convert
carbon dioxide into glucose and other
carbohydrates.
The electrons and protons carried by
NADPH are used to reduce carbon
dioxide and convert it into sugars
through a series of enzymatic
reactions.
other kitchen = calvin cycle
Where does it take place?
Leaf structure &
All green parts of
the plants
Leaf Structure
Chloroplast
Leaf Structure
Where does it take place?
Leaf structure &
All green parts of
the plants
Lamina: The broad, flat part of the
leaf that maximizes the surface
area exposed to sunlight. It is the
primary site for photosynthesis.
Leaf Structure
Chloroplasts
Leaf Structure
Where does it take place?
Leaf structure &
All green parts of
the plants
Petiole: The stalk that attaches
the leaf blade to the stem. It
provides support and allows the
leaf to be positioned for maximum
exposure to sunlight.
Leaf Structure
Chloroplasts
Leaf Structure
Where does it take place?
Leaf structure &
All green parts of
the plants
Veins: Vascular bundles within the
leaf that transport water, nutrients,
and sugars. Veins also provide
structural support for the leaf.
Leaf Structure
Chloroplasts
Leaf Structure
Where does it take place?
Leaf structure &
All green parts of
the plants
Midrib: The central vein running
along the middle of the leaf. It
contains the main vascular
bundle and provides support.
Leaf Structure
Chloroplasts
Leaf Structure
Where does it take place?
Leaf structure &
All green parts of
the plants
Margins (Leaf Edges): The outer
edges of the leaf blade. The
margins increase the surface area
for gas exchange and light
absorption.
Leaf Structure
Chloroplasts
Where does it take place?
Leaf structure &
All green parts of
the plants
Leaf Structure
Chloroplast
CHLOROPLAST
1. Inner membrane: Surrounds the internal
space of the chloroplast and is selectively
permeable. (Controlling movement)
CHLOROPLAST
2. Intermembrane space: The space
between the outer and inner membranes.
CHLOROPLAST
3. Outer membrane: Defines the outer
boundary of the chloroplast and regulates
the passage of ions and molecules.
CHLOROPLAST
4. Stroma: Contains enzymes and
substrates necessary for the synthesis of
carbohydrates.
(Fluid filled region where Lightindependent reactions take place)
CHLOROPLAST
5. Thylakoid: Thylakoid membranes
contain pigments, that capture light
energy.
(Flatted disc-like structures where light
dependent reactions take place)
CHLOROPLAST
Granum (Plural: Grana): Stacks of
thylakoid membranes.
6. Lamella: It connects thylakoids of two
different grana.
(They increase the efficiency of
photosynthesis by keeping grana at a
distance so that they do not clutter
together.)
PARTS OF THE LEAF
Cuticle: A waxy, waterproof layer covering the leaf surface. It
helps reduce water loss through evaporation (transpiration)
and protects against pathogens.
PARTS OF THE LEAF
Upper epidermis: A protective layer, providing a barrier against
pathogens and environmental stresses while allowing light to
penetrate for photosynthesis.
PARTS OF THE LEAF
Palisade Mesophyll: The main site of photosynthesis,
containing closely packed, vertically oriented cells that
maximize light absorption.
PARTS OF THE LEAF
Spongy mesophyll: A layer of loosely arranged cells beneath
the palisade mesophyll that facilitates gas exchange and the
movement of nutrients.
PARTS OF THE LEAF
Lower epidermis: A protective layer containing stomata,
regulating gas exchange and water vapor release while
helping to prevent excessive water loss through transpiration.
PARTS OF THE LEAF
Stoma (plural: Stomata): Small pores on the leaf surface,
primarily on the underside, allowing for the exchange of gases
(oxygen and carbon dioxide) and regulating water vapor loss
during transpiration.
Experiments
for photosynthesis
1. Is chlorophyll necesarry for photosynthesis
Results:
Only the parts that had chlorophyll in them turn
blue with iodine. The parts that were white stain
brown
Interpretation:
Starch is only present in the parts that contained
chlorophyll, so this suggests that chlorophyll is
needed for photosynthesis.
However, there are other possible explanations
which this experiment has not ruled out. For
example, starch could be made in the green
2. Is light necessary for photosynthesis?
Result:
Only the areas that had received light go blue
with iodine
Interpretation:
Starch has not formed in the areas that received
no light, so light is needed for starch formation.
and therefore light is needed for photosynthesis.
It is possible that the aluminium foil had
stopped carbon dioxide from entering the leaf,
and so it was a shortage of carbon dioxide
rather than a shortage of light that stopped
photosynthesis happening. Another control
could be designed. using transparent material
instead of aluminium foil for the stencil.
3. Is carbon dioxide needed for photosynthesis?
Result:
The leaf that had no carbon dioxide does not
turn blue. The one with carbon dioxide does
turn blue.
