摘要Attention is given to the role of Ca~(2+) at the interface between the cellwall and the cytoplast, especially as seen in pollen tubes. While thecytoplasm directs the synthesis and deposition of the wall, it is lesswell appreciated that the wall exerts considerable self control andinfluences activities of the cytoplasm. Ca~(2+) participates as a crucialfactor in this two way communication. In the cytoplasm, a [Ca~(2+)]above 0.1 μM, regulates myriad processes, including secretion ofcell wall components. In the cell wall Ca~(2+), at 10 μM to 10 mM, bindsnegative charges on pectins and imparts structural rigidity to thewall. The plasma membrane occupies a pivotal position betweenthese two compartments, where selective channels regulate influxof Ca~(2+), and specific carriers pump the ion back into the wall. Inaddition we draw attention to different factors, which either respondto the wall or are present in the wall, and usually generate elevatedCa~(2+)] in the cytoplasm. These factors include: (I) stretch activated channels; (ii) calmodulin; (iii) annexins;(iv) wall associated kinases; (v) oligogalacturonides; and (vi) extracellular adenosine 5'-triphosphate.Together they provide evidence for a rich and multifaceted system of communication between thecytoplast and cell wall, with Ca~(2+) as a carrier of information.