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Comparative Longevity (Orthodox Seeds)

Standard seed ageing protocol equipment

This project is one of series in the theme of Preservation Technology.

It is well known that seeds from different species show wide variation in longevity during dry-storage. In the seed bank, where seeds are stored at -20°C after drying to 15%RH at 15°C, seeds from some species may remain viable for hundreds of years whereas seeds from other species may only survive a few years at best. This has implications for the management of the collections e.g. how often re-testing should be carried out, and perhaps in deciding whether conventional seed banking is an appropriate method of conservation for some, extremely short-lived species.

This comparative longevity screen has been running for a number of years. For collections with large numbers of seeds, a sample of 600 is removed from storage and aged at 60% RH and 45°C; samples are taken at regular intervals and a germination test carried out. Probit analysis is carried out on the germination data in order to model the survival curve and rank the species according to the relative longevity.

By May 2005, seeds from more than 200 collections representing 155 species from 55 families have been included in the screen and an analysis of comparative longevity in relation to factors such as ecology, seed structure and climate of origin has been carried out and presented at an international conference. Additional data for species from the humid tropics and cold, dry temperate areas will enable phylogenetically independent contrasts (PICS) analysis and publication of a new predictive model for seed longevity in 2006/7.

The project is also focusing within smaller taxonomic groupings in order to consider variation in longevity within families, genera, and species (e.g. looking at the effects of growing conditions on subsequent longevity), particularly those which appear to be particularly short-lived. Comparative studies within the Ranunculus, Rhododendron, and Silene genera have already been carried out.

A standard ageing protocol for comparative longevity studies has been published as an information sheet on the world wide web, and the method has been adopted by at least four international partners with whom we are collaborating.

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