Plant Nutrition
Chapter 6
NUTRITION
• Taking in useful substances
To
make
new
parts
To repair
old parts
Nutrition
To
release
energy
Type of Nutrition: Organic substances
To
make
new
parts
To
repair
old parts
Nutrition
To
release
energy
Type of Nutrition: Inorganic substances
Photosynthesis
●
Definition: process by which plants
manufacture carbohydrates from raw
materials using energy from light
●
The sunlight energy has to be trapped
then used in the reaction
Chlorophyll and Chloroplast….?
Photosynthesis
●
Chloropyhll
○
○
○
The green pigment that makes plants
look green
Inside chloroplast
Absorbs sunlight energy and convert it
into chemical energy for formation of
carbohydrates
Photosynthesis
● Word and Balanced Equation
○ Sunlight: provides the energy to
drives the reactions
○ Carbon dioxide is the molecule used
to make sugar (in combination with
the water
You must be able to recall
both of these equations!
Photosynthesis
Leaves
● Leaves come in all shapes and sizes but
what features do they have in common
to maximize photosynthesis?
• Attached to the stem by a stalk or petiole
that contain vascular bundles
• The leaf stalk continues into the leaf as
midrib
• From the midrib branches a network of
veins which deliver water and salts and
carry away the food made in the leaves.
• The leaf blade or lamina is broad to receive
sunlight
Match each design feature of a leaf with its
purpose
Leaf Transverse Section
Leaf Transverse Section
Leaf Transverse Section
Cuticle
• A layer atop the epidermis
• Waxy layer secreted by epidermal cell
(waterproof layer)
• Function?
Epidermis
• Covers the upper and bottom surfaces of
leaf
• Does not contain chloroplast, except guard
cells
• Consists of transparent cells
• Function?
Pores or stomata
• Holes that allows water and gases to diffuse
in and out of the leaves
• Each stoma is surrounded by a pair of guard
cells that can change their shape to change
the size of pore
Opening and Closing of Stomata
Palisade Mesophyll
•Located at middle layer of leaf, nearer to the top
of leaf
•Contain a lot of chloroplasts
•Arranged like a fence, palisade cells are closely
packed together
Spongy Mesophyll
•Located beneath palisade mesophyll
•Not as closely packed as the cells in the
palisade mesophyll layer with large air
space between them
•There are not as many chloroplasts in as
there are in the palisade mesophyll cells
Vascular Bundle
• Vascular bundle with xylem and phloem.
Provides transport and support.
• Xylem vessels carry water
• Phloem tubes carry away substances (such
as sucrose) made by the leaf
Leaf adaptation
To obtain carbon dioxide, water and
sunlight
Leaf adaptation - to obtain carbon dioxide
Carbon dioxide
- obtained from air
- because carbon dioxide only about
0.04% of the air, leaf must very
efficient at absorbing it
How?
Leaf adaptation - to obtain carbon dioxide
For an efficient gaseous exchange:
● Large surface area of the leaf.
● Leaves are very thin.
● Air spaces in spongy mesophyll
Leaf adaptation - to obtain carbon dioxide
Leaf adaptation - to obtain water
The branching network of
veins provides a good water
supply to the
photosynthesizing cells
Leaf adaptation - to obtain sunlight
1. Sunlight penetrates => thin and transparent epidermal cells =>
2. To expose chlorophyll to sunlight => many chloroplasts in the
palisade cells and arranged broadside on =>
3. To expose as much of the leaf to sun (and air)
a. Broad and flat surface
b. Position and arrangement
c. Large surface area
Leaf adaptation - to obtain carbon dioxide, water and sunlight
Uses of Glucose
Respiration to provide energy to drive
the metabolic reactions needed to
keep the plant alive
Conversion to other molecules such as
oils and proteins. This may require
mineral salts (e.g. nitrates)
Conversion to sucrose to transport to
other parts of the plants via phloem
(translocated)
Glucose
NOTE: glucose is not a good storage
molecule because it is reactive and
soluble water.
Conversion to cellulose for the
construction of plant cells walls.
Conversion to starch for storage. Starch
is insoluble so does not affect water
potential of plant cells.
Nitrate and Magnesium ions
B
A
Structure of Chloroplast
Practical Activity
Test for Starch
Test for Chlorophyll
Test for Sunlight
Test for Carbon dioxide
Test for Oxygen Produced
Limiting factors in Photosynthesis
A limiting factor is a factor that controls a process. Light
intensity, temperature, CO2 concentration and availability
of H2O are all factors which can control the rate of
photosynthesis.
B
A
C
Greenhouse
Allows conditions to be
controlled.
Maximize the rate of
photosynthesis
Faster photosynthesis = growth
increase (Yield increase)
The importance of photosynthesis