Topic 6 - Plant Structures and Their Functions Flashcards
Plants are able to make their own food by ______________
Plants are able to make their own food by photosynthesis
What organisms photosynthesise?
Green plants and algae
What is the glucose produced from photosynthesis used for?
To make larger, complex molecules that the plants or algae need to grow which make up the organisms biomass
Define biomass
The mass of living material
What happens to the animals biomass?
It travels its way through the food chain
Where does photosynthesis take place?
Chloroplasts
State the equation for photosynthesis
Carbon Dioxide + Water -> Glucose + Oxygen
6C02 + 6H20 -> C6H1206 + 602
What type of reaction is photosynthesis?
Endothermic
What factors affect the rate of photosynthesis?
Light Intensity
Concentration of CO2
Temperature
When investigating the effect of light intensity on the rate of photosynthesis, what type of plant do you use?
A canadian pond weed
When investigating the effect of light intensity on the rate of photosynthesis, what corresponds to the rate of photosynthesis?
The rate of oxygen production
When investigating the effect of light intensity on the rate of photosynthesis, what type of light is used?
White light
When investigating the effect of light intensity on the rate of photosynthesis, where does the oxygen produced go?
Up to the gas syringe
When investigating the effect of light intensity on the rate of photosynthesis, what is the independent variable?
The distance of the light from the pondweed
When investigating the effect of light intensity on the rate of photosynthesis, what is the dependent variable?
The rate of oxygen production
When investigating the effect of light intensity on the rate of photosynthesis, what are examples of control variables?
Temperature
Carbon dioxide concentration
Explain how photosynthesis contributes to a plant’s biomass?
Photosynthesis produces glucose which is used to make larger, complex molecules that make up the mass of the plant’s living material (the plants biomass)
State three limiting factors of photosynthesis
Temperature
Carbon Dioxide concentration
Light Intensity
Why is light needed for photosynthesis?
Because it transfers the energy needed
Describe the relationship between light intensity and photosynthesis
As the light level is raised, the rate of photosynthesis increases up to a point where there is another limiting factor
How do you calculate the light intensity?
Light intensity ∝ 1 / Distance²
What does the inverse square law tell you?
Where if you halve the distance, the light intensity will be four times greater
Describe the relationship between carbon dioxide concentration and photosynthesis
As the amount of carbon dioxide is raised, the rate of photosynthesis increases up to a point where there is another limiting factor
Describe the relationship between temperature and photosynthesis
As the temperature is raised, the rate of photosynthesis increases up to a point where the enzyme begins to denature and the reaction will slow down and eventually stop if the temperature continues to increase
Why are high temperatures needed for photosynthesis?
Because the enzymes involved need around 45*c to be working at its optimum
Root hairs take in _______ and ____
Root hairs take in minerals and water
What is useful about the surface of plants root?
It is covered in millions of hairs which increase the surface area for absorbing water and mineral ions from the soil
True or False? The mineral ions are usually higher in the root hair cells than in the soil?
True
What process takes in mineral ions into the root hair cell?
Active Transport
What tube transports food?
Phloem
What are phloem tubes made of?
Elongated living cells with small pores in the end walls to allow stuff to flow through
What do phloem tubes mainly transport?
Food substances (mainly sucrose) made in the leaves to the rest of the plant
What happens to the food substances after it has been moved?
Used immediately or for storage
What process is involved with the phloem tubes?
Translocation
Do phloem tubes require energy?
Yes
In what directions do phloem tubes go?
Both
What tubes transport water?
Xylem
What are xylem tubes made of?
Dead cells joined end to end with no end walls between them and a hole down the middle
What are xylem tubes strengthened with?
A material called lignin
What do xylem tubes carry?
Water
Mineral Ions
Where do xylem tubes carry stuff to?
To the stem and leaves
What process is involved with the xylem tubes?
Transpiration
What is transpiration?
The loss of water from a plant?
Transpiration is the loss of _____ from the plant
Transpiration is the loss of water from the plant
What causes transpiration?
Evapouration and diffusion
Where does most transpiration happen?
At the leaves
What does the loss of water cause?
A shortage of water which causes a increase in water being drawn up from the bottom of the plant
What is also carried along the transpiration stream?
Mineral ions
Explain how water moves through a plant in the transpiration stream
Water is lost from a plant’s leaves by diffusion and evapouration. This creates a slight shortage of water in the leaves, so more water is drawn up through the xylem vessels to replace it. This in turn means there’s more water drawn up from the roots, so there’s a constant transpiration stream through the plant
What are stomata?