Interpretation:
Starch was made in the leaves that had
carbon dioxide, but not in the leaves that had
no carbon dioxide. This suggests that this gas
must be needed for photosynthesis. The control
rules out the chance that high humidity or high
temperature in the plastic bag stops normal
photosynthesis.
4. Is oxygen produced during photosynthesis?
Result:
The glowing splint bursts into flames.
Interpretation:
The relighting of a glowing splint does not
prove that the gas collected in the test tube is
pure oxygen. However, it does show that it
contains extra oxygen and this must have
come from the plant. The oxygen is only given
off in the light.
Note that water contains dissolved oxygen,
carbon dioxide and nitrogen. These gases
could diffuse in or out of the bubbles as they
pass through the water and collect in the test
tube. So, the composition of the gas in the test
tube may not be the same as the composition
of the bubbles leaving the plant.
5. How will the gas exchange of a plant be affected
by being kept in the dark and in the light?
Interpretation:
Hydrogencarbonate indicator is a mixture of
sodium hydrogencarbonate solution with dyes
cresol red and thymol blue, acting as a pH
indicator in equilibrium with carbon dioxide. Its
color changes from orange/red to yellow with
increased carbon dioxide and to purple with
decreased carbon dioxide. In the experiment,
the indicator shows that in light (tube 1), plants
consume more carbon dioxide in
photosynthesis than they produce in
respiration. In darkness (tube 2), the plant
produces carbon dioxide. Tube 3, the control,
demonstrates that the presence of the plant
affects the solution. Although the indicator is
not specific for carbon dioxide, the likelihood of
other gases affecting the results is considered
less likely in the knowledge of leaf chemistry.
6. What is the effect of changing light intensity on
the rate of photosynthesis? (Method 1)
Result:
The rate of bubbling decreases as the lamp is
moved further away from the plant. When the
light is switched off, the bubbling stops.
Interpretation:
If the bubbles contain oxygen produced by
photosynthesis, then the rate of photosynthesis is
shown by the rate of oxygen bubble production.
So, the rate of photosynthesis increases as the
light intensity is increased. This is because the
plant uses the light energy to photosynthesise.
The oxygen is produced as a waste product. The
oxygen escapes from the plant through the cut
stem. We need to assume that the size of the
bubbles do not change during the experiment. A
fast stream of small bubbles could be the same
volume of gas as a slow stream of large bubbles.
7. What is the effect of changing light intensity on
the rate of photosynthesis? (Method 2)
Result:
The greater the light intensity, the quicker the leaf
discs float to the surface.
Interpretation:
As the leaf discs photosynthesise, they produce
oxygen. This is released into the air spaces in the
disc. The oxygen makes the discs more buoyant,
so as the oxygen builds up, they float to the
surface of the water. As light intensity increases,
the rate of photsynthesis increases.
8. What is the effect of changing carbon dioxide
concentration on the rate of photosynthesis?
Result:
The higher the concentration of sodium
hydrogencarbonate solution, the greater the
distance moved by the meniscus.
Interpretation:
As the concentration of available carbon dioxide
is increased, the distance travelled by the
meniscus also increases.
The movement of the meniscus is caused by
oxygen production by the pondweed, due to
photosynthesis. So, an increase in carbon dioxide
increases the rate of photosynthesis.
USE OF
PHOTOSYNTHETIC
PRODUCTS
→
6 CO2 + 6 H2O + energy (sunlight)
C6H12O6 (glucose) + 6 O2(Oxygen)
GLUCOSE
STARCH
SUCROSE
CELLULOSE
NECTAR
OXYGEN
RESPIRATION
STARCH
Sugar that is not needed for respiration is turned into starch and
stores or changes into other molecules.
Stored in stems, roots, tubers (ex. potato) seeds and fruits.
Starch molecules are added to the growing starch granules in the
chloroplast.
Glucose in cells = concentration increase = affects osmotic
balance ( not good )
Starch in cells = No change in concentration = all good
sucrose
When glucose is produced in photosynthesis it quickly changes
into sucrose for transport around the plant.
transported by the phloem - food-carrying vascular bundle
transport to parts of plants that DO NOT PHOTOSYNTHESIZE
(ex. growing buds, ripening fruits, roots, underground storage
organs, and basically nongreen parts )
Sucrose is used in many different ways. (transport of energy,
storage of energy etc. )
cellulose
Cellulose molecules are long chains of glucose.
Plant cell walls are made of cellulose, for structural
support.
Cellulose cell wall holds the contents of the cell but is
freely Permeable ( allows most molecules to pass through )
nectar
A mixture of sugars ( glucose, fructose, and sucrose )
Insect-pollinated plants need to produce and store nectar
Stored in floral tubes or spur, petals, sepals and base of the
ovary. (varies according to the plant's specific floral
morphology )
Produced by Nectaries ( glands that produce and secrete
nectar).
respiration
The process of (Cellular ) respiration oxidises glucose, formula of
photosynthesis is the opposite of respiration.
