Millennium Seed Bank blog
Welcome to the Millennium Seed Bank blog. There is a lot going on behind the scenes at Kew's Millennium Seed Bank (MSB) - not only here at Wakehurst but also with our partners all over the globe. We will be blogging about our seed collecting trips, local events, research projects and discoveries as well as everyday goings on.
We currently have seeds from more than 30,000 species of wild plants in long term storage and continue to receive seed collections from all over the world. It is an amazing place to work and we hope to share our passion for seed conservation with you via our blogs.
Between 27 August and 5 September I was involved in a seed collecting trip on the Spanish side of the Pyrenees. We went with the team from the Botany Department of the Sociedad de Ciencias Aranzadi (San Sebastián) who manage the Basque Country Seed Bank. The team was formed of two botanists and two biology students. During the last two days, we were joined by three botanists from the Jardín Botánico Atlántico (Gijón) and the Jardín Botánico de Olarizu (Vitoria).
LaKartxela mountain in the West Pyrenees (Photo: Teresa Gil)
The Pyrenees contain one of the highest levels of plant diversity in Europe (4,000-4,500 species). This is due to the complexity of the mountain range which has a high altitudinal gradient and a diverse range of climates, geology and ecosystems. Around 200 plant taxa are endemic to the Pyrenees.
Climbing to Alanos collecting area (Photo: J. Garmendia)
Aim of the trip
The aim of this field trip was to collect seeds of target endemic species and structural species of habitats of community interest, as well as to collect population data that would help with monitoring their conservation status.
We collected 83 taxa, most of them endemic to the Pyrenees and to the Pyrenees-Cantabrian region. Forty of the taxa are new collections for the Millennium Seed Bank. The seeds were collected following the ENSCONET protocol and associated data, herbarium vouchers and photos were gathered for each seed collection. The preliminary field work done to locate the plant populations and to check the phenological status of the populations was key to maximising the seed collecting.
I have been always fascinated by the plant diversity and endemicity of the Pyrenees. Collecting the seeds of so many different plants was a very enriching and interesting experience. I had the opportunity to observe, learn, understand and share with other botanists the diversity of reproductive and seed dispersion strategies that high mountain plants have.
Collecting seeds of Phleum alpinum in Lakora using a transect methodology (Photo: J. Garmendia)
Some of the target species populations are located at high altitude and several hours of trekking were required to reach them. Once arrived, we were a very efficient group of seed collectors. For each taxa we decided beforehand to adopt the most effective seed collecting strategy.
Collecting seeds of Callitriche palustris in Lakora lake (Photo: Teresa Gil)
In the first week we collected in the Navarra region. We spent four days collecting in the Pikatua, Lakora, LaKartxela and Ori mountains.
Collecting seeds of Festuca skia on Lakora mountain (Photo: J.Garmendia)
Fog in the mountains
The first four days we were working in a thick fog which, unfortunately, obscured the beautiful views of the landscape.
Collecting seeds in the fog on Ori mountain (Photo: Teresa Gil)
It was much cooler than we expected; however, with warm jackets and high spirits, we managed to make some good collections.
Collecting seeds in the fog on Ori mountain (Photo: Teresa Gil)
For example, we made good collections of several endemic plants such as Teucrium pyrenaica, Onobrychis pyrenaica and Petrocoptis hispanica.
Flowers of Teucrium pyrenaica (Photo: Teresa Gil)
Fruits of Teucrium pyrenaica (Photo: Teresa Gil)
Fruits of Onobrychis pyrenaica (Photo: J.Garmendia)
Collecting Petrocoptis hispanica requires a lot of patience and concentration. It was almost a meditation experience, as we collected the capsules one by one from small plants growing in the cracks of the rocks.
Rocky habitat of Petrocoptis hispanica (Photo: Teresa Gil)
Most of them were empty so we needed to select those with at least one seed or, if we were lucky, with more than two tiny, black seeds.
Petrocoptis hispanica (Photo: Teresa Gil)
Capsules of Petrocoptis hispanica showing one black seed (Photo: Teresa Gil)
We also tried to collect the endemic Viola cornuta, but we could not find enough fruits. It seems this plant disperses its seeds very quickly. After looking carefully in the area where the population was, we gave up and decided to leave it for next year as we only found one beautiful capsule ready to be collected.
