Significance of Ca2+ and K+ in Micrasterias growth and morphogenesis

Abstract

Significance of Ca2+ and K+ for the complex morphogenesis of Micrasterias, which takes place through multipolar tip growth, was investigated. Studies with different external Ca2+ concentrations and Ca2+ channel inhibitors LaCl3 and verapamil indicate that Ca2+ and Ca2+ channels are essential in the development, while treatments with different K+ concentrations and K+ channel inhibitor TEA demonstrate that potassium or K+ channels are not needed in the process, albeit the existence of K+ channels. K+ is not needed even for the regulation of turgor pressure, which was found to decrease clearly during cell development. The plasma membrane ATPase inhibitors diethylstilbesterol (DES) and Na-orthovanadate stop morphogenesis and indicate the importance of ion pumps in the developmental process. Both supraoptimal, external K+ and Ca2+ cause abundant Ca2+ precipitate formation in chloroplasts, which shows that chloroplasts are important in regulation of cytoplasmic Ca2+ metabolism and that K+ activates the uptake of Ca2+ through Ca2+ channels.