Measurement of cytosolic-free Ca²⁺ in plant tissue

A range of techniques have been used to measure the concentration of cytosolic-free Ca(2+) ([Ca(2+)](cyt)) in plant cells. Fluorescent Ca(2+)-sensitive indicators have been used extensively to measure plant [Ca(2+)](cyt) and a number of techniques are available for loading these into plant cells. Here we describe a method for measuring [Ca(2+)](cyt) in the guard cells of the model plant species Commelina communis by ratio photometry and imaging techniques using the ratiometric fluorescent Ca(2+)-sensitive indicator fura-2.