Are you saying that you want to know if water absorbtion by roots can be affected by pH? If so, there is at least one indirect way, no need for a microscope. LMK if that's your question.

What is LMK? And no I know they are strongly affected by pH levels, I want to know how much. I am building a totaly synthetic environment in order to totaly datalog a plants life via my pc 24hrs per day. I am searching for a correlation between maximum permeabilty based on pH levels, and nutrient availability at that pH. Call it a plant specific diet. Plants absorb more, or become more permeable based on a pH level, which means that osmosis occurs at a given rate based on the same scale.

I, too, would like to know the meaning of LMK.
I believe that GOTOGUY should avail himself of a good text on plant physiology.Try Plant Physiology by Taiz and Zeiger,1998, Sinauer Assoc. The library call No. is QK 711.2, T35.
This excellent work might well give you all the answers

LMK = Let me know ;D

Ok I understand better now, thanks for the explanation. You have a good advice from taxonomist, Plant Phys. from Taiz and Zeiger is a very good reference book. Another good one is from Ross and Salisbury, same title. It will respond to many questions you may have concerning root function and nutrient availability, pH, etc.
One experiment I know of and that works well is one on observation of sudation. I will not go into details (unless you want me to). It consists of saturating the soil of the plant with water (you let sit your plant in water) and putting a dome over it. The soil and the air usually are water saturated overnight. Due to air saturation there will no longer be any transpiration (evaporation of water from leaves that is one process that drives water and nutrients up the plant). What you will observe in the morning, are little droplets around the leaves. These droplets show that although transpiration has stopped, there is another force driving up water up the plant. It's called root pressure. It occurs mainly in the tropics and generally when air is saturated with water.

You can easily adapt this experiment to what you want to do with pH. You can then play around with different levels of pH and see at what pH the formation of drops is either slowed or stopped.

For nutrient availability, it depends a lot on your plant. Most plants like it around 6 (4.8-6.2 roughly). You can start doing a search on the net to see if for your plant there are any papers or articles.

Living things do not respond to stimuli?
are you kidding? Your basic premise is ridiculous.

My premise is not ridiculus, that was a typo, what I was trying to say is that it would be impossible to monitor physical changes in permeability under a microscope, because the root sample would be dead, hence, no response to pH changes/permeability.

It is possible to study excised roots. Look at this paper. Water uptake by plant roots: an integration of views. It is possible to keep plant cells alive and functioning and study them under a microscope - plant cell biologists do it all the time. But, you said you were looking for a method to study permeability that did not involve microscopy. Nananine gave you a good example and others have provided excellent references. As others have told you, it is generally believed that the force driving water across roots is most commonly provided by tension created by transpiration from the shoot and extending to the root, but other processes are involved too. Stomata are very rarely found in roots, but structures in root cell membranes of specialized cells act as channels and are under cellular chemical control rather than basic physics. That process is what Nananine's experiment is demonstrating.

You might just find someone else has already found the answers to your questions. Someone on another thread mentioned Google Scholar. If a regular search using "Google" hasn't yielded the results you're looking for, try entering ... root permeability pH ... and see what you get.

The link below is the best I've seen on root structure and anatomy.

Here is a link that might be useful: Structure of Roots