3.1.3 Plant Transport – Transport Tissues Flashcards
(12 cards)
State 3 functions of xylem tissue.
1) Transports water up the plant.
2) Transports minerals/ions up the plant.
3) Supports the plant (keeps it upright).
Describe the structure of xylem.
- The cells are joined end to end with no cross walls to form a continuous column.
- The vessels are hollow so have no organelles or cytoplasm.
- The walls are lignified (contain lignin)
Why do xylem contain no cytoplasm/organelles?
Cytoplasm/organelles would obstruct water flow.
What is the function of lignin in the xylem walls?
- Strengthens the wall and prevents collapse of the xylem.
- Waterproofs the wall to prevent water loss.
What is the advantage of the lignin being arranged in spirals?
It allows flexibility so prevents the stem from breaking.
What are the names of the unlignified parts of the xylem’s wall?
Bordered pits.
Why is it important that the pits allow movement of water out of the xylem vessel?
- They allow water to move to other vessels and other tissues.
- They allow water to bypass a blockage in the vessel
What is the function of phloem?
To transport sucrose and amino acids up and down the plant.
What are the 2 cell types that make up phloem tissue?
Companion cells and sieve tube elements.
Describe the structure of a sieve tube element.
- The elements are elongated and join end to end to form a column.
- There are pores in the end walls known as sieve plates.
- The cells have no nucleus, few organelles and little cytoplasm.
Why do companion cells contain a high number of mitochondria?
They are very metabolically active so need to produce a lot of ATP (to actively load sucrose into the sieve tubes).
Name the structures that link the sieve tube elements to the companion cells.
Plasmodesmata.
