A seed usually has a little package of nutrients called the endosperm, which feeds the baby plant while it’s establishing itself. All of this is sealed inside a durable shell that lets the seed stay viable for a long time until conditions are just right to germinate or sprout. Some seeds also have adaptations to help them find a good place to grow. Ideally, somewhere far away from their parent plant so they aren’t directly competing for light or nutrients. That’s called dispersal, and that’s where you came in when those burrs hitched a ride on your clothes. A seed grabbing on to a passing mammal is one thing, but some plants try to give their seeds the best possible start in life in ways that are a little more extreme.
Okay, seeds, you may be saying to yourself. Little things that come in paper packets for a buck-fifty. How’s she going to make this interesting? No effort required at all. There’s more on heaven and earth than are dreamed of in your philosophy. Let’s start small. The smallest seeds in the world belong to orchids. They’re not much bigger than a speck of dust, literally, only about 50 microns or 5/100 of a millimeter across. In terms that are easier to visualize, the finest human hair is about 17 microns across. Also, microns and micrometers are the same thing, I just learned. With orchids, it’s all about quantity. One tropical species can contain almost four million seeds per plant. Tiny and light is the way to go for orchids because they are dispersed by the wind. The lighter you are, the farther you can go,the less likely you are to compete with the parent plant for resources. The seed coat is only one cell thick and it traps air inside to form a tiny balloon around the soon-to-be plant, which lets the seed travel even farther through the air, and as an added bonus allows them to float. Individual seeds from one species were found hundreds of miles from the parent plant. You’d be forgiven thinking orchids must spread like dandelions, but orchids are epiphytes, plants that grow on other plants, usually a tree. And they need mycorrhiza fungus for their roots. Finding the right kind of tree *and the right kind of fungus severely limits how many seeds will become new orchids, hence the massive number.
On the opposite side of the seed size spectrum is the coco de mer, or coconut of the sea. Found only in the Seychelles, an archipelago off the east coast of Africa, coco de mer palms produce the largest and heaviest seeds in the plant kingdom. Which also amusingly looks like a shapely zaftig butt, from which they get their nickname love nut. How big are these thicc bois? Up to 1.5ft/.5m long and weighing as much as 88lbs/40kgs. It takes 6-10 years for the fruit containing this seed to ripen. Once they drop from the tree, hopefully not on anyone, the seeds take another two years to germinate. The coco de mer palms put far more of their resources into seed production than other palm trees. Their huge leaves also act as rain funnels, providing a steady source of water and flushing nutrient-rich organic material to the base of the plant. We know how the seeds get so big, but do we know why? Researchers think the dense, shady conditions and a lack of animal seed dispersal informed their evolution. The seeds of their mainland cousins are spread by elephants, but you don’t really get elephants in the Seychelles. When not relying on animals for dispersal, there’s no need for the plant to keep its seed at an edible size. Bonus fact: avocado seeds are so huge because they used to be distributed by prehistoric ground sloths. If only there was some way to tell the plants to get with the times. For tiny new coco de mer trees, competition for light is intense, so huge seeds means more fuel to keep the young plants going until they grow tall enough to access the sunlight. Sadly, and you can probably finish this sentence for me, the coco de mer is endangered, not only from the usual pollution and land-clearing, but because people keep taking the seeds as souvenirs. There are only about 9,000 coco de mer trees left.
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We’ve already touched on seed dispersal a bit. It wouldn’t matter how well-designed a seed was if it had no way to get where it was going. You’re probably familiar with a few methods already. Some plants rely on the outsides of animals, as anyone that’s every pulled burrs from their pet’s coat or their socks can tell you. Many plants rely on their fruit being eaten by animals to move their seeds about. Some plants want their seeds to be dropped as the animal eats, but some are counting on them being dropped *afterwards, so the seeds have tough enough outer coats to protect them from the digestive processes. Other seeds actually *require digestion in order to sprout. The hard seeds of blackberries, for example, only wake up from dormancy after being abraded in a bird’s gizzard. Stomach acids and digestive enzymes break down hard seed coats to make the seeds more permeable to water. And, of course, being deposited in a steamy pile of fertilizer doesn’t hurt either.
