Continuum Morphology and Process Morphology
deals with plant form, including its development and
evolution. It can be defined in a narrow sense as referring
only to external form, in contrast to anatomy that refers to
internal form. But plant morphology can also be defined in a
wide sense that includes both internal and external form at
all levels of organization from the molecular and cellular
level to the organismal level (Sattler, R. (ed.) 1978.
Theoretical Plant Morphology, Introduction).
Since molecular genetics has become fashionable, plant morphology has been increasingly neglected. Nonetheless, plant morphology remains fundamentally relevant to nearly all fields of plant biology such as molecular genetics, physiology, ecology, evolutionary biology and systematics. In these fields morphological concepts and/or theories are used or implied. Therefore, to some extent these fields are based on or reflect morphology (Sattler and Rutishauser 1997).
Contrary to a widespread misconception, plant morphology is not a finished science, but, like any science, open to constant innovation. Such innovation may concern details or concepts, theories, and even the disciplinary matrix (or paradigm). My contributions to plant morphology have been empirical and theoretical, involving a revision of some of the most basic assumptions and tenets in the disciplinary matrix of plant morphology (see also Yin-Yang and Dao (Tao)).
With many undergraduate and graduate students, technicians, postdoctoral fellows, research associates, and colleagues I carried out research in plant morphology for nearly forty years in the second half of the 20th century (see my Publications). One major focus of this research has been the dynamic form continuum in plants, especially flowering plants. A review of many aspects of this research can be found in my book chapter entitled “Homology, homeosis and process morphology in plants” in B.K. Hall (ed). 1994. Homology: The hierarchical basis of comparative biology. Academic Press, pp. 423-475. What follows is a brief summary of this work with some references that can be found in the list of my publications.
Mainstream plant morphology (also called classical plant morphology) emphasizes fragmentation and categorization. Thus, plants are conceptually fragmented into organ systems such as the shoot and root system, organs such as root, stem (caulome), leaf (phyllome), and outgrowths of these organs such as hairs (trichomes). Then the whole diversity of plant form such as that of flowering plants is reduced to categories of these fragments. Hence, every organ that is encountered in flowering plants must be either a root, or a stem, or a leaf, or homologous to any one of them.
Continuum Morphology - Although the fragmenting approach of mainstream morphology works to some extent, it tends to obscure the continuum of plant form. When we observe any one particular plant such as a flowering plant, we cannot find a clear-cut boundary between the root and the stem or the stem and the leaves. Furthermore, we cannot find a clear-cut boundary between the soil and the root or the leaves and the air. A close microscopic inspection reveals what has been called the Soil-Plant-Air Continuum (SPAC). Since animals and humans breathe in the air of this continuum, they are also included in it. With regard to various energies, this continuum extends into ecosystems, Gaia, and the whole universe. Thus, plant morphology and plant biology, although they may seem narrow fields, can become universal.
In spite of the continuum within plants, in textbooks and many research publications it is stated explicitly or assumed implicitly that plants such as flowering plants consist of roots, stems, and leaves. This gives the impression that roots, stems, and leaves actually exist as entities. However, since there are no clear-cut boundaries between these organs, we have to construct them through our delimitations. Although these delimitations have a limited validity, they do not constitute absolute discontinuities. Other delimitations that divide plants in different ways can also be made. For example, the leaf with a continuous part of the stem below it can be considered a unit of plant construction (Cusset, G. The conceptual bases of plant morphology. In Sattler, R. (ed.) 1982. Axioms and Principles of Plant Construction, pp.8 – 86 (also published in Vol. 31a of Acta Biotheoretica); Rutishauser and Sattler 1985*).
Units that result from different delimitations complement each other (Rutishauser and Sattler 1985). They illuminate different complementary aspects of plant construction and thus, together, provide a more comprehensive picture and understanding than any one single set of units such as the common root, stem and leaf units (for the concept of complementarity see chapter 6 of Wilber’s AQAL Map and Beyond, and my post Perspectivism and Complementarity: AQAL, the Big Tube, and the Dynamic Mandala).
When we compare organs of different plants, we find that although many of them can be grouped into categories such as root, stem (caulome) and leaf (phyllome), there are also intermediates between these categories. Thus, we find a structural continuum not only within plants but also between organ categories. This continuum even reaches beyond the organ level to include higher and lower levels of the structural hierarchy, thus leading to a new model of the shoot (Sattler 1971, 1974), referred to as the pyramid model of the shoot by Anthony and Sattler (1990). According to this model, the typical shoot occupies the top corner of the pyramid and the typical stem (caulome), leaf (phyllome), and hair (trichome) the three bottom corners of the tetrahedral pyramid. Intermediate structures occur in the space between the four poles of the tetrahedron (see Sattler. 1986. Biophilosophy, p. 105). Using principal component analysis, we demonstrated a continuum between roots, shoots, stems, leaves, and hairs (Sattler and Jeune, 1992).
