AOBPreview originally published online on January 9, 2009
Annals of Botany 2009 103(5):785-794; doi:10.1093/aob/mcn254
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Post-abscission, pre-dispersal seeds of Digitalis purpurea remain in a developmental state that is not terminated by desiccation ex planta
1 Seed Conservation Department, Royal Botanic Gardens Kew, Wakehurst Place, Ardingly, West Sussex RH17 6TN, UK
2 Department of Agriculture, University of Reading, Earley Gate, PO Box 237, Reading RG6 6AR, UK
* For correspondence. E-mail f.hay{at}kew.org
Received: 5 September 2008 Returned for revision: 20 October 2008 Accepted: 19 November 2008 Published electronically: 9 January 2009
Background and Aims: Seed quality may be compromised if seeds are harvested before natural dispersal (shedding). It has been shown previously that slow or delayed drying can increase potential quality compared with immediate rapid drying. This study set out to investigate whether or not there is a critical moisture content, below which drying terminates maturation events for seeds harvested after mass maturity but before dispersal.
Methods: Seeds of foxglove (Digitalis purpurea) in the post-abscission pre-dispersal phase were held at between 15 and 95 % RH for 4 or 8 d, with or without re-hydration to 95 % RH for a further 4 d, before drying to equilibrium at 15 % RH. In addition, dry seeds were primed for 48 h at –1 MPa. Subsequent seed longevity was assessed at 60 % RH and 45 °C.
Key Results: Rate of germination and longevity were improved by holding seeds at a wide range of humidities after harvest. Longevity was further improved by re-hydration at 95 % RH. Priming improved the longevity of the seeds dried immediately after harvest, but not of those first held at 95 % RH for 8 d prior to drying.
Conclusions: Maturation continued ex planta in these post-abscission, pre-dispersal seeds of D. purpurea dried at 15–80 % RH at a rate correlated positively with RH (cf. ageing of mature seeds). Subsequent re-hydration at 95 % RH enabled a further improvement in quality. Priming seeds initially stored air-dry for 3 months also allowed maturation events to resume. However, once individual seeds within the population had reached maximum longevity, priming had a negative impact on their subsequent survival.
Key words: Digitalis purpurea, seed development, post-harvest treatment, priming, longevity, ex situ conservation
Present address: Warwick HRI, Wellesbourne, Warwick, CV35 9EF, UK
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  L. H. Butler, F. R. Hay, R. H. Ellis, R. D. Smith, and T. B. Murray Priming and re-drying improve the survival of mature seeds of Digitalis purpurea during storage Ann. Bot., March 21, 2009; (2009) mcp059v1. [Abstract] [Full Text] [PDF]
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