Transport In Plants Flashcards
How many transport systems does a plant have
They have 2 systems, the xylem and phloem
What does the xylem tissue do
Transports water and minerals ions from the roots to the leaves, stem and flowers
What does the phloem tissue do
The phloem tissue transports dissolved sugars and other soluble food molecules from the leaves to all of the other areas of the plant
The sugars are made during photosynthesis which is why they come from the leaves
What are meristems
The place where plant stem cells are produced
What is the process of moving sugars around the plant through the phloem called
Translocation
What is the structure of the xylem
- the xylem vessels are made form dead xylem cells
- they form tubes which run through the plant stems
- there are no cell walls at the end of these cells
- strengthened with a substance called lignin
What is the structure of the phloem
- Phloem vessels are made of living cells
- the walls of the cells do not completely break down
- sieve plates are formed (they are small holes in the end wall which allow the dissolved sugars to pass through)
- the connection of phloem stems forms a tube which allows dissolved sugars to be transported
How do the vascular bundles provide support in the leaf
- ## in the leaf they form a network that supports the softer leaf tissue
How does the evaporation of water from the leaves work
The water molecules are taken up from the roots to the leaves by the xylem cells.
- as the water molecules travel up into the leaves, the guard cells become turgid, and the stomata open
- the water flows out of the leaf through the stomata, due to the concentration gradient
- inside the leaf, there is a high concentration of water, but outside in the air, there is a low concentration
- while the stomata are open, CO2 is then able to flow into the leaf, which is used to fuel photosynthesis
Transpiration stream definition
The chain of water molecules that travel up the Xylem cells
Transpiration meaning
The evaporation of water from the leaves
What factors effect the rate of transpiration
- humidity
- light intensity
- temperature
- air flow
How does light intensity effect rate of transpiration
- Brighter light means that more photosynthesis will occur, meaning that more carbon is needed.
- This mesns the stomata will be opened more to allow carbon to enter
- More water will be lost from leaf when stomata are open meaning higher rate of transpiration
How does temperature affect the of transpiration
The warmer it is, the higher the rate of transpiration
- the water particles will have ore energy, so they will be more likely to evaporate and diffuse out of the stomata
- low temperature means evaporation takes place slower
How does wind speed effect transpiration
The rate of transpiration increases and decreases depending on if the wind speed is increased or decreased
- if the airflow is high, water particles in the the outside of the leaf will be blown away quicker. This means that there will be rapid changes in the concentration gradient, and it will remain high
How does humidity effect rate of transpiration
Humidity is the measure the rate of how much water is in the air at a given time
If there is a lot of water in the air, the concentration gradient will be low, meaning that transpiration will happen slowly,
If there is low humidity, there will be a high concentration gradient, which means that transpiration will go happen quicker
Photosynthesis occurs in the guard cells but not the epidermal cells.
Explain why this is important in the control of the rate of transpiration in the plant.
4 marks
-> photosynthesis makes sugars in guard cells
-> epidermal cells dont photosynthesise so lower in sugar than guard cell
->epidermal cells higher water potential than guard cells
-> water enters guard cells by osmosis
-> increasing turgidity of guard cell opens stomata
-> opening / size of stoma affects transpiration rate
Why is the inner cell wall of the guard cells thicker than the outer cell wall of the guard cells
Prevents the guard cells from expanding evenly, forcing the guard cells to develop a curved shale, helping the stoma open
How do guard cells control opening of stomata
-> light levels trigger ions (such as K+ ions) to be transpferredd into the guards cells
-> increases concentration of the guard cells and lowers water potential of it
-> water moves into the guards cells via osmosis (area of high water potential to low water potential)
-> guard cells swell and become turgid
Why do the guard cells have rings of cellulose
-> to stop the cell from expanding widthways and only letting it expand lengthways when water moves into it
-> means the stoma can open
A student uses a simple potometer to study the effect of different temperatures on the cut shoot of a plant.
What does the potometer actually measure?
Volume of water taken up by shoot
Sieve plates are found in plants
What is their location and function
Found in phloem and allow movement of sucrose
Fanconi anaemia is a genetic disorder. It results in the bone marrow being destroyed.
This causes a decrease in the numbers of red blood cells, white blood cells and platelets.
Explain two possible symptoms of Fanconi anaemia.
-> tiredness due to lack of red blood cells
-> project to infection due to lack of white blood cells
-> slow blood clotting due to lack of platelets
Describe what happens during transpiration
-> water evaporates on the surface of sponges mesophyll
-> water diffuses through stomata pores
Describe how Potometer scan be used to investigate the effect of light on transpiration rates
Can measure gas bubble movement over a specific amount of time, and see how that movement changes over varying distances
Why is a heat sink used in Potometer
-> to absorb heat generated from lamp in order to stop it from changing the results
-> heat may mean that the distances closer to the lamp have much higher transpiration rates then they should have due to increased KE of the particles
Photosynthesis occurs in the guard cells but not the epidermal cells.
Explain why this is important in the control of the rate of transpiration in the plant.
-> photosynthesis makes sugars
-> guard cells have higher sugar concentrations than epidermal cells, because epidermal cells done photosynthesise but guard cells do
-> guard cells there by have lower water potential than epidermal cells
-> when high amounts of photosynthesis takes place water moves into guard cells due to differences in WP
-> guard cells become turgid, amd due to the difference in thickness of cell walls, the stomata opens
-> higher rate of transpiration
When the outside of a plant, around the phloem is ringed, the part above is swollen
Explain why
-> phloem in that section is removed due to the plant being ringed
-> swelling caused by build up of sugar that can’t be transported
-> (sugar produced in leaves)
How do vascular bundles provide support in the stem
How do the vascular bundles provide support in the roots
in the root they are found in its centre, enabling the to act as an anchor - the root can bend as the plant moves in the wind
