3.3.4 The Phloem Flashcards
What are the organic compounds in the phloem dissolved in?
The organic compounds are dissolved in water to form sap
What do mature phloem tissues have in comparison to xylem cells?
Mature phloem tissue contains living cells, unlike xylem tissue
What is the function of sieve tube elements?
Sieve tube elements line up end to end to form a continuous tube
What is the function of sieve plates with sieve pores?
Allows for the continuous movement of the organic compounds.
What is the function of the cellulose cell wall in sieve tube elements?
Strengthens the wall to withstand the hydrostatic pressure that moves the assimilates.
What is the function of no nucleus, vacuole or ribosomes in phloem sieve tube elements?
Maximises the space for the translocation of the assimilates.
What is the function of the thin cytoplasm in sieve tube elements?
Reduces friction to facilitate the movement of assimilates.
What is the function of companion cells?
Each sieve tube element has a companion cell associated with it as companion cells control the metabolism of their associated sieve tube member
They also play a role in loading and unloading of sugars into the phloem
What is the function of the nucleus and other organelles in companion cells?
Provides metabolic support to sieve tube elements and helps with the loading and unloading of the assimilates.
What is the function of the transport proteins in the plasma membrane of companion cells?
Move assimilates into and out the sieve tube elements.
What is the function of large numbers of mitochondria in companion cells?
To provide ATP for the active transport of assimilates into or out of the companion cells.
What is the function of the plasmodesmata?
The link to sieve tube elements which allows organic compounds to move from the companion cells into the sieve tube elements
