help! translocation

We were going through it today and I have just revised my notes, but I still don't understand the different components and how they work together to create movement of the sucrose :frown:

please can someone help explain or give me some details where I can get further help.
Thank you.

Reply 1

Revenged

eh?... you're not making sense...

translocation is genetics...

i.e. Robertsonian translocation is a cause of Down's syndrome...

Reply 2

mrs_matt_tuck

translocation is the movement of organic solutes (such as sucrose) through a plant. It happens in the phloem. The main things that are transported are amino acids and sugars.
1. Sugars - are transported from the leaves, where they are made by photosynthesis, to actively growing regions or storage sites.
2. amino acids are made in the root tips and are carried to growing areas to make proteins.

It is the movement of dissolved organic substances to wjere they are needed in the plant. It is not known how this occurs exactly, just that it is an active process needing ATP energy from respiration.

Translocation moves substances from sources to sinks. The source is where the substance is made, meaning a higher concentration of the substance at this point. The sink is the area where it is used up, so there will be a low concentration of the substance here. An example would be: the source for sugars is in the leaves and the parts where this is needed are the food storage organs and the growing points in roots, stems and leaves. These would be the sinks. As there are dfferent concentrations at the sources and sinks, a concentration gradient is formed. Meaning substances can flow from a high concentration to a low concentration.

The mass flow hypothesis is the closest we have to explaining phloem transport (ie translocation).
1. Dissolved sugars from photosynthesis (sucrose) are actively transported (using ATP energy from respiration) into sieve tubes of the phloemin the leaves. This is the source. The water potential is therefore lowered as the solute potential increases. So water enters by osmosis (from a high water potential to a low). This then causes a high pressure to devolp in the sieve tubes at the end of the phloem.

2. At the sink the sugars will leave the phloem to be used up, so increases the water potential as solutes have left. This is again by osmosis. The pressure inside the sieve tubes is therefore lowered here.

3. This pressure gradient then exists between the source (high pressure) and the sink (low pressure). Pushing the sugars from the source to the sink along the sieve tubes to where they are needed.

Although there are arguments for and against this method, it is generally accepted as what occurs during translocation.