Concentrations

... know all effects. Anyway, 5500 USD is less than 18000 USD, isn't it? Do you need that much? Such chemicals are IMO used in at most micromolar concentrations.

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... you would be using them ;) However, if your aim is only to grow plants, not to do anything else with them, you could try both purities at several concentrations on few plants and see the effect. The impurities may have similar effect, since they are similar chemicals.

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If the membrane is semipermeable and the solute cannot cross the membrane, the concentrations will not be the same. However, the osmotic pressure could be the same (if there was not only pure water, but some solution).

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Its okay now! got it...had to convert concentrations from uM to M. thanks anyways :D

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Yes, that sounds too low, at least for those wavelengths where methyl red absorbs strongly. Did you correct your concentrations for the dilution you made as you mixed your stock solution into liquid prior to making the spectrometer measurement?

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