3.3 Mass transport in plants Flashcards
Are the vessel in the xylem alive or dead ?
The components are dead
What does the xylem transport ?
Water and mineral ions
The walls of the xylem are lined with a waterproof polymer called lignin. What is the purpose of lignin ?
Lignin reinforces the walls of the vessel elements to provide structural support
What is transpiration ?
The process where plants absorb water through the roots, which then moves up through the plant and is released into the atmosphere as water vapour through pores in the leaves
What is the transpiration stream ?
The movement of water up the stem via the xylem
Explain the cohesion tension theory
Water molecules form hydrogen bonds with each other, causing them to ‘stick’ together (cohesion). The surface tension of the water also creates this sticking effect. Therefore as water is lost through transpiration, more can be drawn up the stem from the roots
How can transpiration rate be investigated ?
Using a potometer
How would you use a potometer to investigate transpiration rate ?
- Mark starting position of bubble
- Record distance moved by air bubble in given time period
What does the phloem transport ?
It is responsible for transporting sugars
What are some features of the phloem ?
- Sieve tube elements
- Companion cells
What direction does the xylem travel ?
Only upwards
What direction does the phloem transport ?
Upwards and downwards
What is translocation ?
It is an energy requiring process which serves as a means of transporting assimilates such as sucrose in the phloem between sources which release sucrose such as leaves and sinks
