Translocation Flashcards
What is translocation?
The transport of assimilates in a plant
What are assimilates?
Substances that are made by the plant using substances that have been absorbed, such as sugars and amino acids
What is the source?
A part of a plant that loads assimilates into the phloem sieve tubes
What is the sink?
A part of a plant that removes assimilates into the phloem sieve tubes
What is active loading?
Energy is used to H+ out of the companion cell, decreasing their concentration in the companion cell, creating a concentration gradient. The H+ comes back into the companion cell if they are bonded to sucrose
What is the mechanism that allows active loading to happen called?
Cotransport or secondary transport
How is sucrose moved in the source?
Sucrose enters the sieve tube element, so the water potential is lower so water enters by osmosis from the surroundings, increasing the sieve tubes hydrostatic pressure.
What is sucrose used for in the source?
Photosynthesis, storage, energy
What happens to sucrose in early spring?
It is in the roots and goes to the rest of the plant to encourage growth
What happens to sucrose made in spring and summer?
It is loaded into the sieve tubes or it goes to other areas that may be growing or use it in storage
How is sucrose moved in the sink?
It can be diffused out by active transport out of the sap, which causes that water potential to increase so water moves out of the cell to reduce the hydrostatic pressure at the sink
How does sucrose travel in the phloem?
Water enters the sieve tubes at the source increasing the hydrostatic pressure and at the sink water leaves the sieve tubes decreasing the hydrostatic pressure. This pressure gradient is set up in the sieve tube so the sap goes from an area of high to low pressure.
