Calcium in plants: an important element of cell physiology and structure, signaling, and stress responses

Abstract

Calcium ions (Ca²⁺) are absorbed from the soil by the root cells before being distributed throughout the plant. The transport of Ca²⁺ to aboveground parts relies on the movement of xylem, which is influenced by the transpiration rate of individual organs. The final distribution of Ca²⁺ in tissues and cells depends on the effective function of channels and transporters that facilitate Ca²⁺ movement through plasma and specific intracellular membranes. Local fluctuations in free Ca²⁺ concentrations serve as a mechanism to elicit cellular responses, characterized by distinct calcium signatures, or to enable long-distance signaling in a cell-to-cell network. The specificity of individual Ca²⁺ transport proteins is primarily determined through studies in plants with induced changes in the expression of these proteins. Concurrently, it is recognized that plant cells contain significant reserves of Ca²⁺ both in the labile and in the permanently bound states, which influences various aspects such as biomechanical properties or the defensive capabilities of the cells. The diverse roles of Ca²⁺ in plant cells highlight the importance of a thorough understanding of Ca²⁺ metabolism.