9.1 Xylem and Phloem Flashcards
What type of tissue is the xylem made from?
Non-living
What are the 2 main functions of the xylem?
Transport of water and ions + support
In what direction does material flow in the xylem?
Up from roots -> leaves and shoots
What is the main structure of the xylem?
Xylem vessels
What are xylem vessels in terms of their structure?
Long, hollow structures made by columns of cells fused together end to end
What are the other 2 tissues associated with the xylem?
- Thick-walled parenchyma
2. Xylem fibres
Where can thick walled parenchyma be found?
Packed around xylem vessels
What is the function of thick walled parenchyma?
Store food + contain tannin deposits
What is tannin?
Bitter chemical - protects plants from herbivore attack
What are xylem fibres?
Long cells w/ lignified secondary walls
What is the function of xylem fibres?
Contain lignified secondary walls - provide extra mechanical strength
Do xylem fibres transport water? Yes or no
No
How can lignin be laid down in the walls of xylem vessels?
Lignin can form rings, spirals or solid tubes, w/ lots of small unlignified areas called bordered pits
What are bordered pits? What is their function?
Small, unlignified areas in the lignified walls of the xylem fibres.
Bordered pits = where water leaves the xylem
What type of tissue is the phloem made from?
Living
What is the function of the phloem?
Transports food in form of organic solutes around plant from leaves, where they’re made via photosynthesis
What does the phloem supply cells with?
Sugars + amino acids, needed for respiration + synthesis of molecules
What is the direction of the flow of materials in the phloem?
Up and down the plant
What are the main transporting vessels in the phloem?
Sieve tube elements
What is the structure of sieve tube elements?
Many cells joined end to end, forming a long, hollow structure
What’s the difference between xylem vessels and phloem tubes?
Xylem vessels = lignified
Phloem tubes = unlignified
What are sieve plates?
Areas between sieve tube elements where walls become perforated, resulting in many gaps + a sieve-like appearance, allowing phloem contents to flow through
What are companion cells?
Active cells next found next to sieve tube elements that supply phloem vessels with all their metabolic needs
What are sieve tube elements and companion cells linked by?
Plasmodesmata - microscopic channels through cellulose cell walls linking cytoplasm w/ adjacent cells