Birds and mammals don’t have the market cornered on seed dispersal. In South America, the tucum palm actually relies on a fish. A fruit-eating fish. I need a minute to absorb that concept. Tucums grow in the largest freshwater wetland in the world in a Brazilian section of the Amazon rainforest. Annual rainstorms flood the region and that’s when the tucum palm drops its fruit. And the pacu fish are waiting. For those unfamiliar, pacu are a giant cousin to the piranha, with bizarre and unnecessary human-looking teeth. Pacu love the palm fruit so much that fishermen use it as bait. Scientists weren’t sure if the pacu were doing much to spread seeds or if the fruit-eating was just because. Over several seasons, a team of ecologists checked the guts of 70 fish and found that nearly 3/4 had at least one seed in their digestive tract. One fish had eaten more than 140 seeds, many of which were still intact, meaning they’d be able to sprout after the fish pooped them out and the floodwaters eventually receded. The scientists also checked the feces of other animals that live around the palms, but no intact seeds were found. Either the palm fruit wasn’t a popular menu item or the seeds didn’t survive the digestive tracts of terrestrial animals. This paragraph is going to take the same turn as the coco de mer. Humans are over-fishing the pacu, especially the biggest fish, which are the ones that can eat and distribute the most seeds. If the pacu go, that could spell real trouble for the tucum palms that depend on them.
But why rely on birds and fishes, when you can have seed babies that fly? Equipped with parachutes or wings, gliders, or helicopters, a diverse group of plants have adaptations for wind dispersal. For example, each tiny dandelion fruit has a feathery “pappus” to help it catch a breeze. Side note: yellow dandelions are the first source of nectar for bees in many areas each spring, so please don’t be in such a hurry to mow them. Maple “whirlybirds,” which are so fun to toss in the air and watch spiral down, are winged fruits called samaras. Other seeds have papery edges and even wings to help them disperse. The seeds of the climbing alsomistra gourd of the Malay archipelago have a wing-span of 5in/12cm across.
Animal seed dispersal may seem like a system in which the plants are a passive participant and the animals are active. There is a system in which the plants actually take the lead.
To tell us more about that, please welcome my guests Jennifer and Amber from Better Than Human.
Some plants scatter their seeds with a real bang. By the bright blue Mediterranean sea, there’s a plant that disperses its seeds super-soaker-style. It’s called, completely maturely and in no way prurient or amusing, the squirting cucumber. [beavis and butthead] Picture a fuzzy gherkin hanging from the top of a flower stalk about a foot high. When a squirting cucumber ripens, the slightest vibration causes it to shoot off of the stem, spraying out seeds in a jet of goo, as much as 20ft/6m away. You really have to see it to believe it; link in the show notes.It’s an example of an unusual adaptation called rapid plant movement, like a Venus Fly Trap closing its jaws. Plants don’t have muscles like animals do, but they do have rigid cell walls. These can hold back high water pressure and that’s what’s at work here. The squirting cucumber’s explosion is a one-time event powered by the release of pressure that builds up inside the fruit as it ripens and fills with liquid. The squirting cucumber *is actually related to the cucumbers in your salad and gardeners plant it as a novelty, but don’t try to eat one as they are poisonous.
To stay safe from squirting cucumber, all you have to do is not eat it. To stay safe from the South American dynamite tree, you’ll need to stay about 140gt/45m away. Its seed cases are shaped like little decorative pumpkins. As they dry out, the individual ridges holding the seeds start to shrivel. They shrink so much that they break away from the seed case’s central axis and suddenly the whole thing explodes with a bang like a gun-shot. The inch-long seeds fly out at speeds of 230ft/70m per second. Despite this inherent danger, people plant them as shade trees in the tropics. Guess you have to take the bad with the good. But how efficient a method is an exploding seed case? Scientists used high-speed photography to measure the velocity and angle of the seeds and found that the shape and angle of the seed capsules gives the seeds maximum range, like startling little botanical frisbees.
Speaking of frisbees and other fun games and toys, thanks to Greenbrier games for donating prizes for the latest round of trivia. It’s getting increasingly hard to come up with questions that are just the right level of difficult, so I’m moving trivia to an every other week format.
We’ve done smallest, biggest, fastest, how about oldest seed? Let’s add one condition there, because archeologists have found seeds with prehistoric animals and cave dwellings. What is the oldest scene that’s actually germinated? I can’t store seeds properly for a year, so it really impressed me that Israeli scientists were able to sprout a date palm seed that’s about 2,000 years old. That upsets the previous record-holder, a lotus found in a dry lakebed in China, by about 700 years. The date seed was one of several found in the 1960s by archaeologists excavating Masada, a fortress in the Judean Desert destroyed by the Romans in 73CE. In 2005, three seeds were planted at the Louis L. Borick Natural Medicine Research Center. No reports as to why then and not sooner. Of the three, one seed germinated. It didn’t just sprout, it grew. Three years later, the palm was a healthy three feet tall. The team named the tree Methuselah, after the biblical figure who lived to be 969. When the tree was moved to a bigger pot at 15 months, they retrieved fragments of the shell and radiocarbon dating showed that it dates from the time of Masada. It makes sense when you say the dry conditions of the desert preserved the seeds, but how does it actually do that? The lack of humidity reduces the generation of free radicals, which would cause oxidation.
