Mass Transport In Plants
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The xylem tissues transports what from roots up to leaves
Water and mineral ions
What is a mass transport system?
System which moves substances over large distances
Describe the structure of the xylem tissue
Long tube structures Made from dead cells No end walls between cells (allows water to easily pass through)
What features of water enables it to move against gravity?
Cohesive and water tension
What is transpiration?
The evaporation of water from a plants surface
How is suction created in a plant?
Transpiration on leaves (water evaporates) Creates tension Draws water up xylem tissues
What factors affect transpiration? Explain why
Light - increase as causes stomata to open Temperature - increases as water has more energy so evaporates more Humidity - decreases transpiration as lower conc gradient Wind- increases transpiration as maintains conc gradient
What does the phloem tissue transport? Give two examples
Solutes Sugars and sucrose
Phloem tissue is also arranged in tube. What cells make up the phloem?
Sieve tube elements - living cells which form tube for transporting solvents Companion cells - carry out living functions for sieve cells as they contain few organelles and no nucleus
What is translocation?
The movement of solutes around a plant
Is translocation active or passive?
Active
Where does translocation move solutes from?
Sources (where they’re made) Sinks (where they’re used)
How do enzymes maintain a concentration gradient from source to sink?
Break down and change solutes at sink Creates lower concentration
What does the mass flow hypothesis suggest?
How solutes are transported through phloem by translocation
Explain the mass flow hypothesis theory
At the source, active transport moves solutes from companion cells to sieve tubes Lowers water potential of sieve tubes so water enters by osmosis from the phloem/companion cells At the sink, solutes are removed from phloem which increases the water potential Water leaves sieves by osmosis and lowers pressure in sieves Pressure gradient created and pushes solutes from source to sink