Measurement of Cytosolic-Free Ca2+ in Plant Tissue

A range of techniques have been used to measure the concentration of cytosolic-free Ca²⁺ ([Ca²⁺ ]_cyt ) in plant cells. Fluorescent Ca²⁺ -sensitive indicators have been used extensively to measure plant [Ca²⁺ ]_cyt and a number of techniques are available for loading these into plant cells. Here we describe a method for measuring [Ca²⁺ ]_cyt in the guard cells of the model plant species Commelina communis by ratio photometry and imaging techniques using the ratiometric fluorescent Ca²⁺ -sensitive indicator fura-2.