average rate of nutrient uptake
 

I am interested in how much of the different nurients is taken up by hydroponically grown plants.
for example how much phosphorus does a tomato plant take up during frutingstages?
Does anyone know were to find such information?

This is actually a topic of my own interest.
There are some quite interesting studies around, - I recently posted a link to a Brazilian study about the hydroponic growth and nutrient requirements of potatoes here. Just a few days ago I came across a study that showed amazing data about Nitrogen uptake of lettuce during all stages of growth.

Some papers are free and there are scientific pay sites as well. In many cases the studies target or focus on very particular studies, though. In the best case they give you valuable information and almost what you were indeed looking for - and in the worst, they just focus on stuff you are not interested in or confuse you even more. Some are easier to read and understandable others hardly or not intelligible at all for non-academics in the field and/or those who are not fluent in scientific language. The other question is if you can actually and practically use the data you've finally found. As a matter of facts, there is no site around (I know of) that gives you a set of the informations you are looking for. You need to work hard and have dedication ;)

Google is even a better friend if you use the right keywords! :)
Example:Google Books

thanks
 

Is the data on lettuce available for free, can you post a tread.
I found som data on tomatoes but the unit they used i did not recognise it was me/l. Do yo know what it is

You mean 'mM/l'? That would be millimolar per liter (one one-thousandth of a mole per liter) That is exactly what I was talking about when I said that there is often use of scientific language (or units in this case) that aren't commonly known by laymen. But then again, for a chemist millimolar are like foot for a carpenter. ;)

Here is the link (PDF) RESPONSE OF HYDROPONIC LETTUCE CULTIVARS
TO DIFFERENT TREATMENTS OF NITROGEN:

Refine your google keywords (by using more scientific terms) and you'll find plenty of that stuff.