if the protocol say use 95% ethanol to dissolve 2,4-D powder. Can I use absolute ethanol to dissolve the powder? Then I will adjust volume by water. Does anybody give me the concept of PGRs preparation? Why we should to dissolve by specific solution and adjust by another solution?
Regards,
Thanida
Hello Thanida,
using either 100% or 95% alcohol should work fine. (whereas 70% alcohol may not). Use of a solvent is necessary as most growth regulators will not dissolve easily (or not at all) in pure water. An old-time rule of thumb is disolve auxins in alcohol and cytokinins in dilute alcali (e;g; 1 N KOH or NaOH). Adjusting the volume with water allows reducing (in proportion) the amount of solvent introduced in the medium along with the regulator (with possible undesirable effects). Depending on the experiment, you may want to use a control where the same quantity of solvent +water (without regulator) is added to the medium to check for possible toxicity or media pH modification. I would advise you do this systematically if you ever have to use DMSO as a solvent as it can be very toxic to plant cells...
Hope this helps
Best regards
Absolute ethanol is not longer absolute after you open the bottle since the alcohol starts to hydrate rather quickly (it depends on RH) due to its hygroscopic nature. A 4-5% water makes the 2,4-D more soluble; besides commercial (96% ethanol) is cheaper than absolute ethanol!
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