Every year hundreds of children visit the Arnold Arboretum, the botanical garden of Harvard University in Boston (USA), where there is a rule: everyone is capable of teaching, from university students to staff and scientists .
One of them is the biologist William Friedman, who visited Spain during the Passion for Knowledge (P4K) festival held in San Sebastián. Passionate about plants, Friedman is Professor of Evolutionary Biology and Organisms at Harvard University and has devoted his entire career to the study of the evolutionary diversification of plants.
Ask. Plants have been shown to have special relationships and help each other. In that sense, are they better than us?
Answer. From the point of view of an evolutionary biologist, there is a great deal of premature death among plants. For every bird you see out the window, 199 have died. For each plant you see, how many seeds have fallen or grown a little and didn’t make it? Plants do wonderful things by cooperating with each other, but sometimes they have a dark side.
P. What aspect of plants has surprised you the most throughout your career?
R. I have had incredible surprises throughout my life, especially with the study of the evolutionary origin of flowering plants, which are a very recent group, the youngest. How is it possible then that they are everywhere? I studied the inner tissue of the seeds in which the mothers put their food and which then goes to the embryo. It is something that we have domesticated to eat, the so-called endosperm. We eat a grain of rice or corn because it is full of nutrients. I have discovered many things about this process.
P. Like what?
R. That mothers and fathers disagree regarding the nutritional contribution of that tissue, and we can see it with genetic analysis. When I look at a seed I can see the genes of the mother and those of the father, how they debate about how much food it should have. I have been wondering for twenty years if fathers and mothers argue about how to feed their offspring and in the last five years we have discovered it…
“Can plants adapt to the speed at which we are changing the planet? We’ll find out.”
P. And who wins?
R. Ah [risas]Well, the truth is that it depends. That is the question. In general, the fathers are sperm donors and the mothers are egg donors, but they also have to feed. One gets more involved than the other, which only gives her genes. This happens with animals, but also with plants.
P. So what does a father want when he gives his genes to a seed from the mother?
R. May that seed have all the food possible. The mothers have many seeds, but they select and reject the ones they think are not good because they have limited resources and must decide where to invest their food.
P. And when you analyze those seeds, what else can you see?
R. In molecular genetic studies you can even see how all this happens. Since they make different investments, fathers are selfish and mothers try to make universal decisions. If a mother with a hundred seeds only has food for fifty, which ones is she going to invest in? She will wonder which are the best. The females recognize the seeds that may be genetically related and close the arrival of the pollen biochemically. They are continually filtering parents. It’s one of the great plant stories and I don’t think many people know about it.
P. When they reject one parent, can they choose another?
R. In the case of pines, which pollinate by means of the wind, the mother receives the sperm of many fathers and thus can choose. If insects come into play, parents of different origins come to each flower and the mothers make them compete with each other.
P. But how do they know if they are good parents?
R. They know the genetic attributes of the father, it’s incredible. In some cases, they will know if the father is a direct relative; in others they will know if he is not a good match, and then the mothers will stop fertilization. And even when fertilization has started they can abort the seeds. For many years I have enjoyed understanding that plants, like humans and other animals, have parental conversations and make decisions.
P. When did you become interested in plants?
R. I grew up in the country, but it was in high school biology classes that I became most interested. It wasn’t good, but I liked it so much… One morning we were in the lab and we had a dead hairy pig in formalin that we had to dissect. I didn’t like it at all. He had no idea how animals worked. So I thought I probably shouldn’t be a biologist. [risas]. But suddenly the plants appeared and I felt an instinctive and deep connection with them. I was very lucky to experience that feeling with the plants and move forward.
P. So the plants actually chose you…
R. The truth is that yes, and I feel very lucky to have discovered your world [Risas].
Plants do wonderful things by cooperating with each other, but sometimes they have a dark side.”
P. Of all the characteristics of plants, which of them was unimaginable to you when you began to study them?
R. Plants do a lot of weird things. Do you know the ginkgo? It is a very old tree present in cities. It has two sexes (those that make the pollen, the males, and those that make the seeds, the females), but you won’t see them together in Madrid. You will not see any seeds around the city and the reason is that they smell very strong, so people only plant males. In the Harvard Botanical Garden we have females and they smell like vomit due to the butyric acid inside them. The seeds are scattered on the ground and it smells like everyone in town has vomited there. It is very powerful.
P. And what’s the point of females doing this?
R. Some extinct animal thought they smelled really good and started eating the seeds to disperse them. The plant stuck with that code, which smells horrible to us, but you can see all kinds of flies, which disperse seeds, flying around.
P. It has been their way of adapting and surviving, but in general plants face many threats…
R. Yes, like the invasive pathogens that move on wooden pallets transported on ships. As we move things around the world and sometimes we’re not careful, we keep introducing threats that could wipe out an entire species. They can be insects, fungi or bacteria in the most unexpected places, like the soles of my shoes.
P. All of this will be made worse by the climate crisis.
R. Of course. Climate change aggravates the situation. I can give you an example. In the botanical garden we have magnificent beech trees that are suffering from a disease caused by an invasive fungus. Trees can fight the epidemic, as you and I do if we are healthy, but what happens if we are stressed, we are old or we eat poorly? In this sense, plants are exactly the same as humans. Three years ago we had the worst drought in the area. For two months we suffered from arid conditions and in the following two years, the diseased trees eventually perished. The disease won. The beech trees were so stressed by the drought that they could not fight back. We had to cut down three meter wide trees that had died. And this is being seen with insects and birds all over the world. The question is whether this concerns us or not. I think the majority yes, but not those who have the power to make decisions.
P. Why worry about plants, many will ask?
R. Sure, they’re not us. The birds are not us, the insects are not us. If you can’t care for a plant, you may not be able to care for another human being. It is said that we should care about nature because if we don’t we will lose the ability to feed the world, but I don’t think that is the primary reason.
“In high school I was not good at Biology, but I had a deep and instinctive connection with plants. I could understand them through the microscope”
P. And what would it be?
R. To think that all these organisms are our food and depend on our exploitation is to be short-sighted. There is a deeper value. We should care because we share the Earth with them.
P. Plants have been adapting for millions of years, but do they still maintain that capacity now?
R. Plants can adapt, yes. Can they do it quickly? Yes. Can they adapt to the speed at which we are changing the planet? We’ll find out. 20,000 years ago in Boston there were no plants or trees, there was a glacier, and now the city is full of greenery. Plants move, change, grow and adapt. However, the changes that we are introducing now are so fast that certain ecosystems will collapse.
P. What will happen? Can’t we go back to square one?
R. If it ultimately goes wrong, it will certainly be our fault. We won’t be able to go back. It will be a new future.
P. And what will that future look like?
R. I don’t know… Maybe it will be one without humans. But I am sure of one thing, and that future will be very rich thanks to evolution. The most incredible thing about life is that it is resilient. The balance can return. Maybe we are not resilient enough, but in millions of years the planet may still be green and still have animals. If we want to remain part of it, we have to be more careful.
P. We may now be starting to change. Haven’t you noticed?
R. Yes, there is more and more environmental awareness. 40 years ago, when I started my studies, scientists did not speak to the public, they thought that it was not part of their work. In the last 20 years science journalism has become a very powerful way to help scientists – who weren’t good at explaining things – to connect with people. Being a scientist is not just doing science. We are citizens in charge of educating others.
P. Will we one day know everything about plants?
R. I don’t think so… There is a poem by Alfred Tennyson called Flower in the Crannied Wall from 1863 which is the answer to your question. If I could fully know each of the plants, I would know the whole universe. But we can not. Each plant is so complicated that it is impossible. That makes nature so wonderful.