The seeds of many plant species are dormant at maturity and dormancy loss is a prerequisite for germination. Numerous environmental and chemical treatments are known to lessen or remove seed dormancy, but the biochemical changes that occur during this change of state are poorly understood. Several lines of research have implicated nitric oxide (NO) as a participant in this process. Here, we show that dormant seeds of Arabidopsis thaliana (L.) Heynh. will germinate following treatment with the NO donor sodium nitroprusside (SNP), cyanide (CN), nitrite or nitrate. In all cases, the NO scavenger c-PTIO effectively promotes the maintenance of seed dormancy. c-PTIO does not, however, inhibit germination of fully after-ripened seeds, and c-PTIO does not interact directly with nitrite, nitrate or CN. We also show that volatile CN effectively breaks dormancy of Arabidopsis seeds, and that CN is the volatile compound in SNP that promotes dormancy loss. Our data support the hypothesis that NO is a signaling molecule that plays an important role in the loss of seed dormancy.
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Acknowledgements This work was supported by grants to RLJ from the NSF and the College of Natural Resources, Division of Agriculture and Natural Resources, University of California and to VR from the Ministry of Education of the Czech Republic. The authors thank J.V. Jacobsen and F. Gubler, CSIRO Canberra, for the generous gift of dormant Arabidopsis seeds. Krystal Vasoya assisted with germination assays and her help is gladly acknowledged. A grant to RLJ and WR from NSF funded part of this research.