Our Blog: Plants and other Stories
Above: Lebeckia. Photo by Marianne le Roux.
Have you ever considered the origin of the beans and peas we consume when you are preparing tasty curries, soups and salads? They form part of many cooking traditions and people living in rural areas rely heavily on beans as a staple food. Beans and peas also serve as a substitute to animal protein particularly in vegetarian diets.
The legume family (beans and peas) is the most important after the grass family economically, as it is used in agriculture, construction, ecotourism, furniture, horticulture, manufacturing processes, mining, paper, pest control and textile industries.
It serves as a major food source for humans and forage source for animals. It is also used to improve soil fertility as green manure or in crop rotation. Many legumes have the ability to capture atmospheric nitrogen through a symbiotic interaction with soil bacteria. This quality allows legumes to establish in nutrient-poor soils as pioneers which could help to stabilise soils and provide other plants with favourable growing conditions, ultimately curbing erosion and providing an ecosystem service.
The humble bean
Beans and peas are the seeds carried inside the fruits called pods or legumes. The pod is made up of a single carpel (female fruiting body) that usually bursts open along both sutures when it becomes dry, exposing the seeds to the environment. Beans and peas are often, although not always, kidney-shaped.
They consist of the outer coat or testa that protects the inner embryonic leaves or cotyledons that contain the nutritious part of the seed. When the seed germinates, nutrients from the cotyledons are used to support growth of the seedling. And it’s these cotyledons that are so important in our diets. Legume seeds usually have high levels of nitrogen in the form of amino acids and proteins due to their nitrogen fixing ability.
Dhal and delicious
Both beans and peas, except split peas and split lentils known as dhal, have to be soaked before they are cooked. The soaking leaches out indigestible sugars and the cooking (at least 15 minutes) makes those anti-nutritional enzymes that cannot be digested by the human metabolism inactive.
Some of the most common legumes that form part of the human diet include carob, chickpeas, lentils, lupins, peanuts or groundnuts, garden peas and soybeans. Knowing the identity of the beans and peas we are consuming is important and relies on the process of naming and classifying (taxonomy).
Above: The home page of the Legume Data Portal, www.legumedata.org.
Has it ‘bean’ labelled correctly?
Legumes are widely distributed across the entire globe and depending on their origin and country where they are cultivated, a single species may have several common names, or one common name that may refer to many species. This is problematic when you need to refer to a specific species. After all, which name do you choose to use knowing that everyone is also thinking of that exact same species?
There’s a solution for this: an international group of 80 legume taxonomic experts from 24 countries collaborated to create an up-to-date consensus species list under the umbrella of the Legume Phylogeny Working Group. This initiative is led by researchers at the South African National Biodiversity Institute (SANBI), Université de Montréal, Global Biodiversity Information Facility (GBIF) and the Royal Botanic Gardens, Kew. This definitive list is important as it allows researchers to communicate more effectively about legume species including research related to legumes within the areas of conservation, agriculture, food security, forestry and climate change.
This new legume checklist has been examined by global legume experts, making it the most accurate and current list available for researchers. This should help to speed up the pace of species identification – at a time of unprecedented biodiversity loss.
Above: Some variation of flowers in the bean and pea family. A. Lessertia, B. Lebeckia, C. Afzelia, D. Elephantorrhiza, E. Tylosema. A, B, D and E photographed by Marianne le Roux, C photographed by Graeme White (iNaturalist).
There’s a final hiccup
Scientific names help to avoid confusion between species. Taxonomists have a set of rules (the International Code of Nomenclature for algae, fungi, and plants, or in short ICN) they follow when naming species. Every species should have only one accepted scientific name. However, scientific naming is also occasionally challenging as some of these species are widely distributed and people have named them not knowing that a name may already exist prior to the information technology era.
More commonly, as we learn more about these species through research, species are transferred from one genus to another in an attempt to create a more natural and stable classification. As a result, one entity can have two names, an accepted name and a synonym. In some scenarios, people have chosen to follow one classification over another, creating alternative or parallel classifications. The legume expert community is attempting to solve duplication and alternative classifications to provide a single, community-endorsed classification system that can serve as the primary name source for all future research and information sharing through online platforms.
