Last week, we posted Jonathan Drori’s fascinating short talk about the Millennium Seed Bank — a massive effort to preserve the world’s threatened plant life within a global network of seed archives. It’s a big topic to cover in 3 minutes, so the TED Blog asked Drori if he had time to answer a few more questions — like, How do seeds die? He happily obliged. (In the photo above, Drori is on a collecting trip looking for rare bamboo.)
Where’s the Millennium Seed Bank, and what happens there?
The Millennium Seed Bank is part of the Royal Botanic Gardens, Kew, spread across two sites in southeast England. We have a large group of scientists researching botany, plant biodiversity and restoration ecology, as well as operating the enormous and internationally known gardens themselves, which are of course, living scientific collections.
And what do you do there?
My role is as a main-Board Trustee. There are 12 of us, responsible to the nation for ensuring that the strategy and operations of the organization are excellent. My own particular interests are in our use of technology and the web, in public understanding of our scientific work and in education, outreach and marketing. I also spend some time fundraising; though Kew itself is about half-funded by the UK government, the Millennium Seed Bank is financed from other sources, including philanthropic organizations and business sponsors.
You mention in your talk that the seed bank does some high-tech things with the seeds. What are a few examples?
Kew has a project that uses gas chromatography-mass spectrometry to analyze the air just above the stored seeds. The aim is to identify and quantify the volatile organic compounds that are released by dry seeds during long-term storage. Seed species that can be stored successfully long-term will be compared with some species that suffer damage during storage (“recalcitrant” seeds) and are less able to germinate as a result. The aim is to see if there are volatile marker compounds that could be used as non-invasive real-time monitors of the long-term viability of seeds in seed banks. The results from the project could additionally have implications for horticulture, in terms of a non-invasive method for rapidly assessing the health of seeds.
Can you talk a little bit about the search for viability markers? What are some of the possible genetic and molecular clues that a seed might be viable?
Ilse Kranner is one of our experts on seed viability. She and her colleagues are looking for chemical or other indicators of cell death. Her detection methods look for these indicators either directly or through the switching on or off of genes. The Holy Grail is to find a universal, non-destructive, rapid technique — a tall order!
Seeds do give us some molecular clues that allow us to diagnose their viability. We use methods of gas chromatography-mass spectrometry and HPLC (high-performance liquid chromatography) to analyse what goes wrong when a seed dies. An example is Kranner and her colleagues’ work on antioxidants in seeds. Antioxidants mop up “free radicals” (these are the villains that can destroy big molecules such as DNA, RNA, lipids and proteins). Some of these antioxidants used by plants turn out to be important vitamins for humans, e.g. vitamins C and E. The team has found that antioxidants help the seed to survive stress, but when aging conditions (high temperatures at high seed water-content) persist, the antioxidant system eventually breaks down. Calculating how powerful these antioxidants need to be to counteract the seeds’ stress allows us to predict whether or not a seed will die upon water uptake, or if it will germinate and form a new seedling.
There are also indicators of “programmed cell death.” This is a program of cellular suicide at the end of which a cell cuts up its own DNA into very small fragments that cannot be re-assembled again. Programmed cell death has evolved because it is better for an organism to destroy a cell that is damaged beyond repair rather than putting energy into sustaining it. Also, cell division must be balanced by such processes, otherwise there would be tumor-like growth. The team has found such DNA fragments in dead seeds, and these fragments tell us that many (or all) cells in a seed have undergone programmed cell death as the seed aged. So these fragments may lead us to a useful indicator of seed viability.
How long do the seeds last?
Seed longevity is extraordinarily variable — by at least four orders of magnitude. Seeds from plants that grow in cold, wet places tend to have shorter lives — just a few years in some cases, such as the wood anemone. At the other extreme, plants that have evolved in hot, dry places such as eucalypts and some grains tend to have the greatest longevity –- probably thousands of years.
Can you grow plants from the stored seeds just by warming them up and adding water?
In some cases, yes. Many seeds, though, are very fussy. They need special combinations of temperature, moisture and the right timing to get them to germinate. Sometimes they need a particular cycle of conditions before they’ll sprout. One of the very worrying aspects of climate change is that these precise conditions may not occur, which would mean that whole populations of plants could die out if they cannot adapt quickly enough. Our research gives us germination protocols, sets of rules and methods for storing and germinating every species, and we make these freely available. These germination protocols are already being used by farmers to increase the yields they get on cultivated crops.
In the seed bank’s work in the field, how often do the collection teams discover unknown plant species or variants?
