The author

Florianne Koechlin, born 1948, is trained in biology and chemistry and authored and edited several books on plant behaviour: Zellgeflüster, PflanzenPalaver, Mozart und die List der Hirse, and Jenseits der Blattränder. She made many interviews with researchers, farmers, philosophers, and scientists who are working to unravel the secrets of plants. In her role as a former member of the Federal Ethics Committee on Non-Human Biotechnology (ECNH), she has extensively discussed the topic about how the new insights could affect our relationships to plants. www.blauen-institut.ch.

The translator

Thomas Rippel, born 1988, studied environmental sciences at the University of Melbourne and international business at the University of Nottingham Ningbo China. In 2012 he started a vocational training to become a biodynamic farmer. He is a writer on sustainable agriculture on his blog SwissBioFarmer.com, and he published articles and made translations of academic papers. Thomas Rippel currently resides in Zug, Switzerland. He was assisted by Mary Ann Richardson (MPH, DrPH).

E-book edition 2015

English translation copyright © 2015 by Thomas Rippel

All rights reserved

Cover design by Thomas Dinner, Basel

Cover illustration by Florianne Koechlin

www.lenos.ch

ISBN 978 3 85787 939 5

Contents

Introduction

1. Communication skills of the lima bean

2. The language of signals and fragrances

3. A plant is many

4. Plants can smell, taste, see, feel touch, and maybe even hear

5. The hidden social life of plants

6. WWW – the Wood Wide Web

7. The Secret Life of Plants and the esoteric trap: a commentary

8. Are plants intelligent?

9. We are related to plants

10. And our responsibility?

Appendix

Rediscovering Plants. Rheinau Theses on the Rights of Plants (2008)

Breeding as a dialogue. Rheinau Theses on Organic Plant Breeding (June 2011)

Introduction

Plants use fragrances to communicate above and below ground. With a language of “fragrances”, they warn each other of pests and drought and purposefully attract beneficial insects. They coordinate their own behaviour and engage in lively relationships with the environment and peers. Not only do plants support relatives, harass strangers, and make alliances, they also learn from and remember their experiences. Information and nutrients are exchanged among plants through a vast, underground root and fungal networks – a plant internet of unimaginable size.

This fantastic world of plants has drawn me under its spell and is my reason for embarking on a journey to find people working to uncover the secrets of plants.

I have met researchers studying the striking abilities of plants for language by analyzing plant hormones and fragrances. Following rigorous standards of academia, their experiments with leaf-eating robots have identified over one hundred fragrances used in communication by the lima bean. I visited researchers examining the complex relationship networks in soil. Their evidence shows that the millet does in fact feed neighbouring flax plants with sugar compounds. Other researchers discovered that plants respond to sound waves produced by chewing caterpillars and defend themselves. Are plants really capable of listening?

Many scientists regard the plant as a type of biological automaton with pre-programmed, genetically determined reactions. With many recent discoveries, however, such explanations can no longer suffice. A plant is more than an automaton, and we are just at the beginning of this journey to find out just how much more.

New findings are slowly filling the gaps in our ecologically based world view. This suggests that everything is in one way or another linked with everything else; nothing works in an isolated way; and genes do not in fact play an overarching role in the processes of life. Thanks to unprejudiced observation and improved analytical tools and experiments, we are gaining insights into the infinitely complex and dynamic networks that make up life.

But what is the point of knowing that all of us – plants, animals, and humans – are involved in co-evolutionary processes and interdependencies? What does this idea of interconnectedness mean for agriculture, now facing enormous challenges with climate extremes, eroded soils, and finite resources for increasing human demands?

At the end of my journey, one question arose: Why are plants valued so differently from animals in our society? At least “higher” animals are no longer viewed as objects. They have certain rights, and regulations are in place for species-appropriate animal husbandry. Do not plants deserve respect and rights also?

This book contains a collection of interviews and articles from my German books PflanzenPalaver (2008), Mozart und die List der Hirse (2012), and Jenseits der Blattränder (2014), as well as a few new texts.

Florianne Koechlin, October 2015

1. Communication skills of the lima bean

Plants communicate with their environment, especially by using fragrances. They converse with their peers and insects, and even other animals. They create different fragrances to chat with many different partners.

A research team led by Wilhelm Boland at the Max Planck Institute for Chemical Ecology in Jena examines the communication skills of the small lima bean. I visited him a few years ago.

