Climate Change, Species Vulnerability and Germination Thresholds
The temperature and salinity limits to germination can be modelled and used as predictive tools to assess the impact of climate change on seed germination.
A seed of the halophyte Suaeda maritima, one of the model species used to study seed responses to salt stress
Climate change, including temperature, and expansion of agriculture into marginal areas (such as salt affected lands) has resulted in many species growing in sub-optimal environments and being exposed to abiotic stress factors. Species vulnerability to stress factors is not only a function of length and duration of exposure (Kranner et al., 2010) but is also determined by phenotypic plasticity (i.e. sensitivity to stress) and genotype (i.e. adaptability to stress). Previous MSBP research (projects ‘Seed Responses to Climate Change and Environmental Extremes’, ‘Maternal Environment Effects on Seed Germination and Dormancy: Inter-Site and -Season Comparisons’, Separating Cardinal Temperatures for Seed Dormancy and Germination in Temperate, Sub-Tropical and Tropical Species) has studied the phenotypic plasticity present in seed germination and dormancy in response to climate change and maternal environment in a range of species. However, germination threshold models, which can be used as predictive tools, have not yet been considered.
Germination occurs between a base and a ceiling threshold temperature, with the highest germination rate occurring at an optimal temperature. The base temperature of germination can be incorporated into the calculation of thermal time for germination (i.e. temperature accumulation above the base temperature for the completion of germination) which is a measure of species sensitivity to temperature change. Such threshold models are currently being developed for over 50 taxa of Cactaceae through the research network established by the ‘Cactus Seed Biology Database’ project. We are examining the extent of phenotypic plasticity in cactus seed germination to give a perspective on changing environmental temperature and natural plant regeneration. Studies have been extended to threatened species of Sardinia, exploring threshold temperatures for morpho-physiological dormancy release and germination (Mattana et al., 2011).
Phenotypic plasticity is also being examined in species during germination in saline environments. Traditional crop species are not adapted to these stressful environments. However, halophytes have evolved to live in saline environments and offer untapped sources of oilseeds, forage and biomass. Currently, salinity threshold models are being developed in a range of halophytic species including from Northwest China and research has commenced into the mechanisms by which halophytic seeds tolerate salt stress during germination. The University of Sussex has also contributed their eHALOPH database of over 1500 species to the Seed Information Database. Our research on halophytes preceeded a four year EU COST Action FA0901 (putting halophytes to work – from genes to ecosystems, 2009-2013). Participation in the Action provides an excellent opportunity to bring together extensive seed collections of halophytic genera, such as Salicornia, developed by researchers across the EU and associated countries. In collaboration, we will progress our research into species vulnerability beyond phenotypic plasticity and consider the genotype in species adaptability to saline environments.
To date, the outputs of this project, which is part of the ‘Sleeping Beauties’ research theme, include the ‘Cactus Seed Biology Database’ which details the germination of 300 taxa (of which 86 records are new data), peer-reviewed scientific papers, and data have been presented at several conferences including plenary and keynote lectures. Furthermore, a visiting professor from Tarim University, China, and seven more visitors and students have contributed to this project; two UK college-based sandwich course students have also completed projects on ‘seeds and salt’.
Project partners and collaborators
Universidad Nacional de Salta
Banco Base de Germoplasma, CIRN-CNIA- INTA, Buenos Aires
University of Sofia
Instituto de Investigaciones Agropecuarias
Jardin Botanico Nacional ¨Dr Rafael Maria Moscoso¨, Santo Domingo
University of Provence
Università degli Studi di Cagliari
Instituto Potosino de Investigación Científica y Tecnológica, San Luis Potosí
Universidad Autónoma de San Luis Potosí
Universidad Nacional Autónoma de México
Universidad Nacional Agraria La Molina, Lima
University of Sussex
MSBP Enhancement grant, MSBP, Defra
Key papers published since 2006:
Mattana, E., Pritchard, H.W., Porceddu, M., Stuppy, W.H. & Bacchetta, G. (2011). Interchangeable effects of gibberellic acid and temperature on embryo growth, seed germination and epicotyl emergence in Ribes mulitflorum ssp. sandalioticum (Grossulariaceae). Plant Biology doi: 10.1111/j.1438-8677.2011.00476.x (IF 2.409).
Flores, J., Jurado, E., Chapa-Vargas, L., Ceroni Stuva, A., Dávila Aranda, P., Galíndez, G., Gurvich, D., León-Lobos, P., Ordoñez, C., Ortega-Baes, P., Ramírez Bullón, N., Sandoval, A., Seal, C.E., Ulian, T. & Pritchard H.W. (2011). Seeds photoblastism and its relationship with some plant traits in 136 cacti taxa. Environmental and Experimental Botany 71: 79-88 (IF 2.699).
Kranner, I., Minibayeva, F.V., Beckett, R.P., & Seal, C.E. (2010) What is stress? Concepts, definitions and applications in seed science. New Phytologist 188: 655-673 (IF 6.516; times cited = 10).
Seal, C.E., Zammit, R., Scott, P., Flowers, T.J. & Kranner, I. (2010) Glutathione half-cell reduction potential and alpha-tocopherol as viability markers during the prolonged storage of Suaeda maritima seeds. Seed Science Research 20: 47-53 (IF 1.250).
Daws, M.I., Kabadajic, A., Manger, K. & Kranner, I. (2007) Extreme thermo-tolerance in seeds of desert succulents is related to maximum annual temperature. South African Journal of Botany 73: 262-265 (IF 1.106).
Conferences and workshop:
Kranner I and Seal CE. ‘Global Forum on Salinization and Climate Change‘, Valencia, Spain, 27-28 October (2010): What is stress? Concepts, definitions and implications for plant growth in saline environments. [Key note lecture]
Pritchard H.W., Li Z-J et al. Characterising seed biodiversity for functional performance under saline conditions. 5th European Plant Science Organisation Meeting, Finland, 2010.
Kranner I and Pritchard HW. ‘Tree seeds in a changing climate: stress concepts and case studies’, Tree Seeds 2008 – Trees, Seeds and a Changing climate, Brighton, United Kingdom 22-25 Sep 2008 [plenary lecture]
Mattana E., Pritchard H.W., Porceddu M., Stuppy W.H., & Bacchetta G. Interchangeable effects of gibberellic acid and temperature on embryo growth, seed germination and epicotyl emergence in Ribes mulitflorum ssp. sandalioticum (Grossulariaceae). Seed Ecology III, Utah 2010.
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