Plant Sensing and Communication
by Richard Karban
University of Chicago Press, 2015
Cloth: 978-0-226-26467-7 | Paper: 978-0-226-26470-7 | Electronic: 978-0-226-26484-4
DOI: 10.7208/chicago/9780226264844.001.0001


The news that a flowering weed—mousear cress (Arabidopsis thaliana)—can sense the particular chewing noise of its most common caterpillar predator and adjust its chemical defenses in response led to headlines announcing the discovery of the first “hearing” plant. As plants lack central nervous systems (and, indeed, ears), the mechanisms behind this “hearing” are unquestionably very different from those of our own acoustic sense, but the misleading headlines point to an overlooked truth: plants do in fact perceive environmental cues and respond rapidly to them by changing their chemical, morphological, and behavioral traits.

In Plant Sensing and Communication, Richard Karban provides the first comprehensive overview of what is known about how plants perceive their environments, communicate those perceptions, and learn. Facing many of the same challenges as animals, plants have developed many similar capabilities: they sense light, chemicals, mechanical stimulation, temperature, electricity, and sound. Moreover, prior experiences have lasting impacts on sensitivity and response to cues; plants, in essence, have memory. Nor are their senses limited to the processes of an individual plant: plants eavesdrop on the cues and behaviors of neighbors and—for example, through flowers and fruits—exchange information with other types of organisms. Far from inanimate organisms limited by their stationary existence, plants, this book makes unquestionably clear, are in constant and lively discourse.


Richard Karban is professor of entomology and a member of the Center for Population Biology at the University of California, Davis. He is coauthor of Induced Responses to Herbivory, also published by the University of Chicago Press, and How to Do Ecology: A Concise Handbook.


“Karban seeks to argue that plants behave—that they sense their environment, detect and communicate with an array of different organisms, and respond to their sense of the environment and communication. He is very successful in this, demonstrating that plant sensing and communication is a vibrant area of current research with still plenty more to discover. Very unusual, with broad appeal, so timely and well written, this book will be essential reading for specialists and a landmark in the field. Plant Sensing and Communication is a fantastic book.”
— Graeme D. Ruxton, University of St Andrews, UK, coauthor of "Experimental Design for the Life Sciences" and "Plant-Animal Communication"

“Effective because it sweeps across so many aspects of plant biology, and ecology and evolutionary biology more generally, Plant Sensing and Communication is also very well written, easy to digest, and feels like an unrushed synthesis. Certain signature aspects of Karban’s clarity shine through in this book. For example, the dichotomous keys to, and categorization of, certain types of interactions are a hallmark of Karban’s ability to simplify and clarify, and these will be useful to readers for decades (even if they disagree). This book will be read widely and have a lasting impact.”
— Anurag Agrawal, Cornell University, coeditor of "Induced Plant Defenses Against Pathogens and Herbivores"

“Richard Karban gives an introduction to a secret world: the multiple ways via which plants obtain information on their environment. Plants identify microbes and animals with which they are in contact, distinguish friends from foes, perceive the presence and degree of attack of their plant neighbors. They successfully integrate all this information and respond with adequate behaviors to enhance their chances of survival end reproduction. Reports on talking trees and intelligent plant behavior make it regularly into the public press, but they frequently leave the impression that botanists humanize their study objects, perhaps to make them more attractive for the public. In Plant Sensing and Communication, Karban carefully avoids this pitfall and provides us with detailed descriptions of all the physiological mechanisms that enable plants to gain information on their environment, make optimal use of the resources available, and actively manipulate their biotic environment for their own benefits.”
— Martin Heil, Cinvestav Unidad Irapuato, Mexico

“Plants are smart, . . . but to notice we have to overcome our ingrained cultural biases. . . . Clearly, we will never play chess with a rose, nor ask the orchid on our windowsill for advice. But that is the point: humans are guilty of serious parochialism, of defining intelligence in terms of a nervous system and muscle-based speed that enables things to be done fast. . . . Plants . . . are highly responsive, attuned to gravity, grains of sand, sunlight, starlight, the footfalls of tiny insects, and to slow rhythms outside our range. They are subtle, aware, strategic beings whose lives involve an environmental sensitivity very distant from the simple flower and seed factories of popular imagination. . . . . Plant Sensing and Communication [is a] timely, highly accessible summar[y] of fast-developing fields. . . . [It] combine[s] a passion for plants and a desire to illustrate their largely unsung complexities with an appreciation of the burden of proof needed to persuade us of a world that contains chlorophyllic sentience.”
— Adrian Barnett, New Scientist

“Karban . . . largely avoids political melodrama, instead providing clear working definitions of some of the contentious vocabulary: communication, eavesdropping, learning and memory. His summaries of plants’ sensory abilities—such as the cues and signals that they use to adjust to the environment—retain an evolutionary perspective. And he branches out into areas such as mate choice, for example detailing how plants selectively breed with specific fathers represented in a mixed pollen load.”
— Ian T. Baldwin, Max Planck Institute for Chemical Ecology, Nature

