Plant Stems Flashcards
Describe the structure of the xylem vessels.
- Formed from dead cells joined end to end
- Have hollow lumen and no end walls
- Walls are thickened with lignin to help support the plant
- Lignin is waterproof which prevents water entering xylem cells
- Lignin is not present where pits are located
What is the function of the xylem vessels?
To transport water and mineral ions and provide support for the plant. Water and mineral ions move in and out of the xylem vessels through pits in the walls.
Describe the structure of the sclerenchyma fibres.
- Made up of dead cells running vertically up the stem
- Hollow walls
- Have end walls
- Cells thickened with lignin and contain more cellulose than other plant cells
What is the function of the sclerenchyma fibres?
To provide support
Describe the structure of the phloem tissue.
- Contains sieve tube elements and companion cells
What is the function of the phloem tissue?
To transport organic solutes from where they’re made to where they are needed.
What are sieve tube elements?
They are living cells that have no nucleus, few organelles and a thin layer of cytoplasm. They have lots of holes in them to allow solutes to pass through them.
What are companion cells?
Companion cells still have a nucleus, mitochondria, ribosomes and RER. They carry out living functions for them selves and the sieve tubes that they are always attached to.
