Visualizing Cytoplasmic Calcium in Polarizing Zygotes and Growing Rhizoids of Fucus Serratus

¹ Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, Devon PL1 2PB, U. K.

Evidence for spatial variations in cytoplasmic free Ca²⁺ in tip-growing cells is briefly summarized. Methods are described for detecting such gradients using fura-2 with dual wavelength excitation fluorescence microscopy. Results so far indicate that gradients of Ca²⁺ are present in growing rhizoid cells but physiologically significant gradients have not yet been detected in the early stages of polarization.