[news sting] This just in. Methusaleh is NOT the oldest viable seed plant. It’s been beaten by 30,000 years. A Russian team discovered seeds of Silene stenophylla, a flowering plant native to Siberia, buried by an Ice Age animal near the banks of the Kolyma River. Radiocarbon dating confirmed that the seeds were 32,000 years old. The seeds were found 124ft/38m below the permafrost, surrounded by the bones of mammoths, bison, and woolly rhinoceros. There were both mature and immature seeds. While the mature seeds were damaged, there was still viable material inside the immature seeds. The team extracted that material from the frozen seeds, placed it in vials, and successfully germinated the plants, according to a new study. The plants grew, flowered, and, after a year, created seeds of their own, which is a sentence I feel disproportionately happy reading. As the plants grew, the researchers saw that the flowers of the ancestral plant were a different shape from the modern stenophylla flowers.
Speaking of surprises being revealed, I’ve got one coming up for you. I’ll be doing an unboxing video soon. What could a podcaster be unboxing, you might well ask? I won’t say yet, but you’ll have a chance to win one. In the meantime, hop over to the social media (urls) to answer a poll about the most convenient time for the livestream to take place. I want as many people as possible to have a chance to win. And while you’re there, remember that word of mouth, or in this case word of mouse, is still the best way to help your favorite podcast.
There are many organizations around the world who have taken up the banner of seed preservation, nearly 2,000 in fact. Most of us have heard of the seed vault at Svalbard, the cool-looking tower sticking out of a Norwegian mountain, where the permafrost ensures the seeds are preserved without need for electricity. Incoming Futurama reference.
If you don’t want to go quite so far north, perhaps fly to Old Blighty and visit the Millennium Seed Bank at Kew Gardens in London. In 2009, they reached their goal of preserving and cataloging seeds from all of the UK’s native plant species, with the odd exception for things that don’t store well. They also work with a network of nearly 100 other seed banks to preserve species in situ, where they are, and to provide back-up samples in case the specimen at any one seed bank is compromised. Alongside the three attractive glass buildings, which house the collection, a lab, and the public exhibit space, and really is quite fetching, there are raised garden beds, each an example of a threatened landscape in Britain. If there was a seed bank that looked like a nice day trip, Kew Gardens would be it.
It’s not the most important seed bank, though, or the bank that has given its collection the most protection. For that, we have to go back to WWII, and an abrupt shift in tone. In September 1941, German forces began to push into Leningrad, before and since called St Petersburg. They laid siege to the city, choking off the supply of food and other necessities to the city’s two million residents. The siege of Leningrad didn’t last a month, or two, or even six. The siege lasted nearly 900 days. Among the two million Soviet citizens struggling to survive were a group of scientists ready to make the ultimate sacrifice for the good of mankind. While they did, their leader, Nikolay Vavilov, Russian geneticist and plant geographer, lay dying in a Soviet prison a thousand miles away.
Vavilov had travelled the world on what he called “a mission for all humanity.” Vavilov led 115 expeditions to 64 countries, to collect seeds of crop varieties and their wild ancestors. Based on his notes, modern biologists following in Vavilov’s footsteps are able to document changes in the cultural and physical landscapes and the crop patterns in these places. To study the global food ecosystem, he conducted experiments in genetics to improve productivity for farmers. “He was one of the first scientists to really listen to farmers – traditional farmers, peasant farmers around the world – and why they felt seed diversity was important in their fields,” says Gary Paul Nabhan, ethnobiologist and author of ‘Where Our Food Comes From: Retracing Nikolay Vavilov’s Quest to End Famine’, continues: “All of our notions about biological diversity and needing diversity of foods on our plates to keep us healthy sprung from his work 80 years ago.” His hope was that one day science could work with agriculture to increase each farm’s productivity and to create plants that would grow in any environment and bring an end to hunger. As Russia fought to find its way through undergoing revolutions, anarchy, and, most importantly to Vavilov, famines, he went about storing seeds at the Institute of Plant Industry, also known as the Pavlovsk Experimental Station. The scientists there collected thousands of varieties of fruits, vegetables, grains, and tubers. Unlike Svalbard and Kew Garden, the seeds a Pavlovsk weren’t just stored as seeds, but some were perpetuated as plants in the field. This is because some varieties do not breed true from seeds, so can’t be stored as seeds to get those plants in the future.
