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Germination experiments

Viability of seeds of different weights, belonging to five species, was analysed by examining seeds from the two extremities, and from the centres, of the individual seed weight distributions for each species. For Hypochoeris and Pimpinella, all seed weight categories exhibited >80% germinability. For Carlina and Tragopogon, heavy and medium seeds displayed >70% germinability whereas small seeds exhibited over 50% germinability. Succisa germinability fell as seed weight declined, to a value of 30-50% for the lightest seeds. Many of the lightest seeds of these calcareous grassland species are capable of germination. Initial viability of seeds of six species collected from the five countries in the Transplant consortium has also been recorded to enable comparisons of seed germination and viability properties, and loss of viability with the passage of time. Analysis of initial germinability, and germination after 7 and 19 months, under ideal storage conditions at the Millennium Seed Bank (MSB), Wakehurst Place, has allowed calculation of rates of decay in viability. These results will be shared with Workpackage 4.

An experiment was carried out to determine whether recruitment into populations of species of dry calcareous grassland is dispersal limited (i.e. limited by the ability of seeds to reach nearby but isolated sites) or access limited (limited by inability of species to establish in previously unoccupied sites). Partners from Workpackages 2-6 conducted this experiment in the UK, the Netherlands, Germany, Sweden and the Czech Republic. Four species (Tragopogon pratensis, Hypochoeris radicata, Carlina vulgaris and Succisa pratensis) were chosen for study. Seeds were collected from each of the participating countries, and used for analysis of recruitment within the country of collection.

The reason for this was to ensure maximisation of recruitment potential. Failure of recruitment could otherwise have been entirely attributable to incompatibilities between local species adaptations and environmental conditions in each country. Within each country, five permanent quadrants were established in one occupied and three unoccupied sites, and seeds were sown into these sites. The unoccupied sites were chosen as suitable sites from which each of the species was absent prior to the experiment. All unoccupied sites were grassland areas selected for increasing distance from the occupied sites. Recruitment was monitored soon after seeds were sown and also during the following spring and summer.

Studies were conducted to compare germination responses to temperature for seeds of three selected dry calcareous grassland species (Daucus carota, Succisa pratensis, Pimpinella saxifraga) collected from eight European countries (the UK, the Netherlands, Germany, Sweden, Czech Republic, Estonia, Crete and Italy). Seeds from each were sown separately onto agar plates in petri dishes at 13 temperature values, on a thermogradient plate with a constant, unidirectional temperature gradient from 9 degrees Celsius to 34 degrees Celsius. The light regime was set at 12hours light/12 hours dark. Differences have been established in speed of germination, optimum and range of germination temperatures for seeds from different provenances. Further runs of the experiment are almost analysed. Work packages 2-6 supplied WP5 with seeds for this experiment.

Differences in growth of plants grown from seeds of different provenances, under standard conditions, have been studied, using seeds of six species (Carlina vulgaris, Daucus carota, Hypochoeris radicata, Succisa pratensis, Pimpinella saxifraga and Tragopogon pratensis) from each of five European countries (the UK, the Netherlands, Germany, Sweden, the Czech Republic). Seedlings were sown into peat and grown in a greenhouse at 20±10 degrees Celsius under a 16-hour light/8 hour dark light regime. Records were made of plant height, length of longest leaf and number of leaves, at weekly intervals from week 3 until week 8 of growth, and on three occasions afterwards at five-weekly intervals.

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University of Sussex
School of Life Sciences
BN1 9QG Brighton
United Kingdom
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