Germfree Plants, Cultivation of

the growing of plants in an environment in which microorganisms are completely absent or, more commonly, are absent only at the roots. An entire plant may be cultivated germfree only in a closed vessel, where it is difficult to maintain the air, light, and temperature conditions essential for aerial organs.

Germfree plants are cultivated in order to study the absorption and assimilation of minerals and organic matter, the role of microorganisms in the nutrition and vital activities of plants, and the participation of the root system in metabolism. The plants are grown in water, sand, or soil, depending on the purposes of the investigation. Vessels filled with water, sand, or soil to which a nutrient mixture is added are usually sterilized in an autoclave. The solutions of organic matter added to the nutrient mixture are sterilized without heating (to prevent them from decomposing) by passing them through fine-pore Pasteur-Chamberland filters and Seitz asbestos-cellulose filters. The seeds used in the cultivation of germfree plants are treated in special sterilizers with a bromine solution, hydrogen peroxide, or concentrated sulfuric acid (used to treat seeds with hard coats.)