Cell sap

Discovery

Antonie van Leeuwenhoek described the plant vacuole in 1676. Contractile vacuoles ("stars") were first observed by Spallanzani (1776) in protozoa, although they were mistaken for respiratory organs. Dujardin (1841) named these "stars" as vacuoles. In 1842, Schleiden applied the term for plant cells, to distinguish the structure with cell sap from the rest of the protoplasm. In 1885, de Vries named the vacuole membrane as tonoplast. Christian de Duve discovered mammalian lysosomes using biochemical methods in the mid-1970s. De Duve named lysosomes based on their biochemical properties (from the Greek lysis – digestive and soma – body). Their physical form was confirmed shortly afterward by electron microscopy. Because the lysosome shares many properties with vacuoles across taxonomical kingdoms, the notion that vacuoles and lysosomes are distinctly different organelles is more historical than functional.