Transport of Pholem and structure Flashcards
What is the Phloem
The vascular tissue in charge of transport and distribution of the organic nutrients
What are the differences between Phloem and Xylem
Xylem is a one way transport upwards of water and minerals
while Phloem is a upwards and downwards transport of organic molecules.
Xylems outer cells are non living while the phloem cells are living but need support.
Xylem has no end walls while phloem has sieve plates which are end walls.
What is the phloem structure
Phloem are composed of sieve tubes, which are
columns of specialized cells.
Individual sieve tube cells
What is translocation and what is the difference between translocation and transpiration
transpiration is the loss of water vapour from the leaves and stems of plants while translocation is the transport of organic solutes in the phloem tissue as it is a transport system to give solutes to parts of plants that require solutes
what is translocation
Translocation is a process carried out by the phloem which links parts of the plant that need a supply of sugars and other solutes (i.e. amino acids) to other parts of the plant that have a surplus
Comparing phloem to animal circulatory system
(ask west)
both have a fluid flowing inside of tubes which moves due to pressure gradients
generating these pressure gradients requires energy, so flow of blood and phloem
sap are both active processes
there are no valves or central pump in phloem
why sucrose a good option for transport in phloem
its not readily available so it will not be metabolized immediately making it a good transport carb
how is Phloem loaded - apoplast
H+ ions are actively transported out of the
companion cells using ATP.
The build-up of H+ then flows down the conc.
gradient through a co-transport protein
Energy is released, and used to carry sucrose into
the companion cell-sieve tube complex.
what happens once the sucrose reaches the companion cell in the symplast route
Once the sucrose reaches the companion cell it is converted to
oligosaccharides to maintain the sucrose concentration gradient.
Water pressure in Translocation
1) what sparks it
2) what does this cause
3)what does the withdrawn of sucrose at the phloem sink end do
Build-up of sucrose and other draws water into the companion cell
through osmosis
This causes a build-up of pressure in the phloem
loss of solute causes a reduction in osmotic pressure
then water that carried the solute to the sink is then moved into the xylem.
where is the sucrose produced from
leaf cell (the source)
what are sinks and sources and are they apart of translocation
why must the phloem be able to transport in either direction
areas where sugars and amino acids are loaded into the phloem are called sources
areas where sugars and amino acids are unloaded and used are called sinks.
Sometimes, sinks can turn into sources and vice versa. This means that phloem must be
able to transport biochemical in either direction
yes
Sources and Sinks
Sources
mature green leaves
green stems
storage tissues in germinating seeds
tap roots or tubers at the start of growth season
sinks
Roots that are growing or absoribng mineral ions
Developing fruits
developing seeds
developing leaves
developing tap roots or tubers
are sieve cells living and what do they do?
Sieve tube cells are closely associated with
companion cells that carry out cellular functions.
Sieve cells are living and maintain sucrose and
organic molecules concentrations within the phloem
What are sieve tubes closely associated with
Sieve tube cells are closely associated with
companion cells that carry out cellular functions.