Nonetheless, as long as we consider only structures that fit the structural categories, either/or thinking of our common Aristotelian logic is applicable. Thus, a structure belongs either to category A or B, an organ is either a stem (caulome), or a leaf (phyllome). However, if we consider the whole structural continuum, continuum or fuzzy logic is required because for intermediate structures it makes no longer sense to ask whether they are essentially A or B; they are neither A nor B; they represent partially A and B. In fuzzy logic we express to what degree they represent A and B. For example, the stamens of Commandra umbellata (that in mainstream plant morphology are interpreted as phyllomes, that is, leaf homologues), according to principal component analysis turn out as 51% phyllomes and 49% caulomes (stem homologues) (Sattler and Jeune 1992, Appendix 5, p. 261). (For a general discussion of fuzzy logic see Chapter 2 of Wilber’s AQAL Map and Beyond. For philosophical issues of plant morphology see Chapter 5 of my Biophilosophy book (1986) and my article “Some comments on the morphological, scientific, philosophical and spiritual significance of Agnes Arber’s life and work,” published in the Annals of Botany 88: 1215-1217, 2001).
The existence of intermediate structures has often been overlooked or denied because of excessive and overriding weighting of the position criterion. According to this criterion, structures are considered homologous, if they occupy the same relative position within the plant. Thus, what occurs in the axil of a leaf is considered a shoot, and what subtends a shoot is interpreted as a leaf. However, a simple thought experiment shows that this kind of reasoning can lead to absurd conclusions: for example, if we placed a leaf in the axil of a leaf, it would have to be homologized with a shoot. Obviously, this would not be a case of homology, but only homotopy (same position). Similarly, intermediate structures that we have found to occur in the axil of leaves are not essentially shoots, nor are they derived from shoots only; they are derived from the organs whose traits they share. For example, if they combine leaf and stem traits, they are derived from both leaves and stems: they represent hybrid structures or mosaics (Sattler, R. 1988. Homeosis in plants).
We have much evidence that not only the quality but also the relative position of structures may change, which means that one structure can be totally or partially replaced by another structure that may or may not be homologous. This phenomenon is called homeosis. Examples of total homeosis: the replacement of a stamen by a petal, or an axillary shoot by a leaf (Sattler 1988; Lehmann and Sattler 1993). Examples of partial homeosis: certain compound leaves that show a combination of leaf and shoot features (Sattler and Rutishauser 1992; Lacroix and Sattler 1994; Rutishauser and Sattler 1997; Rutishauser and Isler 2001) and therefore can be considered partially leaves and shoots as Agnes Arber has pointed out long ago in her Philosophy of Plant Form (1950) whose nearly 50th anniversary was celebrated in a symposium at the International Botanical Congress in 1999. In this symposium, Rutishauser and Isler (2001) contrasted Fuzzy Arberian Morphology (FAM) with the more restricted Classical Morphology (CLAM). Serge Meyen's work also went far beyond the limitations of classical morphology (see, e.g., Meyen, S.V. 1987. Fundamentals of Palaeobotany. London: Chapman & Hall). Like Arber's work, the contributions of Meyen (that focus on evolutionary plant morphology) have not received the attention they deserve. However, my own work has been much inspired by that of Serge Meyen (whom I once met in Moscow at the International Botanical Congress), Agnes Arber (whom I never met), and many others.
In Fuzzy Arberian Morphology or continuum morphology the concept of homology becomes also fuzzy. The question then is not whether an intermediate structure is homologous with A or B, but to what degree it appears homologous with A and B (Sattler 1966; Sattler 1884. Homology - a continuing challenge; Sattler 1994. Homology, homeosis and process morphology in plants). However, for structures that fit the categories, the common homology concept based on either/or logic seems still applicable.
The claims of continuum morphology have been supported by many detailed empirical investigations of shoot, leaf, and flower development in a great diversity of flowering plants (see my publications and those of other authors such as Rutishauser and Isler 2001). The complexity of developmental patterns that we presented in my book Organogensis of Flowers (1973) can also be understood in terms of continuum morphology (see also Flowers and Mandalas)
Investigations in molecular genetics have provided some support for continuum morphology. For example, it has been shown that certain compound leaves combine gene activity that is typical for shoot and leaf development (see below). Therefore, these compound leaves are not only morphological but also genetic mosaics, that is, intermediates between leaves and shoots as postulated by Agnes Arber’s partial-shoot theory of the leaf (Sattler and Rutishausr 1992; Rutishauser and Sattler 1997; Rutishauser and Isler 2001).
