4:4 Transport In Plants Flashcards
Compare xylem and phloem
Xylem vs Phloem:
Type of cell: cells are dead vs cells are alive
Presence of secondary cell wall: present in tracheids vs absent in phloem vessels
Energy required for substances transport: not required vs required
Direction of substance transport:
Upwards vs source cell to sink cell
Presence of companion cells: absent vs present
Presence of sieve tube elements: absent vs present
Describe xylem
Contains two water-conducting cells: tracheids and vessel elements. They are dead. No cytoplasm.
Describe tracheids (in xylem)
Long slender cells with tapered ends
Ends have gaps in secondary cell wall
Lignin hardens the cell wall and makes it water resistant
Water moves both vertically and laterally
They also have pits
Which is outer/inner for xylem and phloem?
Phloem is outside
Xylem is inside
Describe vessel elements in xylem
They are shorter and wider cells.
They have ours and perforations (sieve like things)
Perforations lack both primary and secondary cell wall l.
Describe phloem
It consists of sieve-tube elements and companion cells. They are alive at maturity and lack secondary cell walls.
Describe sieve-tube elements in phloem
Long thin cells with perforated ends called sieve plates
They are responsible for transporting sugars and other nutrients from photosynthesis
Describe companion cells in phloem
It provides materials to maintain the cytoplasm and plasma membrane of the sieve-tube elements.
What is cambium? (Plants yah)
Is a type of meristem tissue. It is the cells between the xylem and phloem that give rise to more of both cells
What are the 3 routes water travels from the root hair to the xylem
(Osmosis)
- Symplastic route via plasmodesmata
- Transmembrane route via water channels
- Apoplastic route within porous cell walls
What is the casparian strip (movement of water to xylem)
It forms a waterproof barrier at the endodermis.
Role of root pressure in water transport?
Root hair and epidermal cells constantly absorb ions from soil. these solutes are actively pumped into xylem.
The influx of ions lowers water potential of xylem below water potential of surrounding cells. Water from cells enter xylem.
This sets up a pressure that drives water against gravity.
Role of capillary action in water transport?
It can transport water to a limited distance against gravity. It occurs through adhesion, cohesion and surface tension.
Role of transpiration pull in water transport?
Transpiration refers to the loss of water as water vapor through the aerial parts of the plant.
This creates a tension that is transmitted from leaves to roots which pulls water from the roots to the xylem to the leaves. 
Describe transpiration in plants
- Water vapor defuses out of leaf
- Water evaporates inside of leaf.
- Water is pulled out of xylem by resulting pressure
- Water is pulled up xylem.
- Water is pulled out of root cortex by osmosis.
- Water is pulled from soil to root by osmosis.
