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Prosopis flexuosa and P. chilensis trees are found growing spontaneously in the arid Monte phytogeographical province of Argentina and appear to be suitable species for reafforestation of drylands and salt-affected soils. For this purpose, one of the first tasks is to study inter-and intraspecific variability through the ability of seeds to germinate under conditions of salt and moisture stress. Germination of seeds from five provenances of P. flexuosa and four provenances of P. chilensis was evaluated under water and salt stresses created by polyethyleneglycol and NaCl solutions at an isosmotic potential of -1.4 MPa.

Laboratory germination assays at 25 degrees C revealed not only significant interspecific variability, with P. flexuosa more tolerant to both kind of stress than P. chilensis, but also high variability within P. flexuosa at the provenance level, and particularly at the individual level (trees within provenances). No variability was found between provenances of P. chilensis, although variability in this species appeared at the individual tree level (intraprovenance variation).

The ability shown by seeds from some provenances and/or individual trees of both species to germinate under stress conditions created in this study indicates that there are sufficient intraspecific variations for the purpose of selection. (C) 1998 Academic Press.