UK Germination Toolbox - about the database
The Millennium Seed Bank Partnership has successfully collected and stored seed samples from around 90% of the United Kingdom’s native seed plant species, as a hedge against extinction and as a conservation resource. The ‘missing’ species produce either no seeds at all; or seeds that cannot be stored conventionally; or are too rare, or fruit too infrequently for seed collections to have been made without threatening their survival. As well as further collecting to increase bio-geographic and genetic coverage of those species already in the bank, efforts are also continuing, to locate and bank collectable samples from those last few, elusive species.
In this database, the naming and definition of UK native species follows the PLANTATT database (Hill, Preston and Roy, 2004); and includes species designated there as native (N), native endemic (NE) or archaeophyte (AR; introduced before 1500AD) – 1442 species. At present casuals, aliens and more recent introductions are not included.
Germination tests are central to the routine management of seeds collected for the purpose of their conservation. As well as being the most useful means of monitoring seed viability over time in storage; they also provide essential information towards the propagation of new plants. Ultimately, seeds in a bank, even though they may be perfectly viable, will be of little use if we do not know how to grow new plants from them.
The MSBP aims to promote conservation by enabling the sustainable use of seeds in the bank, not least for the re-introduction of native species and restoration of degraded natural and semi-natural vegetation. Consequently, this database is intended as a resource for all those who need to propagate UK native species from seed: researchers; conservationists attempting to restore native species and vegetation; horticulturalists, including those commercial nurseries specialising in growing and supplying UK native species. It will also be useful for researchers in comparative and evolutionary ecology, seeking germination trait data. The ‘toolbox’ is comprised of information on germination from up to three available sources.
1. MSB germination tests
The main purpose of this database is to share the MSB’s germination data on UK species with potential users. So, wherever they are available, a search returns a summary of the conditions applied in successful MSB germination tests.
By and large the conditions (mostly temperatures) returned by a search for a particular species will be those that resulted in at least 75% germination (i.e. the MSB viability standard is passed). The tests ‘accepted’ by the MSB are usually those that are easiest to apply and repeat; wherever possible avoiding complicated temperature regimes, or the application of dormancy-breaking chemicals, for example.
Please note that the successful germination conditions presented almost always DO NOT result from designed experiments with controls. Thus, they do not exclude other potentially equally successful conditions that have not been tried; nor are unsuccessful conditions reported at present. In a few cases the successful germination conditions result from tests on collections of species native to the UK, but originating elsewhere, usually in Europe.
2. Information from published literature
Despite the MSB’s high coverage of UK native species, successful germination conditions are not yet available for some of them. This is sometimes due to as yet intractable dormancy problems in certain species – and research continues on these. More frequently, the collections currently held of those species are too small (<500 seeds) to commit any of them to germination testing, without jeopardising the value of the conservation collection.
In such cases, where there is published information available, the database will return a summary of the conditions found to be successful in other laboratories. This part of the database currently relies heavily on the extensive compilation and analysis of published literature by Baskin & Baskin (1998), with further updates to 2001 kindly provided by the authors (cf. Baskin & Baskin, 2003a). Updates beyond that date are from the MSB’s own literature searches, which are ongoing, and will be added to the database in due course. Some published germination treatments for UK native species is for material not collected in the UK.
3. Predicting likely successful temperature regimes
Worldwide, around one third of all wild species studied are not exacting in their germination requirements; and this is probably also true of UK species. So long as they have sufficient moisture and a broadly favourable temperature, they are relatively easy to germinate fully. The remainder possess varying degrees of several different kinds of dormancy, presumed to result from evolution to ensure that seedlings emerge when they are most likely to survive, and often also to ensure that emergence is spread over time (‘bet hedging’). Synchronous germination to a high percentage is often quite difficult to achieve for these species. However, optimal germination temperature and dormancy breaking conditions are often related to local climatic conditions; and these can suggest likely successful germination conditions.
For example; seeds of tropical dry-land species, shed at the beginning of the dry season, often require an extended period of relatively high temperature in the dry state before germination occurs in the subsequent rainy season. This requirement appears to be an adaptation to avoid germination in response to sporadic, unreliable rainfall during the dry season, when emerging seedlings would probably be killed by drought. Similarly, cool temperate species shed in autumn may delay germination until temperatures begin to rise in the early spring, by having a requirement for an extended period at low temperature (‘cold stratification’) before germination can occur, mimicking the passage of winter and the risk of frost damage to sensitive seedlings.
Application of temperature regimes related to seasonal climate cycles forms the basis of ‘move-along’ experiments (e.g., Baskin & Baskin, 2003b); in which seeds, imbibed on a moist substrate, are transferred between a succession of incubators, running at temperatures that approximate to local conditions at the source of the seeds. The start point in the temperature regime is set at the conditions pertaining when seeds are shed naturally (≈ collected) in the field.
To help users predict likely successful temperature sequences, they are able to enter the latitude and longitude of the source of their seed collection (if known; input restricted to decimal degrees at present), as well as month of collection. The system will return the monthly mean minimum and maximum as well as corresponding median temperatures. This facility is mainly to allow users to make predictions of likely germination conditions in the absence of information from MSB germination tests MSB. However, they can also be used in conjunction with MSB records and published data, where they exist.
The temperature values are provided by ‘WORLDCLIM’ (Hijmans et al., 2005); which uses an algorithm to compute interpolated, or modelled, temperature and rainfall data from real data compiled from weather station records worldwide, at high (1km) spatial resolution. Properties of the algorithm and uneven distribution of climate stations mean that uncertainty is highest for small islands and mountainous regions.
The database currently does not return interpolated monthly rainfall amounts for UK locations, as rainfall appears to have very limited value in predicting germination period in the UK. Especially in seasonal climates, rainfall amounts can give an indication of relatively dry periods (when germination would be less likely); or relatively moist periods, when seedling emergence is likely to take place in the field. Rainfall is more evenly distributed throughout the year in the UK; and though observed mostly in spring and autumn, newly emerged seedlings of some species can be seen at any time of the year, even during mild weather in winter. Worldwide, observations of species’ seedling emergence timing are scarce or mostly non-existent; whereas it is often quite well documented for UK species (e.g. ECOFLORA).
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