Abstract
Achillea fragrantissima and Moringa peregrina are dominant plants in the mountainous desert of Saudi Arabia. The two species suffer from intensive anthropogenic pressures as they have important medicinal uses. This paper aimed to evaluate the effect of temperature and salinity on germination of A. fragrantissima and M. peregrina in order to provide information about germination requirements which could be useful for conservation. To this end, seeds of both species were germinated at different constant (5, 15, 25 and 35 degrees C) and alternating temperatures (5/15, 10/20, 15/25, and 25/35 degrees C). Moreover, seeds were germinated under different NaCl concentrations (0, 1000, 2000, 3000, 4000 and 5000 p.p.m.). At both constant and alternating temperatures, seed germination of both species was significantly different among different incubation temperatures. At constant temperature, germination percentage of A. fragrantissima and M. peregrina was maximum (67.7 and 83.0%, respectively) at 25 degrees C, while at alternating temperatures, the optimal germination (81.0%) of A. fragrantissima occurred at 15/25 degrees C, and for M. peregrine, it (95.3%) was at 25/35 degrees C. Germination at alternating temperatures is higher than at constant temperatures. Germination of M. peregrina occurred at higher temperatures when compared to that of A. fragrantissima. Salinity showed significant inhibitory effect on seed germination of the two species. Germination of A. fragrantissima seeds was more sensitive to salinity than M. peregrina. Maximum seed germination of both species occurred in distilled water, and then germination percentage decreased with increasing NaCl concentration. The lowest germination percentage occurred at 5000 p.p.m. (15.3 and 60.7% for A. fragrantissma and M. peregrina, respectively).