Plant Transport Structure Revision Carousel Flashcards
What two components of phloem tissue are concerned with transport?
-Sieve tube elements
-Companion Cells
Plant transport systems consist of 2 major specialised vascular tissues. Name these, state their transport material and the direction of transport.
-Xylem;water, soluble mineral ions upwards
-Phloem;assimilates upwards and downwards
What is the purpose of lignin in xylem vessels?
Strengthens vessel wall and prevents collapse
What is the purpose of parenchyma in xylem tissue?
To separate and support the vessels and act as a packing tissue
What tissue is found between the xylem and phloem? What is its function?
Meristematic tissue which is a source of stem cells
What allows water to move continuously via the apoplast pathway?
Cohesion, by diffusion
What allows water to move through cells via the symplast pathway and by which mechanism of movement
-Different water potential of cytoplasm of adjacent cells
-Water moves by osmosis
Explain the significance of Casparian strip.
Waterproof hence locks the apoplast pathway between the cortex and the medulla, forcing water and dissolved mineral ions to pass through the selectively permeable membrane into the cytoplasm, filtering out of toxic chemicals
Why does the presence of starch in the endodermis suggest that an active process is involved?
Starch acts as a store of sugars, which can be released and respired to release energy for active processes
Describe three adaptations of xylem vessels that relate structure to function.
1)Dead cells aligned end to end to form a continuous column
2)Tubes are narrow so the water column doesn’t break easily and capillary action can be effective
3)Bordered pits allow sideways movement of water between vessels
4)Lignin allows stretching of xylem (spiral, annular or reticulate patterns) as plant grows
How are companion cells adapted for active loading?
Many mitochondria to produce ATP
What is the Casparian strip?
A band of waterproof, waxy suberin around each endodermis cell (on cell wall)
Why do sieve tube elements contain no nucleus and very little cytoplasm?
Allows space for mass flow of sap to occur
Describe 2 major pathways taken by water to move between cells.
-Apoplast-through spaces in cell walls and between cells (mass flow not osmosis)
-Symplast-moves through cytoplasm and between cells via plasmodesmata
How do bordered pits form and what is their purpose?
Where lignification is incomplete, leaving gaps in the cell walls, the bordered pits in 2 adjacent vessels are aligned to allow water to leave one vessel and pass into the next, as well as leave xylem
