plant nutrition
| Chapter 6 |
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Making carbohydrates using light energy
Plant nutrition
Living things take in substances into their body
Some repair old parts
Some create new parts
Some release energy
Substance is called nutrition
Organic substances
Protein, carbohydrates, fats, DNA, etc.
Animals cannot make these
Plants make their own
From inorganic substances
Carbon dioxide, water, mineral ions
Taken from air and soil
Photosynthesis
Making from light
Chlorophyll
In chloroplasts
Inorganic substances make carbohydrates and oxygen
Carbon dioxide + water --sunlight and chlorophyll--> glucose + oxygen
No reaction will happen if you just shine light that is not the sun or resembles the sun
Leaves and other parts of plant turn green because of this
Traps energy from sun
Passes energy on
Substances react
Produces glucose
Contains energy originally from the sun
The photosynthesis equation
Photosynthesis depends on enzymes to help it happen
Carbon dioxide + water --sunlight and chlorophyll--> glucose + oxygen
6CO2 + 6H2O --> C6H12O6 + 6O2
How a plant uses carbohydrates
Releasing useful energy
Needed to build protein molecules
From glucose by respiration
Releases oxygen
Storing, to use later
Plants make excess amounts of glucose
Store it as starch
Starch is not soluble in water
Not involved in internal plant chemical reactions
Plant breaks down stored starch when needs glucose
Making sucrose, for transport
Plants only make glucose in presence of chlorophyll
Other parts use glucose as delivery
Starch changed into sucrose
Carried one part to another
Through phloem
When destination is reached, changes into glucose
Making cellulose, to build cell walls
Each new cell, needs a new cell wall
Cellulose molecules make cell walls
Making nectar, to attract pollinators
Plants reproduce sexually
Flowers have male and female organs
Rely on pollinators to move pollen grains from one flower to another to fertilise the flower
This is because plants are practically still
Nectar
Different sugars
Made by photosynthesis
Making amino acids, to make proteins
Uses some glucose to make amino acids
Used for protein and growth
Need source of nitrogen
Gets from the soil
Forms nitrate ions
Transported all over plant where needed
Does not get enough nitrate ions
Not synthesise proteins well
Growth will be stunted or slowed down
Making other substances e.g. chlorophyll
Glucose can make chlorophyll
Not a protein
Contains magnesium
Need this as much as nitrate ions
Without magnesium
Leaves will turn yellow
Won't photosynthesise well
Will not grow well
Element | Nitrogen | Magnesium |
Mineral salt | Nitrate ions | Magnesium ions |
Why needed | To make amino acids, the proteins | To produce chlorophyll |
Deficiency | Weak growth, yellow leaves | Yellowing of leaves, often essentially between the veins |
Leaves
Plant organ
Most of chloroplasts are here
The structure of a leaf
Has a broad, flat part
Jointed to rest of plant with leaf stalk
Leaf stalk
Connections of parallel tubes
Vascular bundles
Collections of xylem tubes and phloem vessels running side by side which form the veins in a leaf
Carry substances around leaf
Chlorophyll
Where photosynthesis happens
Spreads out on membranes
Making sure sunlight reaches where it needs to
Thin leaf surface
Larger amounts of sunlight falls into the leaf
More cells photosynthesise
Helps carbon dioxide diffuse quicker
Large surface area
Stretches out and receives more sun
Larger amounts of sunlight falls into the leaf
Increases rate of carbon dioxide diffusion
0.04% of air is Carbon dioxide
Tissues in a leaf
Several layers of cells
Cuticle
Waterproof layer
Waxy layer
More of it on upper layer
Helps cells from a lot of heat
Transparent and allows light to pass through
To help reach each piece of chloroplast in the leaf
Protects the leaves
Prevents loss of water from leaf surface
Upper epidermis
Transparent
Protect internal tissue from mechanical damage and bacterial and fungal invasion
Packed together tightly
Reduces water vapour from leaving the leaf
No chloroplasts
Palisade mesophyll
Right below the upper epidermis and cuticle
Stacked side by side
Contains chloroplasts
Columnar cells closely packed together
