LOW-MOLECULAR-WEIGHT SOLUTES IN DESICCATED AND ABA-TREATED CALLI AND LEAVES OF CRATEROSTIGMA-PLANTAGINEUM

Craterostigma plantagineum, a resurrection plant, displays extreme desiccation tolerance; dehydrated leaves and ABA-treated calli resume a normal metabolic state upon rehydration. Samples of calli and leaves of C. plantagineum were analysed for the major classes of compounds such as sugars, fatty acids, amino acids and derivatives, and phytosterols. Calli solutes are characterized by large amounts of glutamine and tyramine, triterpene acids and colneleic acid, an inhibitor of lipoxygenase. Among the sugars extracted from calli, sucrose, together with its hydrolytic products, predominates, while maslinic, ursolic and oleanolic acids are the most important triterpenes. In leaves the most common triterpene alcohols were campesterol, stigmasterol and beta-sitosterol. Almost 50% of the weight of the lyophilized material consisted of 2-octulose, a sugar present as a minor component in a limited spectrum of plant species. Acquisition of desiccation tolerance in ABA-treated and desiccated calli was accompanied by an increase of fatty acids, accumulation of colneleic acid and by the disappearance of glucose and fructose. The most relevant biochemical effect of desiccation on leaves was the conversion of 2-octulose into sucrose.