title: Seed dormancy-breaking in a cold desert shrub in relation to sand temperature and moisture.
abstract: Seasonal periodicity of seed germination and its relationship to seasonal changes in temperature and soil moisture have been well studied in seeds of species with physiological dormancy. However, relatively little information is available on the role of these environmental factors in controlling germination of seeds with physical dormancy (PY). Our primary aim was to determine if seeds of the cold desert sand dune semi-shrub Eremosparton songoricum exhibits seasonal periodicity of seed germination and the relationship between seed dormancy break and soil temperature and moisture. In the laboratory, seeds incubated on dry, wet, wet-dry and dry-wet sand were exposed to a 1-year sequence of temperature regimes simulating those in the field. In the field, seeds were buried at different depths on a sand dune, and germination of periodically exhumed seeds was tested at five temperature regimes during a 2-year period. In the one-year sequence of simulated natural temperature regimes, breaking of PY was more effective under constantly wet than under constantly dry conditions, and germination percentage was significantly higher under dry-wet than under wet-dry conditions. Seeds buried in the field exhibited a distinct peak of germination in spring and little or no germination in other seasons. The final (two-year) monthly cumulative germination percentage differed among burial depths and temperature, and it was highest (47%) in seeds buried at 3 cm and tested at 25/10 °C. A seed cohort of E. songoricum likely exhibits a long-term annual periodicity of spring germination in the field, and dormancy break appears to be driven by low (winter) temperatures and relatively high sand moisture content. To our knowledge this is the first study to document seasonal periodicity in seed germination in a cold desert species with PY and to identify the mechanism (at the whole-seed level) of its occurrence.
authors.affiliation: Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urümqi 830011, China.|Turpan Eremophytes Botanical Garden, Chinese Academy of Sciences, Turpan 838008,China.
authors.forename: Huiliang
authors.initials: H
authors.lastname: Liu
authors.affiliation: Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urümqi 830011, China.|Xinjiang Institute of Science and Technology (Aksu Campus), Aksu, 843000, China.
authors.forename: Buhailiqiemu
authors.initials: B
authors.lastname: Abudureheman
authors.affiliation: College of Grassland and Environment Sciences, Xinjiang Agricultural University, Xinjiang Key Laboratory of Soil and Plant Ecological Processes, Urümqi 830052, China.
authors.forename: Lingwei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY40506, USA.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY40506, USA.|Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY40546, USA.
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.affiliation: Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urümqi 830011, China. zhangdy@ms.xjb.ac.cn.|Turpan Eremophytes Botanical Garden, Chinese Academy of Sciences, Turpan 838008,China.
authors.forename: Daoyuan
authors.initials: D
authors.lastname: Zhang
keywords: Burial depth; Eremosparton songoricum; Fabaceae; physical dormancy; seed germination phenology; wet-dry cycles.