Capsule with seeds of Viola cornuta (Photo: Teresa Gil)
Collecting in the Petraficha mountain pass
During the second week we were collecting in the Aragon region in the Petraficha mountain pass and in different parts of Alanos peaks. Fortunately, it was sunny and warm, so seed collecting was thankfully much easier. We collected seeds of several endemic taxa like Galium cespitosum, Galium pyrenaicum and Lilium pyrenaicum. Collecting Galium cespitosum took some time but we were a very good group of seed collectors and within one hour we made a good collection and were ready to keep walking and collecting.
Collecting seeds of Galium cespitosum in Petraficha mountain pass (Photo: Teresa Gil)
Detail of plant and fruits of Galium cespitosum (Photo: Teresa Gil)
Lunch with vultures
Almost every day we were visited by a pair of Bearded Vultures (Gypaetus barbatus) during our lunch break. They were probably flying over our heads the whole time but we were so focused on seed collecting that we did not realise they were there until we sat down on a rock and began looking at the landscape while we ate our yummy sandwiches.
Processing and planning
Every evening when we came back to the hostel we spent some time processing the herbarium vouchers and taking care of the seed collections (post-harvest handling). Due to the fog of the first few days the seeds were completely soaked and there was a high risk of deterioration through ageing or mould. Drying them was an urgent task.
Seeds drying (Photo: Teresa Gil)
Halfway through our trip we had a meeting at the Instituto Pirenaico de Ecología (CSIC) in Jaca, who warmly hosted us. We discussed a project proposal to develop an “Ex-situ conservation programme in the North of Spain” including the Cantabrian range and the Pyrenees. It was a very fruitful meeting and once we successfully raise enough funds we will start its implementation, hopefully in time for the next seed collecting season.
Herbarium vouchers processing (Photo: Teresa Gil)
Now staff members from Sociedad de Ciencias Aranzadi are busy cleaning the collected seeds and we are looking forward to receiving the duplicates at the Millennium Seed Bank in the coming months.
- Teresa -
- European Native Seed Conservation Network (ENSCONET)
- Aranzadi Science Society
- Jardín Botánico Atlántico
- The Seed Bank Olarizu Botanical Garden
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I suspected a title mentioning gladiators and beer would pique your interest! Now before you slip into a reverie about Russell Crowe, encased in armour and fighting off a dozen gladiators, let me bring you back to earth (I promise it’ll be worth it) to tell you about the incredible barley.
Barley growing in Pembrokeshire in Wales (Photo: Wolfgang Stuppy)
Hordeum vulgare, as it is known in Latin, is the fourth most important cereal crop in the world after wheat, maize, and rice. It is mainly grown to feed livestock but second to this is its importance in malting for beer brewing and whiskey making. Those savvy Ancient Egyptians caught on to the idea early and archaeological evidence of barley grains found in the great pyramids of Egypt 5,000 years ago, as well as in ancient Egyptian and Sumerian writings, suggest that our ancestors have been enjoying the good stuff for millennia.
Some 4,000 year-old barley grains from the Middle Kingdom site of Kahun, Egypt. Excavated in 1889 and now housed at the Economic Botany Collection (Photo: Mark Nesbitt)
The cultivation of barley occurred in the Fertile Crescent, the region surrounding modern day Israel and Jordan, around 8,000 BC. Its wild ancestor is Hordeum vulgare subsp. spontaneum and while the two grasses are very closely related, the main difference between them is found in the spikes that hold the seeds. In wild barley they are brittle, which means that once the seed matures the spikelets separate easily enabling seed dispersal, whereas cultivated barley has non-shattering spikes which means that the plant holds onto the mature seeds, making them much easier to harvest. (This distinction between wild and cultivated forms is mirrored in many other crops.)
The development of non-shattering spikes
This is how it all came about. Domestication begins with the harvesting of seeds from a wild population of plants. Some plants will have lost the natural ability to shed their seeds when ripe and these were more likely to be collected and re-sown than those plants whose seeds were already scattered. My seed collecting friends have confirmed this – it is far easier to pull the seeds off a plant than to scrounge around on the ground for the matured fallen seed which, supposing it even belonged to the plant you’re interested in, could already be mouldy or pest-ridden. So, generations later, this non-shattering characteristic would become fixed in the population, and today one of the most striking features of nearly all crop plants is that, unlike their wild relatives, they retain their seeds and depend almost entirely on humans to gather and sow their seeds. Indeed, many crops would die out if there were no humans to sow or plant them.
