A seed bank plans to store a barley seed lot as an active collection at 5°C. The initial viability is 99.5% and the collection has been dried to 10% moisture content. When will viability have fallen to the regeneration standard of 85%?
That comes from a little set of exercises that staff of Kew’s Millennium Seed Bank use on the training courses on seed handling and conservation that they frequently organize around the world. Time was when you had to slog through the maths to answer that question by hand. Want to try? Here’s the equation, go for it:
Nowadays, of course, there’s an app for that. Or at least a website, SID, Kew’s Seed Information Database. ((Royal Botanic Gardens Kew. (2008) Seed Information Database (SID). Version 7.1. Available from: http://data.kew.org/sid/ (May 2008).)) Just click on Predict storage time, select Hordeum vulgare, enter storage temperature, equilibrium moisture content, initial viability and final viability, and click Calculate. Hopefully you got about 18 years. Easy, no?
Ok, smartypants, so now try this.
You are a forest extension officer working with communities in Burkina Faso to collect and plant Khaya senegalensis, a multipurpose tree species, with a seed oil content of 67%. Seeds are shed during the month of May at an eRH of around 50%. Average climatic conditions in the afternoon in May are 38°C and 40%RH. You use ambient drying during the afternoon to reduce eRH to 40% and then store seeds at ambient temperature (12 month average: 29°C) in large plastic drums. An initial germination test shows that viability is 99%. What will the viability be after 12 months storage under these conditions?