Osciillating pH fluxes inside and outside of a growing root hair

This movie is of the tip of a growing root hair of the plant Arabidopsis thaliana (mouse ear cress). A pH-sensitive fluorescent dye has been added to the medium it is growing in and the plant itself has been engineered to produce a fluorescent protein in the cytoplasm. Both the dye and the protein become brighter as the pH rises (becomes less acidic) and dimmer as the the pH drops (more acidic). The pH oscillates as the root hair grows, with the interior of the cell becomeing acidic as the outsuide pH rises and vice versa. This pattern relfects protons moving in and out of the cell across the cell membrane as the root hair grows.

For more research into this response see:
Monshausen et al (2007) PNAS 104:20996-21001

Cardenas (2009) Plant Signal Behav. 4:4-8