TEMPERATURE EFFECTS ON GERMINATION OF PROSOPIS-ARGENTINA AND PROSOPIS-ALPATACO (FABACEAE, MIMOSOIDEAE)

P. argentina and P. alpataco are shrub species that occupy areas with different soil characteristics within the arid zone of Argentina. The objective of this work was to determine the germination response to di fferent temperature of seeds of both species, and other seed character istics affecting the germination process. Under controlled conditions, daily and final germination percentages, germination rate, and seedli ng vigour were determined. The following temperatures were tested: 10, 15, 20, 25, 30, 35, 30 and 45 degrees C. The mean seed M eight and th e two greatest seed diameters were registered. For both species. the o ptimum germination temperature was 35 degrees C, the minimum temperatu re was 15 degrees C, and the maximum was 40 degrees C. P. alpataco sho wed final yermination percentages higher than those of P. argentina at 15 degrees C. Although the optimum germination temperature for P. alp ataco was 35 degrees C, seedlings showed their maximum root growth bet ween 25 degrees C and 35 degrees C. It appears that P. alpataco would be capable of establishing itself within a wider range of temperature than P. argentina. P. argentina seeds are larger and heavier than thos e of P. alpataco, although no relationship between seed size and seedl ing vigour was observed in this study. Water uptake kinetics was also analysed. It showed two well defined phases, one of imbibition and the other one of visible germination. The stationary phase was either non -existent or very short.