Phospholipase D (PLD) was first discovered in plants. It plays an important role in the regulation of cell functions not only in plants, but also in animal systems. It is interesting from the aspect of its dominant position in the signalling transduction processes. It controls the utilization of the membrane phospholipids for specific intentions--products of its catalytic activity are involved in intracellular communication processes. The study of the cell-regulation-system shows that PLD is a part of lipid-based signalling via octadecanoid pathway, which leads to the production of jasmonic acid, the basic signalling molecule in plants. PLD-mediated hydrolysis of the membrane phospholipids posed this enzyme into the level of the transmembrane and cell signalling participant. This area is interesting in the aspect of the production of biologically active compounds in plants. Because the signal-regulated synthesis of some secondary metabolites by the lipid signalling pathway has been already shown (induction of the gene expression coding the biosynthetic enzymes of flavonoids and terpenoids), the area of PLD study is perspective. This article is orientated on plant PLD and gives a basic review of its biochemical and molecular-biological properties (enzymology, molecular structure, subcellular localization, isoenzymes) and its physiological functions on the cell level (lipid signalling pathway, phospholipid degradation, phytohormones and cell signalling, growth, development and cell ageing, membrane remodeling).