transport in plants Flashcards
What does the xylem transport throughout a plant?
The xylem transports water and mineral ions
What direction does the xylem flow?
Only up
What does the phloem transport?
The phloem transports assimilates such as sucrose
What direction does the phloem transport materials?
Both up and down
What is the cambium?
It is a layer of meristem cells found in between the xylem and phloem in the stem
Where is the xylem found in the stem?
The xylem is closest to the center of the stem
What are meristem cells?
Meristem cells are cells that divide to produce new cells
Where is the phloem found in the stem?
The phloem is farthest from the center with the cambium separating the xylem and phloem
What is the epidermis?
The epidermis is the outermost layer of the plant almost like skin
What is the xylem made of?
Dead cells so water and mineral ions can be transported
What is the phloem made of?
Sieve tube elements and companion cells
What is sclerenchyma?
It offers support and structure around cells as its thickened with lignin and cellulose
What is collenchyma?
Found near epidermis.
thick cellulose walls provides flexibility and aids growth.
What is parenchyma?
its a soft packing-tissue that fills spaces between other tissues.
What can parenchyma store?
stores starch in roots
chloroplasts to photosynthesise
has air spaces in aquatic plants to aid with buoyancy
What are the main functions of the xylem?
provide structural support. transport water and mineral ions
What is the structure of the xylem?
Long hollow tubes made up of thick, lignified dead cells
What is the role of lignin in the xylem?
lignin is deposited in the xylem cell walls, killing the cells, but makes it waterproof and stronger
what are bordered pits in the xylem?
they are small non-lignified regions of the xylem. they allow water and mineral ions to move laterally between xylem vessels
What does the parenchyma store?
The parenchyma stores food and contains Tannin
What is Tannin?
A bitter-tasting chemical that protects plant tissues from attacks by chemicals and infection from bacteria and fungi
What is transpiration?
The loss of water from the stomata in the leaves due to evaporation
What are the adaptations of sieve tube elements?
Elongated
No nucleus
Very little cytoplasm
Does the xylem contain dead/alive cells?
The xylem is made up of dead cells
Does the Phloem contain dead/alive cells?
The phloem is made up of living cells
What are the roles of water?
Photosynthesis
Structure and support
Transport
Cooling
What are the adaptations of root hair cells?
Microscopic size allows it to easily penetrate soil particles.
Large SA:V ratio
Thin surface layer so short diffusion
High conc. of solutes maintain steep water potential gradient.
What are the 3 ways water moves from the root hair to the xylem?
Apoplast - through intercellular space
Symplast - through plasmodesmata
Vacuolar - same as symplast but can pass through vacuoles as well
What is the slowest pathway water can take to reach the xylem?
The vacuolar pathway is the slowest
What is the slowest pathway water can take to reach the xylem?
The vacuolar pathway is the slowest
What is the casparian strip?
A band of waxy material called Suberin that waterproofs the vascular bundle
What happens at the casparian strip?
Water in apoplast pathway can’t continue, it it forced into the cytoplasm of the cell, joining the symplast pathway. This ensures any harmful solutes in the water are excluded as carrier protein won’t admit them into the cell.
What is root pressure?
Root pressure is a tiny force that gives water a ‘push’ up the xylem. However it can’t account for water reaching the top of tall trees.
Root pressure ≠ transpiration
What is the evidence for root pressure?
Root pressure increases with temp suggesting it is dependent on active transport.
Cyanide (affects mitochondria) reduces root pressure. Suggesting it’s an active process.
Guttation
If oxygen levels or respiratory substances fall, so does root pressure.
