Plant Structures and Functions Flashcards
What is the equation for photosynthesis?
6CO2 + 6H2O + light energy → C6H12O6 + 6O2
What is photosynthesis?
A process that plants and algae use to produce their own food
What are the limiting factors of photosynthesis?
- Low temperature
- Dim light
- Low CO2 concentration
What are xylem and phloem?
Specialised plant cells
How is phloem specialised?
- They contain sieve tube elements which have very little cytoplasm so there is lots of space to transport sucrose
- They have companion cells which have lots of mitochondria which supply energy from respiration for active transport for sucrose in and out of sieve tubes
How is xylem specialised?
- They have no cytoplasm or cell contents which means there is more space for water containing mineral ions to move through
- They have holes in their walls called pits that allow water and mineral ions to move out
- Their walls are strengthened with lignin rings which makes them very strong and prevents them from collapsing
- They have no end walls so they form a long tube that water can easily flow through
What is transpiration?
Movement of water from the roots of a plant to the leaves
What is the process of transpiration?
- Water enters the roots through osmosis
- Water is drawn up the stem through the xylem from the roots
- Water is drawn out of the xylem and to the leaves
- Water vapour evaporates from the leaves mainly through the stomata
Where are stomata normally located?
On the lower surface of the leaf
What happens when guard cells of the stomata take in water by osmosis?
They swell up and the stoma opens
What happens when guard cells of the stomata lose water by osmosis?
They become flaccid and the stoma closes
What is translocation?
Transportation of sucrose around a plant
What do xylem and phloem help with?
Transport of things around the plant
How is sucrose transported in translocation?
In phloem
Where is sucrose stored?
In storage organs (as starch)
What adaptations do leaves have to assist with photosynthesis and gas exchange?
- Air covers most of the surface of each cell so gas exchange can take place
- Epidermis cells and waxy cuticle are transparent to allow light to pass through to the photosynthetic cells
- Leaf is flat to give larger surface area
- Xylem cells bring water for photosynthesis
- Phloem cells remove sugars produced in photosynthesis
- Stomata allow carbon dioxide from air into the leaf and allow oxygen to leave the leaf
- Internal air spaces increase surface area for diffusion of gases
What do chloroplasts do?
Convert light energy from the sun into sugars
What factors effect transpiration?
- Light intensity - increases the rate of transpiration because high light intensity causes the stomata to open which means more water evaporates from the leaf so more water is taken up to replace this
- Air movement - wind blows moist air away from the stomata keeping the concentration gradient high, the more air movement there is the higher the rate of transpiration
- Temperature - the higher the temperature the more energy the water molecules have so they move faster so the higher the rate of transpiration
What is a potometer?
A piece of equipment used to measure the rate of transpiration
How do you measure the rate of transpiration using a potometer?
Distance moved by the air bubble / time taken
What adaptations do plants have for living in dry conditions?
- Waxy cuticle to reduce water loss
- Stomata sunk in pits to reduce water loss
- Leaves have hairs to trap moist air around stomata
- Rolled leaves to reduce air movement around stomata
What adaptations do plants have for living in tropical conditions?
- Large leaves to take in as much light as possible
- Stems and leaves that climb up the trees to obtain more light
- Leaves with ‘drip tips’ so that water runs off them
What adaptations to plants have for living in water logged soil?
- Spongy tissue in their roots that stores oxygen
- Fine surface roots that take oxygen in at the water surface
What is a tropism?
A plant’s response to a stimulus (a change in the environment) by growing
