Maule Staining for Lignin: A Technique to Characterize Lignin Distribution in Arabidopsis Thaliana Stem Sections

For Maule staining, transfer the stem sections to a microcentrifuge tube. Add 1 milliliter of the 0.5% potassium permanganate solution to the tube containing the sections. Pipette the 0.5% potassium permanganate solution up and down gently, preferably, without disturbing the sections.

After a 2-minute incubation and repeat pipetting, let the microcentrifuge tube stand until all the sections settle down. Using a 1-milliliter pipette, draw out 700 microliters of 0.5% potassium permanganate solution. Add 700 microliters of distilled water to rinse out the potassium permanganate. Repeat three to four times or until the water solution stays clear.

After discarding the water, quickly add 1 milliliter of 3% hydrochloric acid until the deep brown color is discharged from the sections. This may happen within 3 to 5 minutes or may require two washes of 5 minutes each. Pipette out all of the 3% hydrochloric acid solution and immediately add 1 milliliter of concentrated ammonium hydroxide solution before imaging under bright-field lighting.