PHOTOSYNTHESIS
6 CO2 + 6 H2O + energy (sunlight)
→ C6H12O6 (glucose) + 6 O2
CELLULAR RESPIRATION
C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O + energy (as ATP)
Products of Respiration is then used for other chemical reactions
such as building-up of proteins.
respiration
respiration
MINERAL
requirements
MINERAL salts
MAGNESIUM ION
NITRATE ION
Used to make
CHLOROPHYLL
Used for the making of
AMINO ACIDS
ENZYMES and
CYTOPLASM of the cell
SOURCES
SOIL
Mineral ions are absorbed from soil. Salts can
come from rocks that have been broken down.
The minerals will be released after the plant dies
and decay, these minerals will pass on to other
plants. This is called the ‘Nutrient Cycle’.
FERTILIZERS
THREE MAIN TYPES OF FERTILIZERS
ammonium nitrate
superphosphate
compound NPK
all three contains nitrogen, phosphorus(for root development,
flowering, and fruiting) and potassium(for enzyme activation,
photosynthesis, and the synthesis of proteins and carbohydrates.) with
different ratios for slightly different purpose.
FERTILIZERS
ARABLE FARMING
‘Arable’ means land that is cultivated to grow
crops.
The ground is ploughed ( prepared ) with no
dead plants that have decayed meaning no
reused minerals.
Plants will obtain their minerals from fertilizers,
animal manure and/or sewage sludge.
deficiency symptoms
DEFICIENT IN NITRATE IONS
Stunned growth
Weak stems
Lower leaves turns yellow and die
Upper leaves becomes pale green
DEFICIENT IN MAGNESIUM IONS
No chlorophyll
Leaves turn yellow from the bottom of stem
up which is referred to as ‘Chlorosis’
water culture
A full water culture is a solution containing the salts
providing all necessary elements , with carbon dioxide,
water and sunlight needed for photosynthesis, to make
all the substances it needs to stay healthy.
Widely used in areas of horticulture like glasshouses.
Water culture solution is pumped along tubes where the
plant’s roots are placed in flat polythene tubes
water culture
potassium nitrate
potassium
phosphate
magnesium sulfate
calcium nitrate
EFFECTS OF
EXTERNAL FACTORS
limiting factors
A limiting factor is
something present in
the enviroment in such
supply that it limits life
processes
LIGHT INTENSITY
TEMPERATURE
CO2
CONCENTRATION
limiting factors
LIGHT INTENSITY
Light reaction depends on light intensity, the more
intense it is the faster the reactions will be up to a
certain limit.
Too little or Too much will slow down the reaction
TEMPERATURE
Dark reaction (light-independent) is affected by
the increase or decrease of temperature. The higher
the temperature is, the faster it will be.
If the temperature exceeds 50 degrees Celsius , it
will denature enzymes.
CO2 CONCENTRATION
The higher the concentration of CO2, the more material
there is to synthesize.
Excessive CO2= depends on other factors.
OTHERS
Limiting factors applies to other processes as well, including
added fertilizers increases crop yields, mineral ions being
limited by the absorbing area of roots, rates of respiration,
aeration of soil etc.
LEAF
STRUCTURE
STRUCTURE
EXTERNAL
INTERNAL
EXTERNAL
The broad, flat shape gives a large surface area
for the absorption of sunlight and carbon
dioxide.
Most leaves are thin, so carbon dioxide only
needs to diffuse across short distances to reach
the inner cells.
INTERNAL
CUTICLE
Made of wax
Water-proof layer
Regulate water balance, reduce
water loss.
Produced by the epidermal cells.
EPIDERMIS
UPPER
Thin and transparent cells that
allow light to pass through
NO chloroplast
Act as barrier to diseases
organisms.
LOWER
Protective layer.
Site of gaseous exchange in and
out of the cell.
PALISADE MESOPHYLL
Main region for
photosynthesis.
Cells are columnar (quite
long, packed with
chloroplast to trap light
energy.
Receive carbon dioxide by
diffusion from air spaced in
the spongy mesophyll.
SPONGY MESOPHYLL
Cells are more spherical and
loosely packed .
Contain lesser chlorophyll
compared to palisade
mesophyll cells
Air spaces allow gaseous
exchange.
STOMA & GUARDCELL
Each stoma is surrounded by
a pair of guard cells.
Guard cells control the
opening and closing of the
stoma
Water vapour passes out
during transpiration
Carbon dioxide diffuses in
and oxygen out during
photosynthesis
VASCULAR BUNDLE
Xylem vessels bring water and
minerals to the leaf.
Phloem vessels transport sugars
and amino acids away
( translocation )
distributed throughout the leaf,
ensuring efficient transport of
water, nutrients, and sugars
DISTRIBUTION OF CHLOROPHYLL
More chloroplast in the upper cells than in lower cells, upper cells
get more sunlight. this will reach chloroplast without being to
absorbed by many cell walls.
Thank
You