Transport system - Plants Flashcards
Identify the organs in a plant
Plant organs are the leaves, stems and roots of a plant.
Describe the external features of a leaf in relation to their functions
External features
- Thin structure with a large flat surface area
- Waxy cuticle
- Upper epidermal cells
- Paliside mesophyl
- Spongey mesophyl
- Lower epidermis
- Guard cells
- Stomata (pores)
What does a waxy cuticle do?
- The waxy cuticle is a waterproof layer to prevent rain from entering the leaf
What does the upper epidermis do?
- The Upper epidermis are transparent to let light energy pass through them to the cell layers below
What does the Palisade mesophyll do?
- Palisade mesophyll contains loads of chloroplasts making it the place where most photosynthesis happens
What does Spongey mesophyll do?
- Spongey mesophyll allows rapid gas exchanges by diffusion
What does the lower epidermis do?
- The lower epidermis is a lower lining containing guard cells which form stomata
What do guard cells do?
- The guard cells control the size of the stomata (pores) and
What does stomata do?
-The stomata takes in carbon dioxide and releases oxygen
Explain the need for transport systems in plants
move water and minerals upwards from the roots to the leaves and to move sugars, mainly downwards from the leaves to the rest of the plant
What is osmosis?
The movement of water molecules from a high concentration to a lower concentration down a concentration gradient through a selectively permeable membrane
Describe how root hair cells are specialised to absorb water
Extended surface area and large vacuole to allow absorption of water by osmosis
State the function of xylem vessels
Xylem vessels transport water and minerals upwards from the roots to the aerial parts of the plant
Describe the structure of xylem vessels
Xylem vessels are hollow tubes lined with rings or spirals of strong waterproof lignin. The hollow tubes have been formed from the remaining walls of dead cells and create a system of pipes to allow transport of water and minerals upwards from the roots
Explain why xylem vessels are lignified
The walls of the xylem vessels are lignified to allow them to cope with the pressure changes that take place when water is being transported upwards by the transpiration pull without collapsing in on themselves.
Describe the movement of water and minerals from the soil to the air
Water and minerals are moved into the root hair cells from the soil by osmosis and diffusion and then they are transported upwards through the xylem vessels by the transpiration pull. The transpiration pull moves the water and minerals up to the leaves where they exit the xylem vessel to enter either; the palisade mesophyll cells for use as a raw material for photosynthesis, or the air spaces in the spongy mesophyll layer where the water becomes water vapour that evaporates out of the leaf through a stoma by transpiration
State the definition of transpiration
Transpiration is the movement of water through a plant and loss of water from the aerial parts (leaves) of a plant by evaporation
Identify the structures in a leaf through which most water is lost by evaporation
Most water is lost by evaporation through the stomata that are found between pairs of guard cells mainly in the lower epidermis of a leaf
State how plants can control their water loss
Plants can control their water loss via transpiration by opening and closing their stomata. A pair of guard cells control the size of the stomata between them. When the stomata are closed water loss through the stomata is prevented. Stomata are mainly closed at night and open during the day
Identify the four factor that affect the rate of transpiration
- Temperature
- Surface area of leaf
- Wind speed
- Humidity
State the effect of each factor on the rate of transpiration
- As temperature, surface area and wind speed increases the rate of transpiration increases
- As the humidity increases the rate of transpiration decreases. As the humidity decreases the rate or transpiration increases
State the function of phloem tissue
Phloem tissue transports sugars from the leaves (where they are made by photosynthesis) to other parts of the plant
Describe the structure of phloem tissue
Phloem tissue is living and made up of two different types of cells - sieve tubes with sieve plates and combustion cells. Sieve tubes have no nucleus and holy end walls to allow transport of cytoplasm containing dissolved sugars between neighbouring phloem cells. A companion cell has enlarged nucleus that controls both itself and its neighbouring sieve plate cell
