Milieu

Scientific accounts of plant perception, behavior, and communication have provided us with dizzying arrays of the various means and materials through which plants react and respond to the worlds around them. Light, sound, chemical signals, physical vibrations—regardless of the mechanism, the picture of sensation that emerges in these accounts is a semiotic universe of multimodal signs available for the plant’s selective and reactive processing. In this model, the surroundings of organisms are sets of informational cues ready to be read and reacted to, and those responses are in turn incorporated into the shared text of the physical environment. Travis Brisini, following Eduardo Kohn, characterizes this process as biosemiotic exchange, where “life itself reflects the ‘aboutness’ of intentionality, insofar as the forms, matter, lifestyles, and continuation of living organisms are iconic and indexical representations of (‘about’) the world.”^[1]

Provisionally accepting this account of biosemiotic environments as reflecting the “aboutness” and intentionality of their organisms invites us to consider plant perception alongside the notion of milieu as it has been theorized by Georges Canguilhem. For Canguilhem, the living being’s behavioral milieu represents a set of stimuli that are not only present in an environment but “must also be noticed” by the organism in a manner that “presupposes an orientation of its interest.” As he puts it, “the stimulus does not proceed from the object, but from this interest.”^[2]It is necessary for a living being to organize its milieu by way of the values and significations it brings to these stimuli in order to act upon them, as opposed to navigating it via a matrix of meaning that is given from outside. However, we should not take this to imply in contrast that the living being is independent of its milieu and creates it as a purely subjective act. The organism and milieu form an “indivisible totality”^[3]whereby the stimuli of the milieu must respond to the interests of the organism but nevertheless provoke changes in its activity and orientation. A living being’s milieu neither precedes nor is determined by it in a single operation but rather exists as a unique and ongoing complementarity between the organism and its surroundings.^[4] For plants, whose activities are often difficult to distinguish from their own morphological self-transformations, the intimate mediation of self and environment afforded by a notion such as milieu neatly captures their mode of sensing their worlds and bringing them meaning.

However, when we take a closer look at the typical cases addressed by studies of plant communication in behavioral ecology or evolutionary biology, where plant behavior is conditioned by received environmental signals, these potential signs and the environment itself are in fact taken to precede the activity of the plant. Though these exchanges may center on the plant as a site for receiving and redirecting environmental signals, it is often as a mechanical or even empty center, insofar as the plant does not participate in these relays or seek out these inputs as more than a physical being or bundle of discrete sense organs. That is to say, the plant in this view would not have a milieu, only an external environment that fully determines its behavior in the last analysis.

If anything, the model of a universal system of informational cues present in physical signals, to which living beings would respond by pure reflex, comes much closer to an originary notion of milieu as a mechanistic concept. Against later associations with a vitalist or organicist holism, the mechanistic milieu dissolves a being’s activity into a totally decentered relay of physical exchanges. In this mechanical connotation, the milieu “becomes a universal instrument of the dissolution of individualized organic synthesis in the anonymity of elements and universal movements.” This leads to a position where, taking up Descartes’s formulation of animal behavior, Canguilhem identifies how this model leads ultimately to Descartes’s formulation of animal behavior, who had similarly posed that “It is nature that acts in them through the medium of their organs.”^[5] This mechanistic formulation was most systematically employed in the biological context by Auguste Comte, for whom the milieu was like a function that determined the traits of an organism as a set of variables: “weight, air and water pressure, movement, heat, electricity, and chemical elements, all factors capable of being studied experimentally and measured quantitatively.”^[6]

If this set of properties seems to echo the familiar lists of physical stimuli that plants may properly sense, it is not least because contemporary evolutionary and behavioral ecology seem to share something of Comte’s functionalism. An organism’s behaviors and their adaptive purposes must be experimentally identified and theoretically rationalized in terms of discrete functional responses to measurable environmental traits. In a critique of the then more controversial speculations about the bioacoustic activities of plants responding to sound, Bailey et al. define three criteria that plant audition would need to satisfy for their field: “To convincingly demonstrate that plant [acoustic] communication occurs as it is defined in the behavioral ecology literature, studies must show that (1) plants produce and respond to sound, (2) both traits provide an adaptive benefit, and (3) they have been historically selected for their communicative functions.”^[7]

The latter two requirements are of note insofar as they simultaneously preclude communicative behaviors developed on an individual or situational basis and instead acknowledge only those developed at a species level through processes of natural selection. For its sensory capacities to be recognized, the living being cannot be seen to alter its environment in a historico-material sense nor establish and modify its relation with its milieu in terms of the meanings and significations that the organism must itself help to produce. In other words, the ongoing individuation of the living being through which both it and its milieu are mutually determined is precluded by the parameters set up for identifying plant sensation and communication on purely evolutionary grounds, which instead render the organism “an intersection of influences.”^[8] All that remains is an abstract species-individual with a fixed environment decomposed into semiotic cues that connect specific physical supports (light, sound, chemicals) with already-established functional properties (responses by the organism).

This conceptual model is paired with the first requirement—the need to artificially isolate individual sensory capacities in the experimental scene—which requires that the subject’s behaviors be predictively identified and empirically isolated. Not only is the living individual in itself excluded from the process of spontaneously developing its conduct in conjunction with the development of its associated milieu, ascribing that process instead to a species-level adaption conducted within a fixed environment, but the experimental conditions themselves also exclude creative vital activity. As Canguilhem notes, “to study a living thing under experimentally constructed conditions is to create a milieu for it, to impose a milieu upon it. In fact, it is a fundamental characteristic of the living thing that it makes its own milieu; it builds one for itself.”^[9] In contrast, the conditions of experimentation require establishing an “abnormal” and “pathological” external milieu for the living being, which prompts specific and predictable behaviors from it by shifting it out of a state where it is governed by its own norms of living.