Barley is a tough cookie and makes for a tough gladiator too
From arctic latitudes and alpine altitudes to salty desert oases, barley can grow in extreme environments where other crops are unable to survive. It is typically a temperate crop but it can also be found growing in tropical countries where poor farmers are able to benefit from barley’s resilience to hostile, dry, environments. In places like Nepal, Tibet and Ethiopia farmers grow barley on mountain slopes at higher elevations than other cereals and in the dry areas of the Middle East and North Africa, barley is often the only suitable crop. The key producers of barley today are Russia, Canada, Germany, France, Ukraine, Spain, Turkey, UK, Australia, USA and Denmark.
Tibetan barley fields (Photo: Richard W. Hughes)
As well as being a fodder and malting crop, barley is also cultivated for direct human consumption. Its value as a high energy carbohydrate source has been documented since Roman times when gladiators were called hordearii, literally meaning “barley men”. Gladiators would fatten up on a diet of simple carbohydrates such as barley so that when they entered the ring in a battle to the death, the extra layers of subcutaneous fat would protect them from cut wounds and shield nerves and blood vessels. Apparently fat gladiators made for a more spectacular show. Gladiators wounded only at the fatty layer would be able to keep on fighting and bloody, maimed, unrelenting chubby gladiators were exactly the kind of thing Romans went wild over. In addition to being a gladiator-worthy carbohydrate source, certain barleys are also remarkably high in protein, such as some Ethiopian varieties which contain up to 18% protein.
A spiritual experience (and this time I’m not talking about whiskey!)
Today, barley is eaten in several remote parts of the world such as Tibet and parts of North Africa where nothing else can grow. Tsampa, a delicious Tibetan dish made with roasted barley and prepared with tea, is consumed daily in villages throughout Tibet.
Tibetans enjoying tsampa (Photo: Roland von Bothmer)
For Tibetans, the preparation and consumption of tsampa is a sacred and ritualised process where the ingredients barley flour, butter, tea and cheese represent the four elements of the earth – namely earth, fire, water, and wind. When making tsampa, the mixture of these ingredients must form a pile that reaches higher than the mouth of the bowl. This pile symbolises the universal mountain of Tibetan Buddhism, which is a representation of the entire world. Before the meal, Tibetans chant and make offerings to all sentient beings by throwing small bits of tsampa into the air or on the ground. In Tibetan culture, barley flour is also used to make incense offerings to the mountain gods and often forms a part of religious offerings in temples.
Barley improvement through the use of Crop Wild Relatives
Like all crops, barley has to contend with pests, diseases and environmental stresses such as drought, salinity and climate change. Changes in drought and salinity levels, which are expected to worsen with climate change, will not just affect beer production but will also impact on the food supply of those people who depend directly on barley as a staple part of their diet. Lowering greenhouse gas emissions is a necessary step towards stalling the effects of climate change but, in addition to this, we need to arm ourselves against climate change by adapting our crops to future climate scenarios. The wild relatives of barley are a rich source of genetic diversity which has great potential for barley improvement. Drought- and salt-tolerant genes have been identified in the crop wild relative Hordeum vulgare subsp. spontaneum and disease resistance has been found in Hordeum bulbosum. Other traits from H. bulbosum, such as perenniality, have the potential to alter the crop for a more sustainable production and maintenance of genetic diversity.
Barley Varieties Displayed at The International Center for Agricultural Research in the Dry Areas (ICARDA) (Photo: Global Crop Diversity Trust)
The Adapting Agriculture to Climate Change project, jointly organised by the Millennium Seed Bank and the Global Crop Diversity Trust, aims to protect, collect and prepare the wild relatives of 29 key food crops, including barley. By making these seeds available to pre-breeders the useful traits they hold can be used to improve crops and therefore safeguard our future food security.
And finally, something for our furry friends
Those of you with pet cats will have noted their occasional craving for grass. Rather than have them nibbling on your houseplants, Cat grass (Hordeum vulgare subsp. variegata) is a variety of barley which has been cultivated to satisfy the highly sophisticated tastebuds of our feline companions. It makes quite an attractive houseplant too!
A cat licking her chops over cat grass (Photo : Jungleseeds)
- Sarah -
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Thank goodness it’s Friday! How many of us have said that during our working lives? I know I have. In fact, I still do, but now I say it not because the weekend is near, but because Friday is my Seed Bank volunteering day.
