Plant Stems Flashcards
What are the 3 types of plant vessel?
- Phloem
- Xylem
- Schlyrenchma fibres
What is the function of the xylem?
- Transports mineral ions and water up the plant
- Structural support
What do xylem vessels look like?
Very long tube like structures formed from dead cells joined end to end
How are xylem vessels found together?
Bundles
What are the proportions of xylem vessels like?
Cells are longer than they are wide
What is the lumen of xylem vessels like?
Hollow with no cytoplasm
What are the walls of the xylem vessels like?
No end walls
What allows the water and mineral ions to pass up xylem vessels?
It is an uninterrupted tube
How do xylem vessels support the plant?
They are thickened with a woody substance – lignin
How do water and mineral ions move in and out of xylem vessels?
Through pits in the walls where there is no lignin
What is the function of the sclerencyhma fibres?
- Structural support
- NOT transport
How are the sclerencyhma fibres similar to the xylem vessels? 3
- Longer than they are wide
- Hollow lumen
- Thickened with lignin
How are sclerencyhma fibres different to xylem vessels?
- More cellulose
- Have end walls
- Don’t contain pits
What is the function of the phloem tissue?
Transport soluble organic solutes e.g glucose from where they are made to where they are needed – translocation
How is the phloem tissue similar to the xylem tissue?
Formed from cells arranged in tubes
How is the phloem different to the xylem tissue?
Used only as a transport tissue, not support
What 2 types of cell does phloem contain?
- Sieve tubes elements
- Companion cells
What are sieve tube elements?
- Living cells joined end to end to create sieve tubes
- Their end walls have many holes in them to allow water through
What are sieve tube element cells like?
- Very thin layer of cytoplasm
- Few organelles
- No nucleus
How are the cytoplasm of sieve tube element cells connected?
Through holes in the sieve plates
Why can’t sieve tube elements survive on their own?
Lacks nucleus and other organelles needed for cell function
What is the function of the companion cells?
To carry out living processes for both itself and the sieve tube element cells
Give an example of a function of the companion cell
To provide energy for the active transport of solutes
Where are xylem vessels and phloem tissue found in the stem?
Grouped together to form vascular bundles
Where is the sclerencyhma tissue found in the stem?
On the outside of vascular bundles
What is the function of starch?
- Stores excess glucose in a plant
- When the plant needs more glucose it breaks down starch
What is cellulose made up of?
Long unbranched chains of beta glucose joined by 1-4 glycosidic bonds
How is cellulose different to starch?
Glycosidic bonds are straight so the cellulose chains are straight
How are cellulose chains linked together?
Large numbers of hydrogen bonds form strong threads called microfibrils
What do the strong threads in cellulose mean?
Cellulose can provide structural support for cells
What feature of the cell wall gives plant fibres strength?
Made up of cellulose microfibrils in a net like arrangement
What is the function of cellulose?
Forms cell walls in plants
What else other than cellulose makes plant fibres strong?
Secondary thickening of cell walls
What happens in the secondary thickening of cell walls?
- When structural plant cells e.g xylem and schlerenchyma have finished growing
- They provide a secondary cell wall between the normal cell wall and the cell membrane
- Secondary cell wall is thickened with more of a woody substance called lignin