Tall, narrow and somewhat cylindrical
Absorb light more efficiently
Makes the upper layer darker
Called this because of the way they are arranged
Vertical so more cells can fit
Able to photosynthesize
Close to top of leaf
To get the sunlight as soon as it enters
Chloroplasts
Spongy mesophyll
Interchange gases that are needed for photosynthesis
Less likely to go through photosynthesis than those in palisade mesophyll
Irregular cells loosely packed together
Leave numbers large air spaces
Allow rapid diffusion of gases throughout the leave
Some chloroplasts for photosynthesis
They have air spaces like a sponge
Able to photosynthesize
Not as well as palisade
Diffusion of air here
Intercellular space (air space)
This is where gas exchange takes place
Air from outside gets into the leaf and into the air space then the air gets into the chloroplast and photosynthesis takes place
Lower epidermis
Thinner than upper epidermis
Similar to upper epidermis
Large number of stomata
Contains guard and stomata cells
Cuticle
Cuticle is thinner
Does not get as hot
Does not lose much vapour than top
More on the lower surface than the upper surface
Stoma (plural - stomata)
Opening which allows gases to pass through it to into or out of the leaf
Take in and out gases
It is like a door for air
No water, stomata closes
No gaseous exchange photosynthesis ceases
Thousands of them all over the layer of the leaf
Surrounded by guard cells
High water potential, closes
Cells became turgid
Closes at night, prevents loss of water
Guard cell
Open and close to allow air into and out of the leaf
The opening is called a stoma
Multiple is stomata
Control the sides of the stoma
Similar to the frame of a door and the hinges
If a plant has enough water, the guard cells will open
This will allow exchange of gas by creating the opening
Control size of stoma opening
Xylem
Water and mineral are transported from roots to all parts of leaf
Phloem
To transport organic substances away from the leaf
Food, sugar, sucrose, etc.
Chloroplasts
Where photosynthesis happened
Has different features
Starch grain
Insoluble granules of composed of glucose
Used for energy
Membrane around chloroplasts
Cytoplasm around it from a cell
Enables movement
Moves to regions of light
Stack of membranes containing chlorophyll
Allow concentration gradients to store energy
Thylakoids
Helps absorb sunlight
Features in the picture (not needed in f4)
Intermembrane space
Between inner and outer membrane
Stroma lamellae
Connect different thylakoid pieces
Increases photosynthesis efficiency
Keep a distance so they do not clutter
Thylakoid
Absorb sunlight
Contain chlorophyll (obviously)
Stroma
Provide volume
For protection
Inner membrane
Regulates passage of material in and out the chloroplast
Outer membrane
Protein import
Exchange of ions
Etc.
Granum
Where light reaction takes place for photosynthesis
Lumen
Space inside thylakoid discs
Molecular oxygen is produced from water during photosynthetic light-dependent reactions
Conversion of light energy into chemical energy
Collects energy from sun and breaks it down
Factors affecting photosynthesis
Supply of raw material
Carbon dioxide and water
Quantity of sunlight
Energy for reactions
Temperature
Affecting enzyme activity
Quantity of chlorophyll
How fast photosynthesis happens
Controls
Series of experiments where you control what a leaf gets and see what happens when it is deprived of something
You test the starch in leaf after experiment to see if there was any changes in a covered area
Limiting factors
A factor that is in short supply, which stops an activity happening at a faster rate
Light intensity
Plant in the dark or in dim light
Increasing light, increased rate of photosynthesis
If it increases at a specific point it won't photosynthesise any further
Light is no longer the limiting factor
Carbon dioxide
More carbon dioxide, increased rate of photosynthesis
Temperature
Warm environment, great rate of photosynthesis
Only great at an optimum temperature
Not a cold day, not a hot day
Too cold, won't photosynthesise
inactive
Too hot can't photosynthesise anymore
Denaturing
Stomata
Diffuses carbon dioxide into leaf
When closed, photosynthesis can't occur
Closes during hot weather
