The best way to conserve root samples for FCR (ferric chelate reductase activity) analysis is to freeze them at -80°C. This will ensure that the samples are preserved in the best possible condition until you receive the chemical product bathophénanthroline disulfonic Acid 98% needed for the analysis. Freezing at -30°C may not be enough to ensure that the samples are preserved in the best possible condition.

I agree with Peter Donkor :)

Thank you for your answer @Peter Donker and @Andrew Paul McKenzie Pegman