What do Seed Bank volunteers do? Well, some assist in the research and management support sections, but most of us work in the conservation and technology section. We help to clean the seeds which come in from all over the world, and prepare them for long-term storage. While awaiting cleaning, the seeds are stored at low temperature (15°C) and humidity (15% RH).
All sorts of techniques are used: simply sieving to remove debris can be enough in some cases, but other seeds may need to be crushed to remove the pod (think peas), or rubbed to remove the husk (think grasses) or the pappus (think dandelions). Sieving is fine if the seeds and the debris are of different sizes, but not much use if everything is the same size. So long as the seeds and the debris are of different weights we can use a device called an aspirator – a sort of mechanised winnowing machine. The seeds are dropped down through an upward current of air and the lighter material is blown upwards to land in one box and the heavier material drops down to land in a separate box.
Sometimes it is just not possible to remove all the debris but we try to reduce the bulk as much as possible as space in the Seed Bank vault is at a premium.
Over the last few weeks we have been working on collections from the Falkland Islands, many of them grasses, and I think we’ll be glad when they are finished, as getting the seeds off the stalks and out of their husks has been very time-consuming.
Me wrestling with Falkland Islands grass seeds (Photo: Jean Helliwell)
We all enjoy our volunteering at the Seed Bank and are happy to turn our hands to any task, but please no more grasses for a bit!
There are currently 15 volunteers working in the Millennium Seed Bank. Each volunteer commits to at least one full day per week which is a great help. Due to the high profile of the MSB there is already a large waiting list of individuals wishing to donate their time for this great project so currently we are at full capacity.
- Jean Helliwell -
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What goes on at a Seed Festival?
Seed swaps encourage and inspire people to grow vegetables and fruit and to experiment with different varieties, particularly heritage and traditional types that were once so important in British gardens.
Swap them, buy them, learn about growing them…it’s the festival that’s all about SEEDS! (image: Nicky Toothill)
Gardeners will be able to swap seeds from plants they have grown at home for seeds from a range of garden vegetables and flowers grown by other enthusiasts. Kew’s Millennium Seed Bank at Wakehurst has the largest wild seed collection in the world - although we won’t be using seeds from the Seed Bank in the Seed Swap!
No Seeds To Swap?
You don’t have to bring seeds with you to swap. Seeds from allotment and community groups and specialist growers will be available for a small donation.
In need of ‘seedy’ advice?
We have some great informative talks and practical demonstrations lined up this year to help give you advice on saving and storing your seeds. There will also be a wealth of expert advice and information on hand to help you make the most of your own plot, whether you have a large garden, a small backyard, or even just a window box.
Stall holders hold a wealth of advice....and smiles! (Image: Nicky Toothill)
Inspiring and Informative Talks
There will also be a range of other great talks from some amazing people that are not to be missed. So far the following speakers have been confirmed:
Tom Hart-Dyke - author of 'Plant Hunter with Passion', 'Kidnapped in Paradise’
Tom is a horticulturalist, plant hunter and author. Famously taken captive in 2000 in the Columbian jungle while plant hunting with a companion, he kept himself going by designing his dream garden. On returning to Lullingstone Castle in Kent he decided to make his dream a reality, designing and building The World Garden within the walled Victorian herb garden (the subject of a BBC2 series). Tom’s adventures continue as he travels the world hunting for plants. (Tom's website)
Olly Whaley – Food Security
Olly is Kew’s Latin America Projects Officer. After starting work in the Amazon rainforest 20 years ago, Oliver’s focus quickly shifted to the arid regions and conservation of tropical dry forest - key regions for the production of food. Today he leads a programme in Peru, enabling local people to benefit from native threatened crops and develop sustainable agriculture in a globalised world, whilst at the same time conserving and restoring the supporting ecosystem.
Neil Munro - 'Going to Seed: Top Tips for Saving Seeds from Vegetables'
Neil is Manager of the Heritage Seed Library (HSL) at Garden Organic. HSL maintains a seed collection, mainly of European varieties that have either been dropped from popular seed catalogues, or are landraces or heirloom varieties that have never been available through catalogues. The seed collection is made available to HSL members. Neil will tell us how we can grow seeds from heritage vegetables and how to ensure each variety remains pure.
