Translocation Flashcards
(20 cards)
What is Translocation?
Translocation is the process of moving sugars (mainly sucrose) and other nutrients through the phloem of a plant from where they are made (the source) to where they are needed or stored (the sink).
Where does translocation happen?
In the phloem, which is made of long tubes called sieve tube elements.
What supports the sieve tube elements in the phloem?
Companion cells support the sieve tube elements.
What is the first step in the translocation process?
Loading the Phloem at the Source.
What does the source usually produce during photosynthesis?
Sucrose.
How do companion cells transport sucrose into sieve tube elements?
By active transport (needs ATP).
What happens to the concentration of solutes in the phloem when sucrose is loaded?
It increases.
What process causes water to move into the phloem from the xylem?
Osmosis.
What is the result of water moving into the phloem?
It creates high pressure in the phloem at the source.
What pushes the phloem sap through the sieve tubes?
The pressure at the source.
What is the flow of phloem sap from high pressure to low pressure called?
Mass flow or pressure flow.
What is the third step in the translocation process?
Unloading at the Sink.
What happens to sucrose at the sink?
Sucrose is taken out of the phloem.
How can sucrose be removed from the phloem at the sink?
By active transport or diffusion.
What happens to the solute concentration when sugar is removed at the sink?
It lowers.
What happens to water at the sink after sucrose is removed?
Water leaves the phloem and returns to the xylem.
What effect does removing sugar have on pressure at the sink end of the phloem?
It lowers the pressure.
What type of energy does translocation require?
Energy (ATP).
Is translocation unidirectional or bidirectional?
Bidirectional.
What hypothesis explains the translocation process?
The pressure-flow hypothesis.
