Dormancy and germination strategies of a desert winter annual Echinops gmelini Turcz. in a temperate desert of China

Echinops gmelini Turcz. is an annual Asteraceae species widely distributed in the desert habitats of northern China. However, little is known about how this species adapts to harsh desert habitats. In this study, E. gmelini germination behaviors were observed in a natural population at the southeastern edge of the Tengger Desert. In addition, the effects of temperature, light, hydration-dehydration (H-D) cycles and different storage conditions on seed germination were tested in the laboratory. E. gmelini behaves as a winter annual, and its seeds germinate during the summer and early autumn in the field. Fresh seeds have non-deep physiological dormancy (PD). A 15-day dry storage treatment under laboratory conditions was required to break PD. Non-dormant seeds can germinate rapidly and at a high rate in light at 30/20 degrees C. Dry storage with seasonal temperature changes had little effect on seed germination and dormancy. However, under natural field conditions, greater and faster germination at a wide range of temperatures was observed after seeds were stored for 1-2 months, which allows seeds to germinate during short periods of moisture availability; seeds were induced into secondary dormancy after storage for 3 months which may prevent germination in autumn. Furthermore, seed germination was reduced and became faster after exposure to four or more H-D cycles. Our results suggest that precipitation is the key factor in determining E. gmelini seed germination time in natural habitats, and they provide information about the strategies that annual plants need to adapt to climatically unpredictable environments in temperate deserts.