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Plant Nutrition
Photosynthesis
Why do living organisms need foods?
• Foods provide energy for metabolic activity
– reproduction
– growth
– excretion … etc
• Foods provide raw materials
– repair damaged parts
– growth
Energy for plants:
 Solar Energy
Raw materials for plants:
 Carbon dioxide
(from air)
 Nitrate, Sulphate, Phosphate &
water
(from soil)
General equation for
photosynthesis
Chlorophyll
Carbon dioxide + Water
Sun
Glucose + Oxygen
• Chlorophyll is a pigment for light absorption
• Chlorophyll is located in chloroplasts
• Glucose stores chemical energy
• Oxygen is released as by-product
Site of Photosynthesis
• Chloroplasts
• Chloroplasts in cells
of leaf and stem
• Chloroplasts contains
chlorophyll (green)
A chloroplast in
plant cell
Dicot. Leaf T.S. (x 100)
Chloroplasts
Double
membranes
Chlorophyll
stored here
Internal structure of chloroplast
Typical plant cell
Chloroplast
Typical Leaf Structure (Dicot.)
• Waxy cuticle is water-proof
• Single-cell layer epidermis
protect leaf but has no
chlorophyll
• Mesophyll cells contain the
most no. of chloroplasts
• Xylem tissue transport water
• Phloem tissue transport
organic food
• Stoma opens for air and
water vapour
• Guard cells open and close
staomta
Process of photosynthesis
It is a process made up by series of
reactions but generally divided into to
TWO continuous sets of reactions
Light Reaction
Dark Reaction
Factors affecting rate of photosynthesis
Factors
Changes
Effect to rate
Light Intensity
Stronger
Faster
Carbon dioxide
concentration
Higher
Faster
Temperature
Higher
Faster
Photosynthetic rate under different light
intensity and CO2 conc.
Photosynthetic rate
More amount of
CO2 provides more
raw materials
0.05% CO2
Heating effect of
light denatures
enzymes
0.03% CO2
Light Intensity
Stronger light
provides more energy
Effect of CO2 to Photosynthesis
Conical flask
Sun
Solid Sodium
Hydroxide
Sun
3 days
Leaf enclosed in conical flask
Leaf on the left becomes wilted as
CO2 in the flask is absorbed by
NaOH
Effect of light to Photosynthesis
Dark Blue
Aluminum foil
Sun
Brown
Starch Test after 3
hours
Destarch the plant in dark room
for 24 hours and cover a leaf
with aluminum foil
Shaded part remains brown
and exposed part turns dark
blue
Effect of chlorophyll to
Photosynthesis
Sun
Starch test after 3
hours
A destarched variegated leaf
Green part turn blue . Non-green
parts remains brown
Mineral Requirements for plants
• Macro-nutrient
– Nitrate, Phosphate and Sulphate ions
– Building up protein molecules
• Micro-nutrient
– Magnesium, Cobalt, Boron…etc
– Making of other essential molecules e.g.
chlorophyll
– As co-factors in enzymatic reaction
The End
Back
Back
Light Reaction
O
O
O
Sun
H
H
Oxygen gas
O
H
H
H
H
Water Molecules
Chlorplasts
H
H
Hydrogen Atoms
* Chlorophyll absorbs light energy
Dark Reaction
Back
H
H
H
H
Hydrogen Atoms from
Light Reaction
C
Series of Enzymatic
reaction
O
O
Carbon Dioxide from Air
Glucose