Above: Fruit variation Above: Fruit variation in shape and size (A-M) found in the bean and pea family, showing how the pods split open along two sutures when dry (A, F), and what the seeds look like inside the pods (B, G). A, E, I, J, M photographed by Marinda Koekemoer, B photographed by Pieter Bester, C, D, F, H, K, L photographed by Marianne le Roux, and G photographed by Troos van der Merwe (iNaturalist). A. Afrocalliandra, B. Vachellia, C. Rafnia, D. Aspalathus, E. Pterocarpus, F. Argyrolobium, G. Afzelia, H. Lupinus, I. Zornia, J. Adenolobus, K. Crotalaria, L. Lessertia, M. Entada.
Underrated yet in high variety
Right now, this scientifically verified list recognises 22 360 species in 772 genera. The legume component of The World Checklist of Vascular Plants was used as the starting list and in total, 2 011 names were added and 6 167 corrections were made. The published list is entitled The World Checklist of Vascular Plants: Fabaceae, vers. June 2021.
The checking of names will continue as the entire list has not yet been verified. A major contribution on the subfamily Caesalpinioideae is currently being prepared in two special volumes of Advances in Legume Systematics that will be published during 2022 in the peer-revied journal Phytotaxa. These publications will contain several name updates and will, after its publication, be incorporated into the legume checklist.
Above: The search function to browse or search the up-to-date legume checklist on the Legume Data Portal at www.legumedata.org.
Bean around the world
Coupled with the checklist, a Legume Data Portal (www.legumedata.org) has been launched with the support of the GBIF. This portal allows users to access all sorts of legume-related data, including the up-to-date checklist, distribution data, information about the research of the working groups, the legume community’s annual magazine The Bean Bag and news items. The new checklist will now be kept up-to-date and will also be used – freely – in significant global biodiversity online platforms. This should greatly improve and simplify communication about legumes.
Legume Data Portal, 2021, viewed 1 December 2021.
Legume Phylogeny Working Group (LPWG), Andrella, G.C., Atahuachi Burgos, M., Bagnatori Sartori, A.L., Balan, A., Bandyopadhyay, S., Barrett, R.L., Barbosa Pinto, R., Brullo, S., Boatwright, J.S., Broich, S.L., Bruneau, A., Cardinal-McTeague, W., Cardoso, D., Castro Silva, I.C., Cervantes, A., Choo, L.M., Cobra e Monteiro, T., Compton, J., Crameri, S., de la Estrella, M., Delgado-Salinas, A., Dorado, O., Duan, L., Egan, A.N., Fritsch, P., Falcão, M., Farruggia, F., Fortuna-Perez, A.P., Giusso del Galdo, G.P., Goncharov, M., Gregório, B.S., Javadi, F., Klitgaard, B.B., Kramina, T., Lachenaud, O., Lana C. Atunes, L., Le Roux, M.M., Ledis Linares, J., Lewis, G., Li, S.-J., De Lima, H.C., Mansano, V., Mashego, K.S., Mattapha, S., Montenegro Valls, J.F., Moteetee, A., Murphy, B., Ohashi, H., Ohashi, K., Pandey, A., Pennington, R.T., Ramos, G., Phillipson, P., Povydysh, M., Rakotonirina, N., Ranzato Filardi, F., Sanjappa, M, Santos-Guerra, A., Seijo, G., Schley, R., Schrire, B., Schütz Rodrigues, R., Seleme, E.P., Şentürk, O., Silva de Carvalho, C., Silva Flores, A., Simpson, C.E., Sirichamorn, Y., Soares Gissi, D., Sokoloff, D., Stirton, C.H., Subramaniam, S., Thulin, M., Torke, B.M., Van der Burgt, X., Vatanparast, M., Wilding, N., Wojciechowski, M., Yi, T., Zhang, R., 2021, The World Checklist of Vascular Plants (WCVP): Fabaceae, vers. June 2021, R. Govaerts (ed.), viewed 1 December 2021.
Lewis, G., Schrire, B., Mackinder, B., Lock, M. (eds.), 2005, Legumes of the World, Kew: Royal Botanic Gardens.
Turland, N.J., Wiersema, J.H., Barrie, F.R., Greuter, W., Hawksworth, D.L., Herendeen, P.S., Knapp, S., Kusber, W.-H., Li, D.-Z., Marhold, K., May, T.W., McNeill, J., Monro, A.M., Prado, J., Price, M.J., Smith, G.F. (eds.), 2018, International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Regnum Vegetabile 159, Glashütten: Koeltz Botanical Books.
Van Wyk, B.-E., 2005, Food plants of the World, Pretoria: Briza publications.
BotSoc Council member Prof Charles Stirton unpacks the wonders of Cape Legumes.
Know, grow, protect and enjoy South Africa’s indigenous plants.
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