Symbiosis Rhizobium - leguminosa - Science topic

I'm trying to buy a Vibratome VT-1000S. What are other brands and model similar to this one. Purpose is to section Medicago truncatula nodules.

Also it's effects on plants.

I know rhizobia bacteria fix nitrogen when symbiotic with leguminous plant.But when culture on nitrogen free media that's time can fix atmospheric nitrogen.

I have inoculated Rhizobial isolates to newly cultivated soybean plants in a controlled condition. They formed nodules but there is a huge variation among plants dry weight. More important thing is that control plants got more weight than inoculated nodulating plants  in agar and Fahraeus N-free medium in glass house. 

Can anyone in the US recommend low-phosphate and low-nitrogen fertilizers to use for Medicago truncatula arbusculation and nodulation assays, respectively?

In drylands, rhizobial community are in low density. In your opinion, in a experiment to measure the rhizobial population in sites where you expect to be low density, what is the most appropriate serial x-fold dilution to determine the most probably number (MPN)? 10-fold, 5-fold, 2-fold?

If someone can help me in getting a Rhizobial strain that infect chickpeas (Cicer arietinum) to produce N2 fixing nodules and it should have GFP/GUS/DsRED or anything like that as a visualization tag.

I wish to know if there are any plant species that have NCR peptides but have determinate nodule growth as the NCR peptides are found in IRLC genomes.

We are growing leguminous cover crops hydroponically for nitrogen release studies but we are experiencing serious root fungal infection (Pithium fungi typical symptoms) on the root system in our dry run setup. If has anyone encountered this problem in similar work before, please assist me with the solution.