Monitoring moisture in the Millennium Seed Bank
The Royal Botanic Gardens (RBG) is using a Dewmet cooled mirror dewpointmeter from Michell Instruments to monitor the equilibrium relative humidity (ERH) levels, and therefore, moisture status of seeds stored in the Millennium Seed Bank at Wakehurst Place. An important conservation and research facility, the Millennium Seed Bank will house live seeds from an anticipated 10% of the world’s plant species, enabling them to be stored long term in a state of suspended animation. Sponsored by the Millennium Commission, Orange plc and the Wellcome Trust, the Millennium Seed Bank has been established in response to the increasingly important role that seeds are playing in the conservation and use of wild plants. Extending the service offered by the RBG’s existing seed bank, the new centre will prioritise the storage of those species, mainly from the tropical drylands, that are currently under threat due to human developments and deforestation, with the final aim of collecting and preserving around 25,000 plant species by the year 2010. As a further benefit, information gleaned from analysis of the seeds will be incorporated into a comprehensive central database that, subject to agreements, will be used to publicise the contents of the seed bank to university departments, agricultural institutes and non-governmental organisations working in the developing world. In practice, seed samples collected from field trips or supplied by scientists specifically for storage, are separated from the seed cases, dried to 15% relative humidity and deep frozen for storage in air-tight aluminium and glass containers at —20°C. The low moisture content and temperatures slow down the rate at which the seeds lose their ability to germinate, preserving the species for hundreds, and in some cases, thousands of years. To ensure that the seeds remain viable during storage, conditions are carefully monitored and a number of seeds of each type are periodically extracted and tested for germination to confirm that they are still alive. Michell Instruments’ cooled mirror dewpointmeter, Dewmet, has been specially modified to provide direct analysis of the equilibration RH of the seeds samples, both prior to and during storage. Dewmet provides a high accuracy of ±0.2°C dewpoint and 0.1°C gas temperature across a measurement range of —50 °C to +85°C dewpoint and —40 °C to +90°C ambient temperature. Combined with a fast response speed of 1°C per second and zero drift, Dewmet ensures that RH readings remain accurate over time. Keith Manger, Laboratory Manager at Kew’s Seed Conservation Department comments, “The Millennium Seed Bank is an important resource in conserving the world’s plant species and offers us both an insurance service should other conservation techniques not be successful and a valuable information resource. Potentially, Dewmet also provides us with a tool for the precise measurement of seed moisture status in research studies of the role of water in seed survival.”
For further information, please contact:- Michell Instruments Limited at Nuffield Close, Cambridge, CB4 1SS. UK Tel: 0800 975 4770 Fax: 01223 434895 email:, or visit the Michell Instruments web site at July 2000 - Ref: MI180

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