AOBPreview originally published online on January 11, 2005
Annals of Botany 2005 95(4):649-659; doi:10.1093/aob/mci060
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Annals of Botany 95/4 © Annals of Botany Company 2005; all rights reserved
Seed Germination and Seedling Emergence of Three Annuals Growing on Desert Sand Dunes in China
1 Laboratory of Intellectual Fundamentals for Environmental Studies, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan, 2 Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China and 3 Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
* For correspondence. E-mail tobe{at}nies.go.jp
Received: 11 July 2004 Returned for revision: 7 September 2004 Accepted: 1 November 2004 Published electronically: 11 January 2005
• Background and Aims Information on the initial growth characteristics of annuals found in Chinese deserts is very limited. The aim of this study was to investigate seed germination and interactive effects of irrigation and seed burial depth in sand on seedling emergence and seedling survival in three annuals (Agriophyllum squarrosum, Bassia dasyphylla and Aristida adscensionis) commonly growing on sand dunes in these regions.
• Methods Effects of temperature, light and polyethylene glycol-6000 on seed germination were examined by irrigating seeds sown on filter paper in Petri dishes. Seedling emergence was examined for seeds sown on the surface of, or at different depths (5, 10, 20, 30, 40 and 50 mm) in, sand-filled pots, which were irrigated under different regimes. For seeds buried at a depth of 50 mm, seed viability was examined after irrigation of the pots.
• Key Results Seeds of three species germinated at most temperatures recorded between spring and autumn in their native habitats. No seed dormancy was found in any species. For all three species, seedling emergence was most favoured when seeds were buried at a depth of 10 mm. When seeds sown on the sand surface were irrigated, seed germination was considerably suppressed due to water deficiency, but many seeds remained viable. For A. squarrosum and B. dasyphylla, many seeds that were deeply buried and irrigated remained ungerminated but viable, while for A. adscensionis deeply buried seeds germinated, but the seedlings did not emerge due to unfavourable seedling growth in deep sand.
• Conclusions Precipitation is the most crucial factor in determining the seasonal emergence of seedlings of the three tested species in the field. The vertical distribution of seeds in sand determines the proportion of seeds that germinate after precipitation and acts to maintain seed banks over multiple years.
Key words: Agriophyllum squarrosum, Aristida adscensionis, Bassia dasyphylla, irrigation regimes, mechanical resistance of sand, oxygen deficiency, sand hardening, seed burial depth, seedling survival, temperature effects