James Wong signing his book for fans following his talk ‘Homegrown Revoloution’ at last year’s Seed Swap (Image: Nicky Toothill)
Behind the Scenes Tours
For those of you who have an inquisitive mind or just fancy having a snoop behind the scenes at Wakehurst Place, this year we will be running the following tours at regular intervals throughout the day - but places are limited, so sign up when you arrive to avoid disappointment!
- Nursery Tours - for more information download the Programme of Events (pdf)
- Tours of Kew’s Millennium Seed Bank’s Vault - for more information download the Programme of Events (pdf)
The range of activites for this year’s Seed Festival will keep kids of all ages entertained, although we can’t promise they won’t get messy!
Getting creative (and messy!) on one of the many children’s activities tables last year (Image: Nicky Toothill)
Shopping & Food Stalls
Last year’s event packed in over 50 stall holders ranging from seed suppliers, food stalls, experienced growers and local producers and this year will be no different! Here are just some of this year’s confirmed stall holders:
- Thomas Etty Esq
- Beans and Herbs
- Organic Gardening Catalogue
- Infinity Foods Cooperative Ltd
- Jaju Beans and Leaves
- Tulleys Farm
- Seedy Sunday
- Sussex Community Seed Bank
- Garden Organic - Heritage Seed Library
- Transition Horsham
- Jam Today Jam Tomorrow
- National Society of Allotment and Leisure Gardens
There will also be various food and beverage stalls to feed your appetites from hot snacks to homemade cakes and coffee to cater for all your hungry desires and thirst cravings!
No seed festival would be complete without some seed-related entertainment and we have some unusual diversions for you to listen to, watch, and even participate in!
- Cooking Demonstrations with tasty samplers - for more information download the Programme of Events (pdf)
- Association of Pole-Lathe Turners - Sussex Local Group
Visitors will also be able to find out about the vital work of Kew’s Millennium Seed Bank and discover how Kew is helping to safeguard the world’s most endangered plants.
- Gemma Toothill -
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Why are some fruits poisonous?
In a comment on my last blog about the ‘dead man’s finger’, Tonio asked a very good question: "Why are some fruits poisonous?" After all, colourful, fleshy, juicy fruits convey a message that’s universally understood, even by very small children: 'Eat me, I am a sweet treat!'
Sweet treats: a selection of harmless delicious fruits as we know and love them [Images from ‘The Bizarre and Incredible World of Plants’ by Wolfgang Stuppy, Rob Kesseler & Madeline Harley; Copyright Papadakis Publisher, Newbury, UK]
All too easily, the naivety of little children can trick them into mistaking shiny red, blue or black berries for sweet gifts from Mother Nature. Such a mistake can have fatal consequences if the berries of privet (Ligustrum vulgare, Oleaceae), deadly nightshade (Atropa belladonna, Solanaceae), white bryony (Bryonia dioica, Cucurbitaceae), daphne (Daphne mezereum, Thymelaeaceae) or mistletoes (Viscum album, Santalaceae) are involved. I have twin toddlers myself who put everything in their mouths that looks remotely edible, especially any bright and shiny fruit they find in the garden. More than once I observed with horror how they grabbed something from a plant and quickly popped it into their mouth. Fortunately, it was never anything dangerous and I could convince them to spit out whatever they just ‘sampled’ (this didn't apply to an earthworm that disappeared within a couple of seconds from in front of Ben while I was being distracted by his brother).
The colourful but very poisonous fruits of the European spindletree (Euonymus europaeus, Celastraceae) are very enticing to small children
Trouble in Paradise
After millions of years of evolution, the fleshy fruits of present-day plants should have had enough time to perfect their seductive skills and provide us with a cornucopia of super-delicious treats. After all, fleshy fruits want to be eaten so the pressures of natural selection should have driven them to become ever tastier and irresistible. So why, if the co-evolution between fruits and frugivores (= fruit-eating animals) has driven fruits to become increasingly attractive to animals, do so many wild fruits look delicious but taste so bad or are even poisonous? This seems an evolutionary paradox, if not an evil trick of Mother Nature. As with all misunderstandings, one needs to know the whole story. The truth is that Nature ain’t no paradise! More than anything else, fruits have to defend themselves against all kinds of predators. In this respect, little has changed since the olden days. From the very beginning, the potentially trouble-free relationship between fruits and genuinely beneficial dispersers has been spoiled.
The delicious looking fruits of the Virginia creeper (Parthenocissus quinquefolia, Vitaceae) contain oxalic acid which can cause severe poisoning and even death if a large number of the berries are ingested.
