Comparative Detection of Calcium Fluctuations in Single Female Sexual Cells of Tobacco to Distinguish Calcium Signals Triggered by in Vitro Fertilization Water Channels Are Involved in Stomatal Oscillations Encoded by Parameter-Specific Cytosolic Calcium Oscillations Arabidopsis transcriptional response to extracellular Ca2+ depletion involves a transient rise in cytosolic Ca2+ Effect of Extracellular Calmodulin on the Cytosolic Ca2+ Concentration in Lily Pollen Grains