Carbon and Energy Source - The most preferred carbon source in plant tissue culture is sucrose. Glucose supports equally good growth while fructose is less efficient. Sucrose, while autoclaving the medium, is converted into glucose and fructose. In the process, first glucose is used and then fructose. Other carbohydrates, such as lactose, galactose, rafinose, maltose, cellobiose, melibiose, and trehalose, generally yield inferior results. Tissue cultures of Sequoia and maize endosperm can even metabolize starch as the sole carbon source.
Plant cells and tissues in the culture medium lack autotrophic ability and therefore need external carbon for energy. Even tissues which are initially green or acquire green pigments under special conditions during the culture period are not autotrophs for carbon. The addition of an external carbon source to the medium enhances proliferation of cells and regeneration of green shoots.