Flowers (top) and fruits (bottom) of white bryony (Bryonia dioica, Cucurbitaceae). Allegedly, about 15 berries can kill a small child
The fruits of Prunus spinosa (Rosaceae), better known as sloes, look delicious but have a very tart and astringent taste.
The good, the bad and the ugly
All kinds of animals, ranging from fruit flies to ourselves, learned to capitalize on the nutritious rewards provided by fruits without dispersing the seeds. These "pulp thieves" eat the flesh but do not swallow the seeds, either because their gape is too small (e.g. fruit flies, beetles) or because their intelligence and dexterity allow them to distinguish and remove indigestible parts of the fruit, like hard seeds (e.g. some parrots, monkeys and apes). By taking the reward without providing a transport service, pulp thieves have effectively become parasites in the previously mutualistic system.
Pulp thieves at work in Mexico: tiny fruit flies and a large longhorn beetle indulging into the sweet flesh of a prickly pear without helping to disperse the seeds
Take the best and leave the rest
Other thieves are less interested in sweet sugary pulp. Armies of insects, for example, have become specialised in preying on the most precious parts of the fruits, the seeds. What makes seeds such worthwhile targets is the highly nutritious food reserve which is meant to provide the small embryo plant they bear with energy during its germination.
A seed collection from Australia (Acacia penninervis). The bright spots inside the seeds in the x-ray image on the right show infestation with insect larvae
The worst culprits
Among the worst seed predators are beetles. True weevils (family Curculionidae), for obvious reasons also called snout beetles, form the largest group of beetles. Weevils can easily be recognized by their long snout, called a rostrum, at the end of which tiny chewing mouthparts are situated with which they bore their way in and out of plant tissue. The family includes more than forty thousand species and nearly all of them are plant predators feeding on leaves, shoots, roots, cambium, wood, flowers, fruits and seeds. For example, infestation of stored cereals, especially wheat, corn and barley, with the 3-4 mm long grain or granary weevil (Sitophilus granarius) can lead to the devastation of entire granaries.
An unknown snout beetle that was ‘caught in the act’ at the Millennium Seed Bank while munching on a seed collection from Madagascar
(Image from ’FRUIT – Edible, Inedible, Incredible’ by Wolfgang Stuppy & Rob Kesseler, Papadakis Publisher, Newbury)
More bad and ugly
However, granivorous (= seed-eating) insects are not the only animals preying on seeds. Birds and mammals also boast legions of granivores. Finches specialise on eating seeds and so do many rodents, including mice, rats, hamsters and squirrels. For many other animals, such as deer and pigs who feed on acorns if available, seeds form at least part of their diet. Apart from insects, birds and mammals with a hunger for seeds, Nature also harbours an endless diversity of much smaller predators prepared to devour any organic matter that is unable to defend itself: fungi and bacteria. With their resilient spores omnipresent in air, water and soil, these most dangerous of enemies can cause all kinds of diseases. A fruit riddled with fungal or microbial infection becomes unattractive to potential dispersers even if not completely destroyed. Either way, the result is failure of the fruit's vital mission to achieve the dispersal of its seeds.
Ugly pulp thieves: mould fungi can quickly make any fruit, like this peach, unpalatable to any bona fide dispersers
The evolutionary arms race
Literally, from ‘day one’, fruits had to find a trade-off between staying sufficiently attractive to bona fide dispersers whilst at the same time developing ways, such as poisons, to ward off predators. So on the one hand, fruits and bona fide dispersers co-adapted to each other to the benefit of both parties. On the other hand, the ancient game of attack and counter-attack between plants and predators sparked off another, sinister kind of co-evolution: an evolutionary arms race. Whilst selection pressures drove plants to constantly upgrade their mechanical and chemical defences, not only in their seeds and fruits but in all parts of their bodies, predators strove to overcome them through perpetual adaptation. For example, the seeds of legumes (Leguminosae) contain a gamut of toxic deterrents, ranging from cyanogenic glycosides, tannins and toxic amino acids to lectins (sugar-binding proteins), trypsin inhibitors (blocking protein digesting enzymes in the intestine) and bitter-tasting alkaloids, to name but a few. Small amounts of golden rain (Laburnum anagyroides), lupin (Lupinus spp.) or crab's eye (Abrus precatorius) seeds can cause deadly poisoning in animals and humans. Even pulses, although bred for centuries to suit human consumption, still require careful soaking, boiling, sprouting or fermenting before consumption to de-activate the toxins.