In places like Madagascar, fairly frequently — we probably have 20 or so species thought to be completely new to science, collected over the past five years. Elsewhere, the species may be well known and documented, though not collected or preserved. About 1,000 of our seed collections have not yet been identified — many of these will be new to science, but we won’t know for sure until the relevant experts have a look at them.
READ MORE: Jonathan Drori talks about how hard it is to choose a favorite plant, collecting seeds in the Andes, and remembering exactly how important plants are.Does the collection involve just seeds, or do the collection teams also preserve whole plants?
We collect seeds (average of 32,000 seeds per collection), herbarium (dried, pressed) specimens for identification purposes and lots and lots of data (geology, soils, location etc.).
After the germination tests every 10 years, what do you do with the little plants? The gardeners among us want to know.
We carry out germination tests on all the collections that come in to the Seed Bank — more than 10,000 germination tests per year — and we test for viability every 10 years. Many of the resultant seedlings are destroyed. We wouldn’t have the space to grow them, and letting them all loose in the UK could distort our own ecosystem. Rare plants are grown on to maturity to produce more seeds and for reintroduction. Other seeds are grown on for identification purposes, for research and even for public display.
Do you have some favorite plants in the seed bank? Or some favorite seed-collecting stories?
That’s a bit like asking a parent which is their favorite child! Personally, I revel in the sheer diversity, not just of the plants to which the seeds will give rise, but the sheer, crazy variety of the seeds themselves. Every possible shape and color. They’re amazing things. Having said all that, I’m pretty keen on the Adansonia family (baobabs). Fantastic seeds and fabulous, incredibly important trees with so many uses. I also asked Dr. Paul Smith, director of the Millennium Seed Bank and he responded, “Too many to mention! Cylindrophyllum hallii — down to six plants left in the wild in South Africa. Banksia brownii, reintroduced to Western Australia from the seed bank. Wollemi pine (NSW, Australia). Bromus interruptus — European grass extinct in the wild, recently reintroduced. Leucospermum sp.: 200-year-old seed germinated in 2007 from seeds in an old wallet, and now a healthy shrub.”
During a seed-collecting trip to the Andes last year, I saw the most amazing bird I’ve ever seen in my life, which I now know to be one of the world’s largest hummingbirds –- a truly remarkable creature. Almost speechless, and keeping my voice low, I pointed at it and asked one of the Chilean plant-scientists with us what we were looking at. He appeared puzzled for a moment, then brightened, “That’s a fantastic plant -– quite rare though it’s not much to look at — it’ll be easier to see once that distracting bird gets out of the way.”
If you’d had another 2 minutes onstage, what would you have said?
I want to thank the people all over the world who’ve been part of this amazing project, which has been led by Dr. Paul Smith and his team: The network of botanists and volunteers all over the world who are painstakingly collecting seeds, preparing them, storing some locally and sending some to us for safekeeping and research. Then there are the people who work in the (rather chilly!) Millennium Seed Bank itself and partner seed banks around the world. Then there are the researchers who use the seeds and the increasing number of scientists and ecologists all over the world who are using seeds for research and restoration. I’d like to thank the government ministers, politicians of every persuasion, all over the world who have had the wisdom, foresight and imagination to sign the treaties that have made the work of the Millennium Seed Bank possible. And I desperately want to thank our funders, the philanthropic organizations and commercial sponsors who have had the foresight and sense of global responsibility to believe in the project, not only to preserve key crop species but plants that have, so many, many uses for the future -– for all our futures.
That’s a very positive message. What’s the limiting factor to the Seed Collecting and restoration work?
Money, I’m afraid. We need about $10m/year, which seems so little to pay for such a very valuable thing, yet so hard to raise in this (economic) climate! I know that human beings are emotional animals and that people respond best to stories. I’m constantly trying to persuade my scientific colleagues occasionally to drop scientific Latin names (which are important because they properly define and classify a species) in favor of common names which capture the imagination and give us clues to uses that might otherwise be forgotten. Actually, we have a whole other project collecting the folk-tales around plants, some of which have led to remarkable scientific discoveries, but that’s a whole other story, maybe for another TED …
A final word?
Just remember what plants do. Plants use sunlight to photosynthesize. They remove carbon dioxide from the atmosphere to make the solid stuff of which trees and greenery are made. Only plants do this. They make structures and chemicals that give us shelter, provide clothing, food and medicines, stabilize the environment and even give us spiritual sustenance. All human life depends on plants. Don’t ever forget that.