Mass transport in plants Flashcards
What is the function of the leaves
Photosynthesis
Producing glucose
What substances does the phloem transport
Organic substances (E.g. Sucrose, glucose )
What are the properties of the sieve tube elements
Living cells
No nucleus
Few organelles
What are the properties of companion cells
Provides ATP for the active transport of organic substances
What is the ‘ Source ‘ cell
Leaf cell/ Chloroplast
What is the ‘ Sink ‘ cell
Respiring cell/ Root cell
Why does the ‘ Source ‘ cell gain water ?
Organic substances produced
Lowers water potential
Water enters via osmosis
Due to water potential gradient
Why does the ‘ Sink ‘ cell lose water ?
Uses up organic substances
Higher water potential
Water leaves via osmosis
Due to water potential gradient
What does the increase and loss of water create
Hydrostatic pressure increase and decrease at the Source and sink cell
Inducing a pressure gradient
What is the first step in translocation
Chloroplast/Source cell produces organic substance
Establishes concentration gradient of sucrose
How and why does sucrose transport into companion cell
Concentration gradient of sucrose established
Diffuse in via facilitated diffusion (Protein Channel)
How is a concentration gradient of H+ ions established
H+ ions transported from companion cell
Into cell wall using energy
Creates H+ gradient
Moves down gradient
Into sieve tube elements
How does the co-transport of H+ ions occur
Via protein co-transporters
For sucrose -> Sieve tube element
Why is water potential lowered at the sieve tube
Due to the increase in concentration of sucrose
Why does water enter the sieve tube and what is its effect
Water potential is lowered
Due to organic substances
Moves in via osmosis
High hydrostatic pressure in the sieve
Forces solution down to sink
