The effect of temperature on seed germination in three common bulbous plants of different habitats in the Central Negev Desert of Israel

Seeds of three bulbous plant species of the Negev Desert of Israel were germinated in 10, 15, 20 and 25°C, which are temperatures commonly occurring in their natural habitats in winter when seed germination takes place. Germination rates and percentages correlated with their habitat distribution: Bellevalia desertorum, the most thermophilous species, germinated better and faster than the other species in all temperatures. The least thermophilous of the three, Tulipa systola, germinated very poorly in 20 and 25°C, while the intermediate B. eigii did very poorly in 25°C. Germination rates of the three species correlated with the maximum soil temperatures in the top 2-cm layer of the soil, and with the rate of drying of this soil layer in their respective habitats, as was measured one week after rainfall. High winter temperatures on south-facing slopes, B. desetorrum's habitat, and the associated rapid desiccation of the soil crust, may exclude T. systola and B. eigii from this habitat. However, low temperature is not a dominant factor causing the absence of B. desertorum or B. eigii from the coolest habitat, inhabited only by T. systola.