In vitro culture as a potential method for the conservation of endangered plants possessing crassulacean acid metabolism

Rare and endangered plants possessing crassulacean acid metabolism (CAM), s uch as cacti, usually present limited reproductive capacities and very slow growth rates. The use of in vitro culture can overcome these difficulties. The massive in vitro production of new propagules which result in totally regenerated plants is described for two endangered cacti, Obregonia denegri i Fric. and Coryphantha minima Baird. A comparison of in vitro and ex vitro growth rates demonstrated that the in vitro environment notably accelerate s cacti growth. Malic acid titratable acidity indicated that increase of th e net carbon dioxide uptake is associated with active growth. This might be related to particular factors of the in vitro environment such as the high relative humidity inside the culture vessels, or growth regulators supplem ented to the growth media. In vitro-derived cacti showed a proficient re-es tablishment capability which could be related to their succulence since wat er loss during transplantation did not represent a crucial hydric stress. S ucculence and plasticity of the CAM metabolic pathway in plants Like cactus , represent some possible advantageous for the application of in vitro prop agation techniques in a number of endangered, succulent plants like members of the Cactaceae, Agavaceae, Orchidaceae, or Bromeliaceae families. (C) 19 99 Elsevier Science B.V. All rights reserved.