WOOD STRUCTURE OF PROSOPIS ALPATACO AND PROSOPIS-ARGENTINA GROWING UNDER DIFFERENT EDAPHIC CONDITIONS

Prosopis alpataco Phil. and P. argentina Burk. are shrubs growing unde r different ecological conditions within the Monte Desert, Argentina. Both species have similar wood structure: semi-ring-porosity, vessels with a bimodal diameter distribution, short vessel elements, paratrach eal confluent axial parenchyma, libriform fibres and homocellular rays . Prosopis alpataco has wider vessels and a greater proportion of soli tary vessels than P. argentina which has narrower vessels, mainly in c lusters, and a larger number of vessels per mm(2). The wood structure of P. argentina suggests a safer, but less efficient, water-conducting system than that of P. alpataco. This could be related to P. argentin a's tolerance to high water stress, as this species occurs mostly in s and dunes. Instead P. alpataco is a phreatophyte, getting a regular wa ter supply.