Andrew wrote:
Potassium is not integrated into the plant strucure to any great
extent. Potassium is predominantly involved in ion channels. It
regulates potential across the cell membrane, providing energy for
cellular processes, maintaining osmotic pressure, etc. Take away
potassium and the cell's biological processes shut down. FWIW plants
actually have quite a high potassium demand, second only to nitrogen.
Andrew

So it acts like a catalyst ?
Is it the same for Ca and Mg ?
And Fe ??

Philippe