Even beans we buy from supermarket shelves need thorough boiling to render them harmless before consumption
Evolution is all about trade-offs
Alongside the chemical warfare against "larcenous elements", fruits still have to provide a worthwhile meal for bona fide dispersers. With so many parasites causing conflicting selective pressures, the traits of fleshy fruits are likely to be the result of a trade-off between becoming sufficiently repulsive to the "bad and ugly" whilst still remaining attractive to the "good". Therefore, the ecology of fruits and vertebrate frugivores can only be understood when taking into account the entire evolutionary triangle between fruiting plants, their mutualists and their predators and parasites, including granivores. Toxic chemicals in fruits and seeds most certainly evolved to mediate these interactions through balancing the potential cost of losing dispersers with the benefits of protecting seeds.
The crab’s eye (Abrus precatorius, Leguminosae) and the castor bean (Ricinus communis, Euphorbiaceae) contain some of the most poisonous substances found in nature (see my previous post on the illustrious castor bean).
Finally some good news!
The good news is that not only the parasites co-adapted with fruits and seeds, but also the mutualists. Whether or not a certain chemical compound is "poisonous" depends on the species in question. For example, many birds, the most important group of animal dispersers, are able to eat fruits that are toxic to humans and many other mammals.
The fruits of the appropriately called ‘dolls eyes’ (Actaea pachypoda, Ranunculaceae) from North America are poisonous to humans but harmless to birds, their main dispersers (Image from ‘FRUIT – Edible, Inedible, Incredible’ by Wolfgang Stuppy & Rob Kesseler; Copyright Papadakis Publisher, Newbury, UK)
Mistletoes and Deadly Nightshade
The berries of the European mistletoe (Viscum album, Santalaceae), a winter delicacy for small birds such as the mistle thrush (Turdus viscivorus, Turdidae), contain several small proteins that are highly toxic to mammals. The sweet-tasting black berries of the deadly nightshade (Atropa belladonna) hold a very potent mixture of tropane alkaloids (e.g. hyoscyamine, scopolamine and atropine) that interfere with acetylcholine receptors in the nervous system. Atropine in particular causes severe symptoms in humans, including sweating, vomiting, breathing difficulties, confusion, agitation, hallucinations and finally coma and death. Atropin also has a pupil-widening effect that was already known in ancient Greece, where an extract of 'belladonna' (Italian for 'beautiful woman') was frequently applied by women to enlarge their pupils. Widened pupils, naturally evoked by arousal, were supposed to 'intensify' eye-contact in romantic encounters.
The berries of the European mistletoe (Viscum album, Santalaceae) are highly toxic to humans but for small birds such as the mistle thrush they are a winter delicacy
Ever wished you could fly?
Deadly nightshade is also believed to have been among the main ingredients of the hallucinogenic brews of medieval Europe, including "flying ointments" that gave "witches" a sensation of flight. Apart from running the risk of getting you burnt at the stake, this kind of early drug abuse held other dangers. Atropa belladonna is one of the most poisonous plants in the Western Hemisphere and three berries are already enough to induce severe poisoning, not only in children but also in domesticated animals such as cats, dogs and livestock. However, wild birds and certain mammals, among them rabbits and deer, are able to eat the fruits and other parts of the plants without suffering any ill effects.
The fruit of the deadly nightshade (Atropa belladonna, Solanaceae)
So here’s the final answer:
The presence of poisons which are harmless for one group of animals whilst they are toxic to another enables plants not only to ward off predators but also to select the intended guild of dispersers from the available repertoire of frugivores.
(This blog is based on an excerpt from my book FRUIT– Edible, Inedible, Incredible by Wolfgang Stuppy & Rob Kesseler; Copyright Papadakis Publisher, Newbury, UK. All photos by me, Wolfgang Stuppy, unless otherwise stated.)
- Kew's online shop for copies of FRUIT- Edible, Inedible, Incredible
- The Wakehurst Seed Festival at The Millennium Seed Bank
- IncrEdible festival at Kew Gardens
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The Millennium Seed Bank Partnership works with over 80 countries worldwide as we work towards our current goal of collecting and storing seeds from 25% of the world's wild plant species. To complete such a target requires a wide range of skills and expertise including training, research, seed processing, database management and fundraising.
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- ground breaking
- english garden
- garden plants