Germination characteristics of shingle beach species, effects of seed ageing and their implications for vegetation restoration

Published source details Walmsley C.A. & Davy A.J. (1997) Germination characteristics of shingle beach species, effects of seed ageing and their implications for vegetation restoration. Journal of Applied Ecology, 34, 131-142.
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Summary

Major disturbance associated with construction of a power station between 1987-1994 necessitated restoration of coastal-shingle vegetation at a site in eastern England. As part of and underpinning this project, an investigation was undertaken into the germination ecology of six key herbaceous plant species: sea kale Crambe maritime, sea holly Eryngium maritimum, yellow horned-poppy Glaucium flavum, sea sandwort Honckenya peploides, sea pea Lathyrus japonicus and curled dock Rumex crispus. The use of indigenous seed, collected from the site before the 6-year construction project, necessitated long-term storage. The effects of seed ageing on viability and germination responses to temperature, light and salinity were examined to determine how any reduction in germination might be mitigated.

Seed collection and storage: Ripe seed of six species (sea kale Crambe maritime, sea holly Eryngium maritimum, yellow horned-poppy Glaucium flavum, sea sandwort Honckenya peploides, sea pea Lathyrus japonicus and curled dock Rumex crispus) was collected between 10 July and 11 October 1986, and 21 August and 30 September 1992 from 1.5 km of shingle beach at Sizewell on the Suffolk coast, eastern England (National Grid ref. TM 475 635).

Seed was stored in paper bags, dried at room temperature for 5-13 weeks, then thresed and cleaned. Seed was then placed in paper envelopes stored in darkness over silica gel in air tight plastic containers at around 2°C.

Seed viability and germination: Changes in seed viability were tested annually from 1987-1990 and in 1993 using tetrazolium tests. The effects of stratification on germination were also examined between March-June 1993, and experiments on the effect of seed age, dormancy temperature and salinity on germination were undertaken in July and August 1993 using seed collected in 1986 and 1992.

Longevity: Storage reduced germination rate in five of the six species, the exception being R. crispus. Despite this, a substantial proportion of seed remained viable after 7 years storage for all except E.maritimum. Ageing resulted in considerably less germination at higher temperatures in some species. Salinity-enforced dormancy was significantly greater in aged seed for four of the species. The promotion of germination by light in H.peploides disappeared with age. These changes represented a narrowing of the environmental conditions that allow germination, even when viability only declined slightly.

Dormancy: Innate seed dormancy was important in all species except R.crispus. C.maritima and L.japonicus showed hard-seed dormancy. Stratification of E.maritimum, G.flavum and H.peploides effectively softened the pericarp or testa, and satisfied their varying requirements for low temperature to overcome physiological dormancy.

Seed storage at low temperature and humidity for 7 years did not affect innate dormancy, except in H.peploides, where the requirement for stratification was lost.

Germination: All species germinated well in diurnally alternating temperature regimes. Germination of H.peploides was promoted by light, but the other species were light insensitive. Increasing salinity progressively reduced germination rate relative to that in distilled water, and sea water at concentrations of 50% or more completely inhibited germination.

Conclusions: Innate dormancy among the six shingle species tested, and the use of stored seed, with high viability, but stringent germination requirements, are likely to result in poor and erratic germination. The use of appropriate pretreatments discovered during this study to overcome dormancy, and identifying optimal conditions for germination should allow the efficient use of seed for plant production in restoration projects such as that undertaken at Sizewell.

Note: If using or referring to this published study please read and quote the original paper, this can be viewed at: http://www.jstor.org/view/00218901/di996081/99p0190k/0