Probing the distribution of plant hormones by immunocytochemistry

Taking advantage of the highly specific structural requirements of antibodi es for binding, the detection of plant hormones in tissue by immunolocalisa tion offers a powerful tool to study the distribution of these signalling m olecules. For instance, specific monoclonal and polyclonal antibodies have been raised for abscisic acid, indole-3-acetic acid and a variety of cytoki nins. Immobilisation by chemical fixation or freezing minimises diffusion o f these low molecular weight compounds in plant tissues. Associated primary antibodies in sections or permeabilised cells can be detected by secondary antibodies linked to enzymes, fluorescent molecules or electron opaque mar kers, which allow detection by either light or electron microscopy. These t echniques have already found their application in various studies related t o the physiology of these plant hormones.