These disciplinary strictures manifest quite clearly in a notable experiment by Gagliano et al.,^[10] demonstrating how pea plants react to acoustic signals by directing their roots towards the recorded sound of water in dry soil. An important caveat to this result was that the plant’s roots tended to grow away from the electronic speaker in the absence of any additional factor on the control side of the trial. The authors’ hypothesized explanation—that the seedlings sensed the magnetic output of the sound equipment as an environmental condition to be avoided—is taken to show the pea plants “have the ability of ‘parsing’ their sensory world into its components of different types and hence, resolve the influx of information by prioritizing cues that support the overall most beneficial growth decision.”^[11] A paired speaker playing a silent signal was ultimately necessary on the control side of the experiment to isolate the purely acoustic effects determining root growth behavior. Even when the plant brings its own unanticipated modes of behavior into the artificial experimental scene, the disciplinary terms of the experiment required that this be decomposed into an even more stratified set of functional responses to extant environmental cues.

Revisiting this result from the perspective of organism/milieu rather than species/environment would encourage us to ask other questions. What would it take to allow this unexpected initial response to remain indicative of the pea plant’s potential to develop novel behaviors in relation to varied environmental stimuli according to its own orientations of interest? Are there experimental procedures that could show the organism establishing itself together with its milieu from the basis of internal norms, rather than imposing abnormal states as disturbances? Instead of dividing their perception into distinct sensory channels that can be neatly weighed against one another, how could we address the pea plants’ audition as something synesthetically integral of these acoustic and electromagnetic factors? These are inquiries that these authors and their results would likely encourage, but the parameters of their field make them difficult to directly address.

Moreover, a reaction such as the pea plant’s movement away from the electronic speaker’s magnetic signal prompts us to consider forms of perception and behavior without immediately obvious correlates present in the organism’s “natural” environment. A conventional evolutionary explanation would require a fixed aspect of this environmental trait or signal type to which the plant has been adapted via functions encoded into the bodily capacities of the abstract species-being. But through milieu we could instead reread this response in arguably more intuitive terms of invention. Might we not then say that an organism develops novel responses to novel situations, a process through which it generates its relational meanings with its world rather than only ever inheriting them?

            This recasting of environmental perception and reflexive behavior—so often positioned as the anchor for contemporary discourses of plant intelligence—into the problematics of milieu also forces us further to ask new questions of the kind of intelligence at stake here. Namely, we might begin to loosen it from the image of a purely subjective consciousness that reads the environment and directs the body without being present in either. If the organism’s mode of life is understood via the simultaneous and mutual modification of the milieu and the invention of new structures—the mediation between which is the organism’s significations—then we might introduce one new term to speak to this mediation: “technics.” Rather than the Darwins’ classic root-tip-as-brain analogy, which today seems to conjure up an impossible aim to center intelligence in a site of regulatory control, we could consider the root tip as tool, so long as we do not divest the tool of its role as a bearer of operative intelligence. As Canguilhem has it, “A living thing is not a machine that responds by movement to stimuli, it is a machinist who responds to signals by operations.”^[12] A new register opens up within which to think about the adaptive potentials of plant life and the histories of their practices, other than that which can be read off their genetic archives. The goal of this reframing is not to shift the agency of change back to the organism alone as an all-powerful intentional agent acting upon a passive environment. Rather, we might recognize the degree to which its very living expresses a creativity, inventing provisional solutions resonant with the potentiality of its environment, without elevating the latter into an overdetermining principle in turn. Returning the plant to the richer context of its milieu gives us new means to think through the relations of natural, cultural, and technical history and (vegetal) life’s proper role within their mesh.

 
Notes

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[1] Travis Brisini, “Phytomorphizing Performance: Plant Performance in an Expanded Field,” Text and Performance Quarterly 39, no. 1 (2019): 14.

[2] Georges Canguilhem, “The Living and Its Milieu,” trans. John Savage, Grey Room 3 (Spring 2001): 19.

[3] Canguilhem, “The Living and Its Milieu,” 24.

[4] This point is further emphasized in Gilbert Simondon’s later treatment of the concept: “The living being resolves problems, not just by adapting, i.e., by modifying its relation to the milieu [ . . . ] but by modifying itself, by inventing new internal structures, and by completely introducing itself into the axiomatic of vital problems.” In other words, the system of interests and values that the organism brings to structure its milieu is itself subject to transformation. See Gilbert Simondon, Individuation in Light of Notions of Form and Information, trans. Taylor Adkins (University of Minnesota Press, 2020), 7.

[5] Canguilhem, “The Living and Its Milieu,” 11–12.

[6] Canguilhem, “The Living and Its Milieu,” 10–11.

[7] Nathan W. Bailey et al., “Green Symphonies or Wind in the Willows? Testing Acoustic Communication in Plants,” Behavioral Ecology 24, no. 4 (2013): 798.

[8] Canguilhem, “The Living and Its Milieu,” 27.

[9] Canguilhem, “The Living and Its Milieu,” 19 (emphasis added).

[10] Monica Gagliano et al., “Tuned In: Plant Roots Use Sound to Locate Water,” Oceologica 184 (2017): 151–160.

[11] Gagliano et al., “Tuned In,” 158.

[12] Canguilhem, “The Living and Its Milieu,” 19.