Tiny pores on the surface of a plant
Where are stomata mostly found?
On the lower surface of leaves
What do stomat allow to diffuse in or out of a leaf?
Carbon Dioxide
Oxygen
Water Vapour
What are stomata surrounded by?
Guard cells
What do guard cells do?
Change shape to control the size of the pore (stomata)
What happens to the stomata when the guard cells are turgid?
The stomata is open
What happens to the stomata when guard cells are flaccid?
The stomata is closed
State the factors that affect transpiration rate
Light Intensity
Temperature
Air Flow
How does light intensity affect environmental factors?
Stomata begin to close as it gets darker as photosynthesis can’t happen in the dark
How does temperature affect transpiration rate?
The warmer it is, the faster the transpiration happens as the particles have more energy to evaporate and diffuse out of the stomata
How does air flow affect transpiration rate?
The better the air flow, the faster the area is cleared of water particles meaning the area has an area of lower concentration which means the greater the transpiration rate
How do you estimate the transpiration rate?
By using a potometer to estimate transpiration rate
What equipment is used to measure transpiration rate?
A potometer
What does a potometer do?
Measures the water uptake by a plant
What is the equation for transpiration rate?
Distance moved / Time taken
A potometer was used to estimate the transpiration rate of a plant cutting
The bubble moved 25mm in 10 minutes
Estimate the transpiration rate
= Distance moved / Time taken
= 25 / 10
= 2.5 mm min^-1
Explain how low light intensity affects the rate of water uptake by a plant?
In low light conditions the stomata will close, as photosynthesis requires light which means it would be a waste to keep the stomata open if there is no light
This means that very little water can escape, so the rate of water uptake by the plant decreases
What are leaves adapted for?
Photosynthesis and gas exchange
What is good about a leaf being broad?
There will be a larger sa exposed to light
What is good about a leaf having alot of chloroplasts in the palisade layer?
This means that they’re near the top of the leaf where they can get the most light
What is good about the upper epidermis of the leaf being transparent?
So the light can pass through it to the palisade layer
What is good about a leaf having xylem and phloem tubes?
They provide the leaf with water for photosynthesis and take away the glucose produced
They also help support the structure
What is good about a leaf having a waxy cuticle?
It helps reduce water loss by evaporation
How are the tissues of leaves adapated for gas exchange?
The lower epidermis has lots of stomata
The spongy mesophyll tissue contains air spaces which increases the rate of diffusion
Give an example of a plant adapted to live in extreme environment
A cacti
Why do extreme plants have small leaves and spines instead of leaves?
To reduce the surface area for water loss
And to stop animals eating the plant
Why do extreme plants have curled leaves?
To reduce air flow close to the leaf trapping water vapour near the surface and reducing diffusion
Why do extreme plants have thick waxy cuticle?
To reduce water loss by evapouration
Why do extreme plants have a thick fleshy stem?
To store water
Why do extreme plants have fewer stomata?
To reduce water loss
Why do extreme plants have stomata sunken in pits?
Makes them lower than the surface which reduces the air flow close to the stomata
Give three reasons why cacti have spines instead of leaves?
To reduce surface area - to reduce water loss
Prevent eating of the plant by animals
To reduce air flow - to reduce water loss from evapouration
What are auxins?
Plant hormones which control growth at the tips of shoots and roots
Auxin move through the plant in ________
Auxin move through the plant in solution
Where do auxins promote growth?
In the shoot
Where do auxins inhibit growth?
In the root
What is phototropism?
The plants response to light
What is gravitropism?
The plants reponse to gravity
What do auxins change?
The direction of root and shoot growth
Shoots are __________ phototropic
Shoots are positively phototropic
What happens when a shoot is exposed to light?
It grows towards it
As when exposed to light it accumulates more auxin on the side that’s in the shade than the side thats in the light which makes the cells grow faster on the shaded side so the shoot bends towards the light
Whats the point of the shoot growing towards the light?
So it can absorb more light for photosynthesis
Shoots are __________ phototropic
Shoots are negatively phototropic
What happens when a shoot is exposed to gravity?
It grows away from gravity
As more auxins on the lower side
Roots are __________ gravitropic
Roots are positively gravitropica
What happens when a root is exposed to gravity?
