Gum exudation in South-American species of Prosopis L. (Mimosaceae)

Prosopis species exude a water-soluble gum that has been used as a substitute for arabic gum. The objective of this work was to evaluate the occurrence of natural gum exudation in seven South-American species of Prosopis and the productivity of induced-gum exudation. Natural exudates were found in three species: P. flexuosa, P. chilensis and P. nigra. In the latter two, exudates were dark, liquid and bitter, while in P. flexuosa, up to 1.6 kg tree−1 of amber-clear gum was harvested. High-productive trees were old, with very little vegetative growth and were growing on sandy soils. In order to induce gum exudation, trees were wounded. Wounds exuded copiously during 7 months. Exudation increased during late Summer and Fall, after fruits were ripen.