“A wonderful book; not least because it is a celebration. A celebration of the exquisite sensory capabilities of plants, and an exploration of their capacity to communicate with other entities. How refreshing it is to live on a planet where our green neighbours have such extraordinary talents. And how thrilling is it that humans—if they try hard enough and aren’t blinded by notions of zoosupremacy—have the capacity to appreciate, explore, and understand that side of those resourceful organisms with whom we share the planet. Even if some humans still remain resolutely plant-blind, it is clear that plants themselves are anything but blind; they see their environment extremely clearly and with great acuity. Now, if only we could all see plants in the same way . . .”
— Nigel Chaffey, Bath Spa University, UK, Annals of Botany Blog: News and Views on Plant Science and Ecology

“Sensational headlines about plant communication have appeared in newspapers in recent years. In this work, however, Karban has written a basic outline of plant sensing and communication drawn from extensive research in botany, ecology, and agriculture. . . . Recommended.”
— J. Cummings, Washington State University, Choice



- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0001
[behavior, communication, cues, sensing]
Like animals, plants exhibit many complex behaviors. Plants lack central nervous systems so the sensory mechanisms responsible for these behaviors are quite different than those of animals although both share similar challenges. Plants are made up of repeated modular organs that can be added or shed far more easily than the specialized organs of animals, allowing plants to respond morphologically to their environments. Plant behavior is defined as a change that occurs rapidly and reversibly in response to a stimulus. Communication occurs when a receiver responds to a cue emitted by a sender. (pages 1 - 8)
This chapter is available at:

1.1 - Plants and animals are different but also similar

1.2 - Working definitions

1.3 - Plant sensing and communication—organization of this book

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0002
[light, phytochrome, receptors, sensing, sound, stimuli, touch]
Plants live in variable, heterogeneous environments and they have evolved the ability to sense and respond to spatial and temporal variation in light, chemicals, touch and gravity, temperature, sound, and electromagnetic forces. Phytochrome receptors sense the quality of light by responding to the ratio of red to far-red wavelengths allowing plants to detect shade cast by competitors. Chemical cues allow plants to recognize nutrient gradients as well as pathogens and herbivores. Plants use both dedicated receptors and diffuse feedback mechanisms to sense their environments. (pages 9 - 30)
This chapter is available at:

2.1 - Plants sense their environments

2.2 - Plants sense light

2.3 - Chemical sensing

2.4 - Mechanical sensing—touch

2.5 - Plant sensing of temperature, electricity, and sound

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0003
[acclimation, conditioning, learning, memory, priming, transgenerational memory]
Animals are believed to have learned when past experiences influence future responses. Similarly, plants can be considered to have learned when past events cause chemical changes that alter the sensitivity, speed, or effectiveness of plant sensing and responses. Prior experiences involving light, chemicals, resources, pathogens and herbivores have all been found to affect subsequent plant behaviors. Most examples of plant learning involve rapid and short-lived memory although these are sometimes more durable, lasting the entire life of the individual. Many recent studies also indicate transgenerational effects in which offspring phenotypes are influenced by both their genes as well as the experiences of their parents and earlier ancestors. (pages 31 - 44)
This chapter is available at:

3.1 - Do plants learn?

3.3 - Learning, memory, and perception of chemicals, resources, pathogens, and herbivores

3.4 - Learning, memory, and touch

3.5 - Learning, memory, and cold

3.5 - Transgenerational memory

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0004
[cues, eavesdropping, signals]
Animal behaviorists differentiate between cues, which cause a response in a receiver, and signals, which are cues that increase the expected fitness of the sender. Plant responses tend to have multiple elicitors and these cues often have redundant effects. Plants also emit cues and signals which are then available to other organisms that exploit plants. For example, animals respond primarily to visual and chemical cues to locate and use plant tissues. (pages 45 - 66)
This chapter is available at:

4.1 - The nature of cues and signals

4.2 - Plant competition—light and hormonal cues

4.3 - Cues used in plant defense

4.4 - Cues and signals emitted by plants that animals sense

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0005
[allocation, foraging, roots, self/non-self discrimination, shade avoidance, shoots]
Resources are available in patchy environments and plants sense and respond by placing shoots and roots in relatively rich patches. Plants forage for light and soil nutrients by differentially allocating semi-autonomous modules and thereby adjusting their morphologies. Responses to light quality and quantity often produce shade avoidance syndrome characterized by elongated internodes, fewer leaves, and earlier investment in reproduction. Shorter-term variation in light can result in physiological adjustments. Root topology is adjusted to exploit patchy soil nutrients. Plants recognize their own attached roots versus those of other individuals and avoid competing with themselves. Plants allocate internal resources so as to balance the needs of roots and shoots and they have some ability to coordinate allocation decisions. Many plants appear to prioritize allocation to acquire resources over defense. (pages 67 - 82)
This chapter is available at:

5.1 - General characteristics of plant responses

5.2 - Plants forage for resources

5.3 - Integrating resource needs

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0006
[cues, induced responses, indirect defenses, localized responses, reliability, risk, volatile communication]
Risk of herbivore attack is heterogeneous and plants use information to evaluate their current or future risk and to adjust their defensive phenotypes accordingly. These induced plant responses will only be effective if cues reliably predict future risk. Since plants are made up of semi-autonomous modules that often communicate incompletely, many induced responses to herbivory are localized and increase heterogeneity in plant defensive traits. Vascular communication among organs of individual plants is often poor and many plants rely on volatile cues to coordinate systemic induced responses. Plants also defend themselves indirectly by attracting the predators and parasites of their herbivores; they offer rewards such as food or shelter and, in some cases, information (cues) that these carnivores find valuable. (pages 83 - 108)
This chapter is available at:

6.1 - Induced responses as plant defenses

6.2 - Volatile signals and communication between ramets and individuals

6.3 - Indirect defenses against herbivores

6.4 - Visual communication between plants and herbivores

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0007
[fertilization, flower visitor, fruit, nectar, pollination, seed abortion, seed dispersal]
Plants are incapable of fertilization and seed dispersal without external agents and they provide these agents with rewards, including informative cues. Animals visit flowers to collect nectar and pollen and fertilize seeds only as a byproduct. Flowers advertise for visitors although not all visitors pollinate. Flowers sometimes increase rates of outcrossing by limiting visitation to a subset of visitors using physical means or specific cues. Female plants may influence fertilization of their ovules by manipulating cues and other resources as well as selectively aborting seeds fertilized by certain fathers. Plants often reward seed dispersers by providing nutritious fruits or seeds. Since seed and fruit feeders vary in the quality of their services, plants attempt to control seed and fruit dispersers. (pages 109 - 128)
This chapter is available at:

7.1 - Pollination and communication

7.2 - Seed dispersal and communication

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0008
[microbes, mycorrhizal fungi, nitrogen-fixing bacteria, pathogens, recognition]
Plants recognize and protect themselves against harmful pathogens but acquire mycorrhizal fungi and nitrogen-fixing bacteria. Plants attract or filter potential microbial colonists. They recognize highly conserved cues of microbial groups and then either attempt to destroy or facilitate those microbes. Mycorrhizal fungi absorb water and nutrients from the soil and plants provide them with carbohydrates in exchange for these resources. Colonization of plant roots by mycorrhizal is a highly orchestrated process involving mutual signaling. Many plants are limited by available nitrogen although they can acquire this resource from particular strains of bacteria. Some bacteria can fix atmospheric nitrogen and provide fixed N to plants in exchange for other resources. Leguminous plants offer specialized structures for the bacteria and these partners engage in an intricate dialogue of chemical signaling during colonization. Plants evaluate and reward more cooperative mycorrhizae and N-fixing bacteria at the expense of less profitable strains. (pages 129 - 138)
This chapter is available at:

8.1 - Microbes are critical for plant success

8.2 - Plants recognize pathogens

8.3 - Infested plants attract the microbial enemies of their attackers

8.4 - Plants communicate with mycorrhizal fungi

8.5 - Plants communicate with N-fixing bacteria

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0009
[adaptation, anthocyanins, fitness, heritability, phylogenetic analysis, pollination, rewardless flowers, shade avoidance responses, variation]
For a trait to be considered as an adaptation shaped by natural selection, it must have been variable, heritable, and increased the relative fitness of individuals that possessed it relative to other traits. Phylogenetic analyses can suggest the likely history of traits involved with plant sensing and communication. Three examples of sensing and communication are considered as adaptations. Anthocyanins provide visual cues that attract visitors to flowers and fruits. Anthocyanins are variable, heritable, and associated with increased plant fitness although it is not definitive that pollinators were the selective agents. Phytochrome receptors allow plants to sense their light environments and avoid being shaded. Plants that responded to light cues and assumed appropriate phenotypes had higher fitness than those that did not. Some deceptive flowers advertise to animal visitors but provide no actual rewards. Rewardless flowers attract visitors that cannot discriminate and such flowers may be associated with higher plant fitness. These examples indicate how difficult it is to evaluate how natural selection has shaped particular traits. (pages 139 - 162)
This chapter is available at:

9.1 - Plant senses and emission of cues—adaptive traits?

9.2 - Case studies of adaptations

- Richard Karban
DOI: 10.7208/chicago/9780226264844.003.0010
[agriculture, allocation, medicine]
It may be possible to manipulate the cues or the communication process to produce plant phenotypes or products that are useful in agriculture or medicine. We have attempted to manipulate resource acquisition and allocation, tolerance to abiotic stresses, induced responses to pathogens and herbivores, and the timing and effort allocated to reproduction. Many pharmaceutical drugs are natural products resulting from interactions between microbes and/or plants. By understanding and altering these interactions, we may improve our collection of useful medicines. (pages 163 - 180)
This chapter is available at:

10.1 - Manipulating the sensing and communication process

10.2 - Manipulating resource acquisition and allocation

10.3 - Manipulating tolerance to abiotic stress

10.4 - Manipulating resistance to pathogens

10.5 - Manipulating resistance to herbivores

10.6 - Manipulating reproductive timing and effort

10.7 - As a source of medicines

10.8 - Plant sensing in the future of mankind