Process Morphology (Dynamic Morphology) - It can be useful to make a distinction between structure and process: for example, between the structure of a leaf and the processes that occur within the leaf. However, upon close inspection, we can see that the structure of the leaf changes and therefore can be seen as a process. Since it changes very slowly, this process is not easily noticeable, especially in later developmental stages as the leaf approaches maturity. But the leaf, like other structures, is never completely static. It always undergoes a process of growth and/or decay, differentiation and/or dedifferention. Within these four basic morphogenetic processes, subprocesses can be distinguished such as branching or symmetrisation. A whole structure such as a leaf can then be seen as a combination of processes, and the diversity of plant form can be understood as a diversity of process combinations (Sattler 1988. A dynamic multidimensional approach to floral morphology; Sattler 1990. Towards a more dynamic plant morphology; Sattler 1992. Process morphology: structural dynamics in development and evolution; Sattler 1993. Why do we need a more dynamic study of morphogenesis?; Sattler and Rutishauser 1990. Structural and dynamic descriptions of the development of Utricularia foliosa and U. australis). Many of the process combinations correspond to the typical organ categories. However, since there are intermediates that do not fit the categories, a continuum of process combination occurs (Jeune and Sattler 1992). The result: the dynamic form continuum of plants that I referred to above.
I called this dynamic approach to the study of plant form process morphology or dynamic morphology (Sattler 1990). And I applied it not only to plant development but also to the evolution of plants (Sattler 1998. On the origin of symmetry, branching and phyllotaxis in land plants).
Most of my publications, including my papers on fusion and continuity (Sattler 1978) and a new approach to gynoecial morphology (Sattler 1974) deal with processes, but, like almost all research in developmental and evolutionary plant biology, still imply a structure/process dichotomy.
One reason, maybe the main reason, why we imply so easily a structure/process dualism resides in the structure of our language. Most languages, including the English language, have a noun-verb or subject-verb-object structure in which nouns refer to things such as leaves and verbs to processes such as the processes of leaves (Sattler 1993. Why do we need a more dynamic study of morphogenesis?) If we could devise a language that is based on verbs only, we would have a pure process language that would no longer imply a structure/process dualism. Then we could easily recognize that what we call a leaf constitutes leafing, only activity.
In his Biological Principles (1967, p. 330), J.H. Woodger characterized the aim of process morphology very succinctly in very general terms when he wrote: "what is required is an enlargement of our concept of 'structure' so as to include and recognize that in the living organism it is not merely a question of spatial structure with an 'activity' as something over it, but that the concrete organism is a spatio-tempotal structure and that this spatio-temporal structure is the activity itself." In other words: a structure is not seen as having processes, a structure is seen as process(es). Hence, no structure/process dualism. Nonetheless, the structure/process dualism remains a useful perspective on biological phenomena, but its transcendence through process morphology reveals the dynamics of organic form more completely than the structure/process dualism inherent in mainstream biology.
Outlook - Although continuum and process morphology have not yet become mainstream because they are too different from deeply ingrained modes of thinking in our culture and science, they remain an active area of research in the 21st century. Denis Barabé, Bernard Jeune, Christian Lacroix, Rolf Rutishauser, and others continue research on the dynamic continuum of plant form. Furthermore, the dynamic continuum is validated by investigations in molecular genetics. For example, Hirayama et al (2007) showed that the phylloclade in Ruscus aculeatus "is not homologous to either the shoot or the leaf, but that it has a double organ identity," which means that it combines shoot and leaf processes (as has been documented on purely morphological grounds by Cooney-Sovetts and Sattler over twenty years ago). Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties." (Some morphologists, including myself, reached this conclusion long ago by purely morphological
investigations (see Rutishauser and Isler 2001). Finally, continuum and process morphology also play a role in plant evo-devo (evolutionary developmental biology) (see, e.g., Vergara-Silva, F. 2003. Plants and the Conceptual Articulation of Evolutionary Developmental Biology. Biology and Philosophy 18: 249-284).
Plant Morphology and Philosophy - Many plant morphologists and other scientists believe that science operates independently of philosophy. But it has been shown that science and philosophy remain intertwined: science includes philosophical assumptions and receives input from philosophy. Journals such as Biology and Philosophy are devoted to the relation between biological science and philosophy.
