PHLOEM Flashcards
Phloem function
Transports assimilates
From their sources to their sinks
What is the phloem made of
Stacked sieve tube elements
Companion cells
Plasmodesmata to allow substances out
(Made of living cells)
Phloem structure adaptations
Sieve plates with pores allows continuous transport of assimilates
Sieve pores has spaces for substances
Phloem strong cell walls to withstand hydrostatic pressure
Has little cytoplasm and no organelles to maximise space to transport substances
Companion cells
Each sieve tube has a companion cell
They load sucrose from source cells to phloem through plasmodesmata
Source (phloem)
Where sucrose is loaded into the phloem
Sink
Where sucrose is unloaded from the phloem
why is sucrose transported and not other sugars
Sucrose is relatively metabolically inactive
Epidermal tissue plants
It’s the outer layer of plants
E.g: coats the stem
Vascular bundle tissue
1- Xylem
2- cambium
3- phloem
4- bundle cap
What is the cambium made up of
Meristem tissue
Meristem cells structure and function
Thin cellulose walls
No chloroplast
Small vacuole
Can divide by mitosis and differentiate into other cells
Why is the xylem dead
Lignin (woody substance) deposited into cell walls When differentiated to reinforce and waterproof them
This kills the cells
Easter egg tissue in a circle indicate it’s a…
Stem
Stem structure
Vascular bundle
Cortex surrounding bundle
Epidermis outer layer
Plant organs example
- leaf
- root
- stem
- flower
Leaf function
Stomata carries out photosynthesis
Root function
Anchors plant in soil
Absorbs mineral ions from soil
Stores starch
What tissue looks like a star
Xylem
Xylem function
Transports water from roots to the leaves and part of plants where it’s needed
Xylem adaptations
Made of dead cells aligned end to end to form continuous hollow tube
Narrow so does not break easily
Lignified walls to allow water to move (waterproofed)
Lignin strengthens to allow plant flexibility
Why is the flow of water in the xylem not impeded
Cohesion sticks H2O molecules together due to H bonds
Creating a continuous flow of water
Adhesion sticks water molecules together due xylem walls to carry water up
Root structure
Xylem that looks like a star
phloem between the star sides
Endodermis (with casparian strip inside) surrounding vascular bundle
Cortex outside endodermis
Epidermis outer layer
Root hair cells branching off
Symplast pathway
Movement of water through the cytoplasms of cell-cell
Through plasmodesmata
