“If you don’t care about plants, you may not know how to take care of another human being” | Science

Hundreds of children visit the Arnold Arboretum, the botanical garden of Harvard University in Boston (USA) every year, where there is a norm: 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 a professor of Evolutionary and Organism Biology at Harvard University and has devoted his entire career to studying the evolutionary diversification of plants.

Question. Plants have been shown to have special relationships and help each other. In that sense, are they better than us?

Answer. From an evolutionary biologist’s point of view, a large number of premature deaths occur 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 have not managed to do so? 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 flower 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 tamed 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 this 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. For twenty years I have been wondering if fathers and mothers are arguing about how to feed their offspring and in the last five years we have discovered …

“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, fathers are sperm donors and mothers are ovules, but they also have to feed. One is more involved than the other, who only gives his genes. This occurs with animals, but also with plants.

P. So what does a father want when he gives his genes to a mother’s seed?

R. That seed has all the food possible. Mothers have many seeds, but they select and reject those that they think are not good because they have limited resources and must decide where to invest their food.

P. And when analyzing those seeds, what else can you see?

R. In molecular genetic studies you can even see how all this happens. Because 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 will she invest in? You will wonder which ones are the best. Females recognize seeds that may be genetically related and shut off pollen arrival biochemically. They are continually filtering parents. It is one of the great stories of plants and I don’t think many people know it.

P. When they reject a 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 parents and thus she can choose. If insects come into play, parents of different origins come to each flower and 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 is incredible. In some cases, they will know if the father is a direct relative; in others they will know if it is not a good match, and then the mothers will stop fertilizing. 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 conversations between parents and make decisions.

P. When did you first become interested in plants?

R. I grew up in the field, 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 hairy pig killed in formalin that we had to dissect. I didn’t like anything. I 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 on.

P. So actually the plants chose you …

R. The truth is, yes, and I feel very lucky to have discovered his 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 one was unimaginable to you when you started studying them?

R. Plants do a lot of weird things. Do you know ginkgo? It is a very old tree present in cities. It has two sexes (those who make pollen, males, and those who make seeds, females), but you will not see them together in Madrid. You will not see any seeds in 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 vomit from the butyric acid inside. The seeds are scattered on the ground and it smells like everyone in the city has vomited there. It is very powerful.

P. And what sense does it make for females to do this?

R. Some extinct animal thought they smelled very good and started eating the seeds to disperse them. The plant stuck with that code, which smells terrible to us, but you can see all kinds of flies, scattering seeds, flying around.

P. It has been their way of adapting and surviving, but plants generally face many threats …

R. Yes, like invasive pathogens that move on wooden pallets carried on ships. Because we move things around the world and sometimes don’t care, we keep introducing threats that could annihilate an entire species. They can be insects, fungi or bacteria in the most unsuspected places, like the soles of my shoes.

P. All this will be worsened by the climate crisis.

R. Of course. Climate change exacerbates the situation. I can give you an example. In the botanical garden we have magnificent beech trees that suffer from a disease caused by an invasive fungus. Trees can fight the epidemic, as you and I do if we are healthy, but what if we are stressed, old, or poorly fed? 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 perished. The disease won. The beech trees were so stressed by the drought that they were unable to fight. 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 or not this concerns us. I think most do, but not those who have the power to make decisions.

P. Why worry about plants, many will ask?

R. Sure, it’s not us. The birds are not us, the insects are not us. If you can’t care about 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 do not, we will lose the ability to feed the world, but I do not think that is the main reason.

“In high school I wasn’t good at Biology, but I had an instinctive and deep connection to 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 must worry because we share the Earth with them.

P. Plants have been adapting for millions of years, but are they still maintaining 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 neither plants nor trees, there was a glacier, and now the city is full of vegetation. Plants move, change, grow, and adapt. However, the changes we are introducing now are so rapid that certain ecosystems will collapse.

P. What will happen? Can’t we go back to the starting point?

R. If it finally goes wrong, it will certainly be our fault. We will not be able to return. It will be a new future.

P. And what will that future be like?

R. I don’t know … Maybe it’ll be one without humans. But I am sure of one thing, and that is that the future will be very rich thanks to evolution. The most incredible thing about life is that it is resilient. Balance can return. We may not be 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. Have you not noticed?

R. Yes, there is an increasing environmental awareness. 40 years ago, when I started my studies, scientists did not speak to the public, they thought it was not part of their work. In the last 20 years science journalism has become a very powerful way to help scientists – who were not good at explaining things – connect with people. Being a scientist is not just doing science. We are citizens in charge of raising awareness.

P. Will we someday know everything about plants?

R. I don’t think so … There is an Alfred Tennyson poem 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 entire universe. But we can not. Each plant is so complicated that it is impossible. That makes nature so wonderful.

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