In Vitro Culture of Prosopis Species

Abstract

The northern part of Chile (Lat. 18 – 27°South) has one of the most extreme desert climates in the world. The region is characteri zed by an almost complete lack of rainfall, i.e., not more than about 1 mm per year is registered. Although practically no vegetation is found in the desert called Pampa del Tamarugal, located between southern Lats. 19° to 22°, the endemic Prosopis tamarugo tree, (family Mimosaceae), grows naturally in some areas of this desert. Within the last 30 years about 20.000 ha of mesquite have been planted. Of these approximately 14.000 ha were planted with P. tamarugo(4), 3.000 ha with P. alba and P. flexuosa (24) and 400 ha with mixed populations. Besides these stands there are older ones planted with P. tamarugo which cover an additional 3.200 ha. Controversy exists regarding the relationship between water supply and xeromorphic adaptations (13,20,27). It has been suggested that water can be absorbed from the atmosphere and translocated to the roots under certain conditions (26,30). On the other hand, the deep-reaching root system, going sometimes down to 15 m and more, absorbs freatic water moving underground from the Altiplano regions. In some areas the trees also obtain water from seasonal floods that run down from the mountains. In addition to water stress resistance, Prosopis trees show a high tolerance to salts. Salts accumulate as crusts upon the soil surface or lower horizons (caliche deposits) as a result of cristalization during water evaporation.