Variations in seed germination of Helianthemum vesicarium and H. ventosum seeds from populations of two different altitudes in the Negev highlands, Israel

Seeds of H. vesicarium, of Irano-Turanian origin and H. ventosum, a Saharo-Arabian element, were collected from 2 elevations and tested for germination at constant temperatures from 5-40°C and at various levels of salinity at 15°C. One of the habitats was in the transition zone between the Irano-Turanian and the Saharo-Arabian regions. Here, at an altitude of 470 m, H. vesicarium grows on the northern-facing slopes and H. ventosum on southern-facing slopes. The other habitat was in the Irano-Turanian region at 920 m above sea level, in less extreme desert conditions, where the 2 species occur in the same plant community. In all cases, seeds of H. ventosum from populations at 470 m germinated faster than seeds from populations at 920 m. The same results were observed among the populations of H. vesicarium, but their germination was slower. The H. ventosum populations from the most extreme desert conditions at 470 m germinated the fastest, while H. vesicarium from 920 m germinated the slowest. The two populations of H. vesicarium differ in their flower color and seed germination properties. Flower colors are the same in H. ventosum, but their seed germination differs. -from Authors