Transport systems- Plants

Xylem

• Transports water and mineral ions from the roots to the other parts of the plants by transpiration

• Dead cells that form hollow tubes

Phloem

• Transports sucrose and amino acids from the leaves to other parts of the plant by translocation

• Living cells that contain sieve plates with holes to allow the substances to pass through.

Adaptations of the root hair cell

• Contain mitochondria which release energy for active transport

• Increase the surface area of plant roots, increasing the rate of active transport and osmosis

How does the root hair cell take in water and mineral ions

• Mineral ions enter the cell by active transport

• Water concentration of the cell cytoplasm is reduced due to the presence of mineral ions

• Water moves into the root hair cell by osmosis

The route of water through the plant

1. Water from the soil enters the plant through osmosis

2. Water from the root hair cell moves into the root cortex cells by osmosis

3. Water from the root cortex cell moves into the xylem cells by osmosis and moves up the xylem towards the leaves via transpiration

4. Moves into the mesophyll cells by osmosis

Transpiration

Loss of water from a plant by evaporation and diffusion through the spongy mesophyll cells and stomata

Functions of transpiration

• Transporting mineral ions

• Provides water to keep cells turgid and support the structure of the plant

• Provides water for photosynthesis

• Keeping the leaves cool as heat energy is removed when water evaporates

How does air movement affect transpiration rate

• As wind speed increases, transpiration rate increases

• Water molecules are quickly blown away from the leaf; this creates a concentration gradient and more water vapour diffuses from the leaf.

How does temperature affect transpiration

• Temperature increase → Transpiration rate increases

• Water vapour molecules have more kinetic energy and move around faster

How does humidity affect transpiration

• Humidity → Decreases transpiration rate

• Humid air has higher concentration of water vapour, reducing the diffusion gradient between the inside of the leaf and outside air.

How does light intensity affect transpiration

• Light intensity increase → Transpiration rate increases

• Stomata opens more and increases rate of photosynthesis

Method- factors affecting transpiration

• Cut shoot underwater to prevent air from entering the xylem

• Make sure the apparatus is airtight and seal with Vaseline to make sure it’s airtight.

• Dry leaves of the shoot

• Remove the capillary tube to allow a single air bubble to form and place the tube into the water

• Set up a lamp 10cm from the leaf

• Record the starting location of the bubble, leave for 30 minutes and record the end location of the bubble.

• Change the light intensity and repeat the experiment

Rate of transpiration formula

Distance moved by air bubble/ time

Results- factors affecting transpiration

Light intensity increase → rate of transpiration increases because more stomata will open and more water is being lost by evaporation and diffusion