It grows towards gravity
As the auxins collect on the lower which causes the top to grow faster
Roots are __________ phototropic
Roots are negatively phototropic
What happens when a root is exposed to light?
It grows away from it
As the root begins to accumulate auxins on the shaded side which inhibits cell elongation on the shaded side
Which direction do roots always grow?
Downwards
Which direction do shoots always grow?
Upwards
Name a part of a plant that is positively gravitropic
The roots
Plant hormones have many _________ uses
Plant hormones have many commercial uses
Give examples of plant hormones being used
Weedkillers Growing from cuttings Controlling fruit formation Producing seedless fruit Controlling the ripening of fruits Controlling seed germination
What hormone is used for weedkillers?
Auxins from broad-leaved plants
How do weedkillers work?
Broad-leaved auxins totally distrup the growth patterns for broad-leaved plants only
What hormone is used for the growing from cuttings?
Rooting powder (auxins)
How do growing from cuttings work?
The auxins cause root production which start growing as new plants
What hormone is used for the control of flower and fruit formation?
Gibberellins
How does controlling flower and fruit formation work
By letting the plant germinate faster than usual and under conditions in which they wouldn’t usually flower
What hormone is used in producing seedless fruit?
Gibberellins
How does producing seedless fruit work?
The gibberellins grow the fruit but not the seeds
What hormone is used in controlling the ripening of fruits?
Ethene
What is the advantage of controlling the ripening of fruits?
Allows the fruit to be picked while it’s still unripe
What hormone is used in controlling seed germination?
Gibberellins
How does controlling seed germination work?
By reducing the required conditions the seeds need when germinating
Why could it be good to control seed germination?
You can grow seeds at all times of the year and make sure all the seeds in a batch germinate at the same time
State one way in which gibberellins can be used commercially?
Used to control flower/fruit formation
Used to produce seedless fruits
Used to control seed germination
In what part of a cell does photosynthesis take place?
Chloroplasts
Apart from water vapour, what gas is needed for photosynthesis?
Carbon Dioxide
Name the two products of photosynthesis?
Oxygen and Glucose
Why is photosynthesis described as an endothermic reaction?
Because it takes in the suns energy for the reaction
What effect would a low carbon dioxide concentration have on the rate of photosynthesis?
The rate of photosynthesis would be lower
What effect would a temperature above 45*c usually have on the rate of photosynthesis?
Decrease the rate of reaction as that is the point at which the enzymes denature
How are root hair cells adapted to their function?
By having a large surface area to increase the rate of absorption
By what process do phloem tubes transport sucrose around a plant?
Translocation
Describe the structure of xylem vessels?
Dead cells joined end to end with no end walls
Strengthened by lignin
What are stomata?
Tiny pores on the surface of the plants
What is the role of stomata in transpiration?
The way water is lost
Give three factors that affect the rate of transpiration
Air Flow
Temperature
Light Intensity
Describe how you’d use a potometer to estimate the rate of transpiration
Calculate the distance moved and divide by the time
Give three way in which a typical leaf is adapted to absorb the maximum amount of light for photosynthesis
Broad - Large surface area for light
Transparent top layer - Ensure light can reach the chloroplasts
Chloroplasts packed at top palisade layer - Maximise the efficiency as the top has the highest light level
Give two ways in which a leaf is adapted for efficient gas exchange
Air gaps in leaf to increase rate of diffusion
The lower epidermis has lots of stomata
How do curled leaves help a plant living in dry conditions
Reduces air flow which reduces the transpiration rate
What are auxins
Growth hormones found in plants
What does positively phototropic mean?
Grows towards light
Roots are positively gravitropic
Explain the role of auxins in this response
Auxins accumulate at bottom of root
Grow faster at bottom, causes root to grow downwards
Explain how selective weedkillers work
Auxins mess with growth patterns of broad-leaved plants
List three things that gibberellins stimulate in plants
Seed germination
Root and shoot elongation
Flowering, and fruit patterning
Describe a commercial use of the plant hormone ethene
Can use to ripen the fruit as soon as it arrives to the store meaning it can be picked unripe
Describe a commercial use of the plant hormone ethene
Can use to ripen the fruit as soon as it arrives to the store meaning it can be picked unripe
Give the layers of the leaf
Upper epidermis
Palisade mesophyll
Spongy mesophyll
Lower epidermis
How do you remember the pallisade mesophyll layer?
Pallisade = fence
Fences are closely packed together
How do you remember the spongy mesophyll?
Sponge has holes in it, air gaps
