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How does autoradiography show where radioactive substances are concentrated in tissue?
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Morphology
Common leaf morphologies.
Autoradiography identifies the concentration of radioactive substances in biological tissue by placing the specimen in direct contact with a photographic emulsion.12
The process works as follows:
- Exposure: Radioactive isotopes introduced into the plant or animal system emit radiation from within the tissue.1
- Interaction: As charged particles or electrons from these substances pass through the photographic emulsion, they interact with silver halide molecules suspended in the gelatin matrix.3
- Latent Image: These interactions create an "excited" state in the molecules, forming a latent record of the radiation exposure.3
- Development: Through a chemical development process, the grains containing excited molecules are converted into metallic silver. This process amplifies the signal, making the areas of high radioactivity visible as a darkening on the film or plate.3
By observing this developed image, researchers can precisely map the distribution and concentration of radioactive materials within the histological specimen.12