Cytosolic Ca2+ Determinations in Studying Plant Responses to Salinity and Oxidative Stress

Salinity and oxidative stress can transiently elevate cytosolic free Ca²⁺ ([Ca²⁺ ]_cyt ) of plant cells. The [Ca²⁺ ]_cyt increase may be part of a signaling cascade or cell death, depending on cell type, the magnitude and the duration of stress exposure. Several approaches for determining [Ca²⁺ ]_cyt responses are available to plant biologists, but some require highly specialized equipment. Here we describe protocols for using aequorin as a standard [Ca²⁺ ]_cyt reporter, with output detected with a plate-reader luminometer.