Seed Germination Of Three Native Shrubs In Urumqi

Atraphaxis spinosa, A. virgata and Convolvulus tragacanthoides are native shrubs in Urumqi which have potential value in vegetation restoration. The germination, dormancy and germination phenology characteristics of them were observed and analyzed both in field and indoors, and the ecological adaptive germinative strategy of the species was discussed. The main results are as follows:The seed germination of the shrubs differ singnificantly in temperature, water stress and salt stress. The optimal germination temperature was 30/20℃for A. spinosa, 20/10℃and 30/20℃for A. virgata, respectively. The germination percentages of C. tragacanthoides are not significant in alternating temperature regimes from 10/6℃to 30/20℃. The seeds can germinate at -2.7MPa of water stress and 0.5mol/L of salt stress. PEG solution of -0.3MPa promoted seed germination of the Atraphaxis species. Salt stress hardly inhibit seed germination of C. tragacanthoides.The dormancy characteristic of the seeds are different. Dormancy break of Atraphaxis spinosa and A. virgata seeds by cold stratification at 5℃for 8 weeks and 6 weeks, also at the habitat in winter. The seeds of the Atraphaxis species were shallow non-deep physiological dormancy. The seeds of C. tragacanthoides were physical dormancy, because the dormancy was broken by scarification.The seeds were treated by dry storage at room temperature, dry storage at 5℃and burying storage for 9 months. The seed germination of the Atraphaxis species achived higher after dry storage at room temperature than that of at 5℃, in opposition to C. tragacanthoides. The Atraphaxis species seeds all germinated after buried. And the seeds of C. tragacanthoides had lower germination after buried.Two Atraphaxis species have different mechanisms of germination. Their seeds have different level of dormancy. A. spinosa fruits twice a year, in June and September. A. virgata has a long florescence last out two months. A. spinosa seeds were collected in June and September, while A. virgata were collected in October and November. The seeds of A. spinosa maturating earlier have higher germination comparing to matured later. Dry storage significantly increased germination percentage of A. virgata at 15/6℃, the percentage of increment was greater in October than that in November. A. spinosa seeds matured in October were break dormancy after 9 months and the seeds matured in November after 6 months in the situation of dry storage.Germination phenology of the seeds are different due to the dormancy types. No seedlings emerged after sowing of two Atraphaxis species seeds. In the next spring, the seedlings were recorded. The seeds of C. tragacanthoides emerged after sowing, and continued to germinate in April the next year.The seed germination, dormancy and germination phenology characteristics of the shrubs have significant ecological consequences in development of seedling, population persistence and expansion in desert around Urumqi.