He says that plants possess a large repertoire of different fragrances. “So far we know about a thousand fragrant compounds. There could be more.” He sees my amazement and to put it into perspective adds: “Not all fragrances are present in one plant. Five to ten of these chemical fragrance compounds, however, are common to all plants. In addition, each plant can produce many different trace components.”

Would it then be correct to say that a common language exists among plants, along with many dialects characteristic to each species? Wilhelm Boland laughs. That might be a bit of an exaggeration, but yes, one could see it that way. It is important, he continues, how and in what quantities the fragrances are mixed together because different “dialects” arise from slightly different formulations of chemical odour molecules.

A good example of this is the lima bean. Wilhelm Boland says that when a caterpillar starts feeding on a leaf, many things happen. The physical damage itself releases a cloud of fragrances. This fragrance warns the whole plant of the impending danger, and all the leaves begin producing chemicals for defence. The fragrance mixture is like an “express highway” of information, enabling immediate dissemination of information. Neighbouring plants also understand the message and start defensive measures.

“This response is only the first line of defence,” he says, “more will follow immediately. After three to four hours, the lima bean produces a new fragrance bouquet to specifically attract beneficial insects to combat the bean’s predators. So the bean calls in her bodyguards, so to say. What is very interesting is how the lima bean can tell not only that she is getting hurt, but she also knows exactly who is hurting her.” When the lima bean is being infested by spider mites, she releases a special scent to attract predatory mites that feed on the spider mites. If caterpillars are attacking the lima bean, she sends out a slightly different fragrance to attract parasitic wasps that lay eggs inside the caterpillars. The eggs then hatch into wasp larvae and eat the caterpillars from within.

How can the lima bean tell if she is being attacked by a spider mite and not a caterpillar? She recognizes the saliva of the insects, says the researcher. “By now we know many of the chemical compounds of the insect saliva that enable the plant to determine exactly which enemy is attacking her.”

So the plant “tastes” the saliva of the predator eating away at her and then produces the fragrance that attracts the right “bodyguard”. What a great feat of communication!

Lima beans have other elegant defence strategies, says Wilhelm Boland. Many produce toxins (cyanogenic glucosides) that kill predators eating their leaves. Immediately after an attack, they also produce nectar at the point of attachment between the stalk and leaf stem. Typically, nectar is formed only in flowers to attract pollinators, but this extra nectar attracts patrolling ants. They are excellent allies. Ants prey on many herbivores such as caterpillars, small beetles, and other insects. They are generalists and as a reward get nectar.

Thus, the plant has a large arsenal of defensive strategies. If one strategy fails, she uses another. “Her secret recipe is variety,” says Wilhelm Boland, “and that is really necessary. You can put almost any herbivore predator on the lima bean and they will begin to eat away, except for lice; they do not love to feast on the lima bean. We do not know why.”

Besides warning fellow plants and attracting beneficial insects, what other situations demand that plants communicate? Naturally pollinators communicate via fragrances, says Wilhelm Boland. Using this language of fragrances, plants either promote or inhibit each other’s growth.

A well-known example is the sagebrush – a plant that grows virtually alone. The sagebrush uses a special fragrance to prevent other plants from growing nearby. The perfume industry also uses this well-studied fragrance, which is a mixture of methyl jasmonate, jasmone and short-chain unsaturated ketones. This fragrance conveys a specific meaning, depending on the circumstance. For instance, the scent may signal neighbouring plants to act defensively or warn neighbouring plants of a caterpillar invasion. In the case of the sagebrush, the fragrance stops other plants from growing nearby.

“The point is,” says Wilhelm Boland, “that the very same fragrance may play a completely different role in another plant, depending on the context.” After a pause he says: “It is complex, as it almost always is. And we are just at the beginning.” Again a pause, then he adds: “Plants structure their environment with the help of fragrances and communication.”

I look out of the window at a small forest. Each of these trees is restructuring her surroundings with fragrances and is, at the same time, being structured by others. Each tree becomes what she is – through communication. We could say: A plant is communication.

The researcher interrupts my musings. It is also interesting, he says, that wild plants generally have a larger vocabulary than cultivated plants. For example, wild cotton plants produce ten times the fragrances of cultivated cotton. Crops have been bred for centuries solely on the criteria of yield, but not on the communication abilities of the plant. These are often lost. “But maybe it makes sense for the ecosystem to resort to these methods of communication. Perhaps with our huge monoculture systems, we have committed a cardinal sin by making scent production entirely superfluous. It might be worthwhile to not allow the defence and breeding strategies of plants to fall by the wayside. Pesticide use could be reduced as a result.”