Survival of Legume Seeds
The legumes are a diverse and economically important family with some species being major crops vital to human nutrition. Scientific research into the seed traits of grain legumes and their wild relatives is a significant part of Kew’s seed research programme.
The MSBP (Millennium Seed Bank Partnership) has developed collaborative projects in several areas of high legume biodiversity, in particular the drylands of South America and Africa. Since 2006, the seeds of 2,191 species have been added to the MSBP collections and to date, approximately 10% of the species housed in the Millennium Seed Bank are legumes.
In 2006, a wallet with seeds was found among the papers of the Dutch merchant, Jan Teerlink. The seeds had been collected in the Cape region of South Africa, where a Dutch East India Company had its own botanic gardens. On its return journey from the Cape of Good Hope Teerlink’s ship, the Henrietta, was captured by British ‘privateers’ and the seeds transferred to the Tower of London in 1803. Two hundred years later, scientists from Kew were able to germinate the seeds of three species including two legumes (Daws et al. 2007). Such extreme seed survival under less than ideal storage conditions means that seeds stored under optimal conditions may live for hundreds of years.
To assess if seeds remain viable during storage, viability markers are being developed. Using legumes, Birtić et al. (2006) found that viability loss during seed ageing correlates with changes in cellular redox potential, viewed through changes in low-molecular-weight thiols such as glutathione, a major cellular antioxidant. Interestingly, some legumes also contain homoglutathione, a glutathione homologue in which the terminal amino acid, glycine, is replaced by beta-alanine. Research is currently being conducted on the occurrence and role of homoglutathione across the legume family in order to better understand the phylogenetic and / or chemotaxonomic significance of the different homologues. Moreover, research into DNA laddering (Kranner et al. 2011), volatile production and changes in gene expression during ageing has been conducted using seeds of Pisum sativum, and infrared thermography has been used to diagnose seed quality non-invasively (Kranner et al. 2010).
Seeds of some legumes are intolerant of drying, including Parkia speciosa from Asia, requiring the development of an innovative conservation strategy. Using differential scanning calorimetry to reveal the physical changes in water during cooling it has been possible to successfully cryopreserve shoot-tips of this food species (Nadarajan et al. 2008).
The outputs of the project are being published in peer-reviewed journals. Four PhD students and several college-based sandwich course students and work experience students have been trained in the framework of this project and have contributed to the publication output. The paper on 200-year old seeds (Daws et al. 2007) has received much interest from national and international newspapers and radio, and also featured in the BBC’s ‘A Year at Kew’. The press release regarding non-invasive techniques (Kranner et al. 2010) has also stimulated interest internationally, especially within the seed trade. Within RBG Kew this project has close links with several other projects being coordinated through other science teams such as the “Millennium Seed Bank Partnership”.
- Colville, L., Bradley, E.L., Lloyd, A.S., Pritchard, H.W., Castle, L., Kranner, I. (2012) Volatile fingerprints of seeds of four species indicate the involvement of alcoholic fermentation, lipid peroxidation, and Maillard reactions in seed deterioration during ageing and desiccation stress. Journal of Experimental Botany 63: 6519-6530.
- Birtić, S., Colville, L., Pritchard, H.W., Pearce, S.R. & Kranner, I. (2011) Mathematically combined half-cell reduction potentials of low-molecular-weight thiols as markers of seed ageing. Free Radical Research 45: 1093-1102.
- Kranner, I., Chen, H., Pritchard, H.W., Pearce, S.R. & Birtić, S. (2011). Seed ageing correlates with inter-nucleosomal DNA fragmentation and loss of RNA integrity. Plant Growth Regulation 63: 63-72.
- Kranner, I., Kastberger, G., Hartbauer, M. & Pritchard, H.W. (2010). Non-invasive diagnosis of seed viability using infrared thermography. PNAS 107: 3912-3917.
- Nadarajan, J., Mansor, M., Krishnapillay, B., Staines, H.J., Benson, E.E. & Harding, K. (2008). Applications of differential scanning calorimetry in developing cryopreservation strategies for Parkia speciosa, a tropical tree producing recalcitrant seeds. CryoLetters 29: 95-110.
- Daws, M.I., Davies, J., Vaes, E., van Gelder, R. & Pritchard, H.W. (2007). Two-hundred-year seed survival of Leucospermum and two other woody species from the Cape Floristic region, South Africa. Seed Science Research 17: 73-79.
Project Partners and Collaborators
University of Buenos Aires
University of Graz
Germplasm Bank of Wild Species, Chinese Academy of Sciences, Kunming
Graduate University of the Chinese Academy of Sciences, Beijing
University Paris Est
University Pierre et Marie Curie
University of Bielefeld
University of Freiburg
Forest Research Institute of Malaysia (FRIM), Kuala Lumpur
NRC Handelsblad, Herengracht, Amsterdam
Russian Academy of Sciences, Kazan
University of KwaZulu-Natal, Pietermaritzburg
University of Salamanca
Food and Environment Research Agency, York
University College London
University of Abertay, Dundee, Scotland
University of Sussex, Brighton
DEFRA grant ZZ0105
Leverhulme Trust grant F/00 731/C
Millennium Commission, Wellcome Trust, Orange PLC for the MSBP
Many individuals, other charitable trusts and businesses have donated significant sums towards the collecting programme.