There was one obstacle in Vavilo’s way. Two, really, but one was much greater a threat, that being Joseph Stalin. The other threat was Stalin’s favorite scientist, Trofim Lysenkoly. Lysenko was a dangerously mis-informed scientist. Rather than survival of the fittest, where the genes that help an organism survive long enough to reproduce are the ones that are passed on, Lysenko believed that organisms could inherit traits the parent acquired during its lifespan. Instead of believing that the giraffe with the longest neck was able to reach the food and live to have babies, he believed that the giraffe stretched its neck up and its baby would have a longer neck because of that. He also believed that if you grafted a branch from a desirable tree onto a less desirable tree, the base tree would improve. His theories about seeds and flowers were equally backwards. It was garbage science at best. At worst, well, we don’t need to speculate on that. We saw it happen. Crops failed under his now-mandatory systems on the new collectivized farms, which themselves reduced productivity. Lysenko’s policies brought on a famine. But he was in Stalin’s favor and in the Soviet Union, that was all that mattered. In August 1948 when the Politburo outlawed the teaching of and research into classical Mendelian genetics, the pea plant-based genetics we learn about in middle school. This disastrous government interference in the face of widely-accepted science and its outcomes are called the Lysenko Effect.
There was no way Stalin’s favorite scientist was going to take the fall, so Stalin singled out Vavilov, who had been openly critical of Lysenko. He claimed Vavilov was responsible for the famines because his process of carefully selecting the best specimens of plants took too long to produce results. Vavilov was collecting seeds near Russia’s border when he was arrested and subjected to 1700 hours of savage interrogation. World War II was in full swing and it was impossible for his family to find out what had happened to him. Vavilov, who spent his life trying to end famine, starved to death in the gulag.
Back in Leningrad, some scientists from the Institute of Plant Industry were able to get the bulk of the tuber collection, and themselves, to another location within the city. A dozen of Vavilov’s scientists stayed behind to safeguard the seed collection. At first, it seemed as though they’d only have to contend with marauding enemy troops breeching the city, seeking to steal the seeds or simply destroy the building. The red army pushed the Germans back as long as they could. Nothing moved in or out of the city. “Leningrad must die of starvation”, Hitler declared in a speech at Munich on November 8, 1941. As the siege dragged on, the scientists then had to contend with protecting the seeds from their own countrymen. Food was rationed, but once it ran out, people ate anything they could to survive–vermin, dogs, leather, sawdust, and as so often happens in such dark hours, some at the dead. The scientists barricaded themselves inside with hundreds of thousands of seeds, a quarter of which were edible just as they were, along with rice and grains.
But they did not eat them. They took turns guarding the store room in shifts, even as they grew weaker, even as they heard the Germans looting and destroying out in the streets. The only thing that mattered was guarding the collection, safeguarding both the botanical past and future for mankind, and the work of their fallen Vavilov. One by one, the scientist began to die of starvation. One man died at his desk; another died surrounded by bags of rice. In the end, nine of the twelve scientists did not live to see the end of the siege. But not a single grain, seed, or tuber was eaten. According to Nabhan, “One of them said it was hard to wake up, it was hard to get on your feet and put on your clothes in the morning, but no, it was not hard to protect the seeds once you had your wits about you. Saving those seeds for future generations and helping the world recover after war was more important than a single person’s comfort.”
Unlike many of the 85 million deaths in WWII, those nine scientists’ lives were not wasted. Today, many of the crops that we eat came from cross-breeding with varieties the scientists saved from destruction. As much as 80% of all the pre-collapse Soviet Union’s fields were sown with varieties that originated in Vavilov’s collection. It’s a sad tale, I know, but also an amazing one that so few of us hear. Which is odd when you consider the thousands of hours of WWII documentaries out there. The world nearly lost Vavilov’s collection a second time, though. In 2010, the land it sits on was being sold to a developer who planned to build private homes on the site. The collection can’t just be moved; there are all sorts of complex legal and technical issues, including quarantines. The public called for the site to be preserved and in 2012, the Russian government took formal action to prevent the land from being conveyed to private buyers. As far as I can find, it stands safely still.
And that’s…Back to the handle watermelon. Even if Art Combe had wanted to know how old the seeds he found were, the technology to date them didn’t yet exist. Of the two hundred-ish seeds in the bottle, only about twelve germinated. They were unlike any watermelon Combe had ever seen, a round watermelon that tapered at the end into a perfect handle, possibly bred into the plant for easy transport. But people wouldn’t want to buy weird-looking melons, so Combe crossed them with modern melons. Still, rogue handles would appear. Luckily for the variety, Combe shared some of the original seeds with a friend of his, Cliven Bundy who bred the line faithfully and shared seeds with neighbors for thirty years. Bundy later got in a dispute with the federal government over grazing his cattle on public land, got in a stand-off with them in 2014 and whose son Ammon took over the Malheaur National Wildlife Refuge in 2016, but that’s another show. Stay tuned for another podcast you might enjoy. Remember… Thanks…