| Why do plants need transport systems | Plants need substances like water, minerals, and sugar to live. They also need to get rid of waste substances. They also have a small surface area to volume ratio with a relatively high metabolic rate. Exchanging substances by direct diffusion would be too slow. |
| What is the xylem tissue responsible for | Is transport water and mineral ions in solution. These substances move up the plant from the roots to the leaves. |
| What is the phloem tissue responsible for | It transports sugars (mainly sucrose) up and down the plant. |
| What is the vascular system | The xylem and phloem together |
| Where is the xylem and phloem located in the roots and why is it there | It is located in the centre surrounded by the phloem to provide support for the root as it pushes through the soil |
| Where is the xylem and phloem located in the stems and why is it there | They are located near the outside, with phloem being on the outer edge, to provide a sort of scaffolding that reduces bending |
| Where is the xylem and phloem located in the leaves and why is it there | They make up a network of veins, with phloem being on the underside, which support the thin leaves |
| How are xylem vessels adapted for their function | - they are very long, tube like structures formed from cells joined end to end
- there are no end walls on these cells, making an uninterrupted tube that allows water to pass through the middle easily
- the cells are dead, so they contain no cytoplasm
- their walls are thickened by lignin, which helps with support and stops them from collapsing inwards
- water and ions move in and out of the vessels through pits in the walls |
| How is phloem tissue adapted for its function | - contains phloem fibres, phloem parenchyma, sieve tube elements and companion cells
- sieve tube elements have no nucleus, and only has a very thin layer of cytoplasm and few organelles
- companion cells provide energy for active transport of solutes |
| How do you dissect plant stems | - use scalpel to cut a cross section of the stem as thinly as possible
- use tweezers to gently place them in water, this stops them from drying out
- transfer to dish containing stain ( TBO- stains the lignin in the walls of xylem blue-green) and leave for a minute
- rinse off the sections in water and mount each one onto a slide |