One philosophical assumption in mainstream plant morphology (classical plant morphology) involves essentialism (Sattler 1977. Essentialism in plant morphology) or, if not essentialism, at least Aristotelean either/or logic, the belief that any organ of plants such as flowering plants must be either a root, a stem (caulome) or leaf (phyllome), which means that even if an organ does not clearly fit these categories, it belongs nonetheless to one or the other (Sattler, R. 1986. Biophilosophy). The insistence on either/or supposedly has been justified by the phylogenetic interpretation of homology. It is argued, for example, that even if a structure appears to be an intermediate between a stem and a leaf, it evolved from either one or the other. However, in a strict sense, structures do not evolve from each other, that is, there is not direct phylogenetic connection between structures (Sattler 1984. Homology - a continuing challenge, p. 386). The phylogenetic connection or lineage is between organisms or populations. As has been known for a long time and as it is emphasized in evolutionary developmental biology, the development of organisms may change during evolution in such a way that elements of different developmental pathways may be combined. For example, it has been shown that certain compound leaves combine leaf and shoot processes, including genes that are associated with these processes (see, e.g., Rutishauser and Isler, 2001). Therefore, these compound leaves can be seen as partially homologous with leaves and shoots. The insistence in mainstream plant morphology that they are essentially leaves obscures their partial homology.
Most philosophers of science and biologists deny that essentialism still plays a role in mainstream thinking. However, listening to colleagues I have heard again and again expressions such as "but essentially it is this." Similar expressions one can often hear in everyday life, which to me indicates that essentialism is still deeply rooted in our culture.
Continuum morphology also freed itself from the constraints of Aristotelian either/or logic that is still taken for granted to a great extent in science and society. The logic of continuum morphology is fuzzy logic, or at least a more-or-less logic instead of or in addition to either/or logic.
Process morphology has incorporated ideas of process philosophy and contextualism. According to process philosophy, reality is seen as dynamic as in Buddhism that emphasizes impermanence. Contextualism also implies change: events are placed into the context of other events that may reach universal dimensions. For example, events (processes) that constitute a leaf (leafing), are intertwined with solar and cosmic radiation. Thus, the leaf (leafing) reaches cosmic dimensions. Since the integration is not limited to physical events but includes also subtle and very subtle events, it reaches even kosmic dimensions - kosmic, in contrast to cosmic, comprises matter, mind, and spirit (see the Prologue of Wilber's AQAL Map and Beyond). Because of the emphasis on integration, contextualism tends towards organicism and holism (Sattler, R. 1986. Biophiolosophy. Analytic and Holistic Perspectives, p. 245) (see also Ways of Thinking in my book ms Healing Thinking and Being).
The Importance of Questions - In a sense, questions seem more important or more fundamental than answers because the questions we ask determine to a great extent the kind of answers we obtain. If we ask an either/or question as it is typical for mainstream plant morphology and much thinking in science and society, the answer, if any, is in terms of a category. For typical structures, this kind of question seems appropriate. However, if we ask an either/or question for an intermediate structure, we cannot find a satisfactory answer because the question seems inappropriate in this particular situation. Therefore, before asking a question, one has to examine whether it appears appropriate.
Inappropriate questions have been called pseudo-questions because we cannot obtain satisfactory answers to these questions. Such questions obstruct progress. Recognizing pseudo-questions and posing new meaningful questions has led to great innovations in science and society.
Plant Morphology and Spirituality - A number of books on the relation between science and spirituality have been published, and symposia have been organized around this topic. In a symposium entitled "Divergence and Convergence of Sciences and Spirituality" that was dedicated to the Dalai Lama on the occasion of his 60th birthday on July 6, 1995, I discussed the relation of life science and spirituality (Sattler 1999. Divergence and convergence of sciences and spirituality: life science and spirituality). Already in 1976, I taught a summer course on "Modern Biology and Zen" at Naropa Institute in Boulder, Colorado. In this course, I explored no-thingness in biology, including plant morphology, and its relation to nothingness or emptiness in Buddhism, especially Zen. No-thingness means that there are no separate things but a continuum, undivided wholeness. As I pointed out above, a plant does not consists of things or entities such as organs. We create these things through our delimitations. Without these delimitations, there is no-thing. Also, the plant itself is no-thing, since it is fully integrated with its environment (see SPAC above).
Instead of no-thingness, we could refer to undivided wholeness, unity, or oneness, all of which play a central role in holistic science and spirituality, especially mysticism - hence a convergence of science and spirituality. Barbara McClintock, the 1983 Nobel Laureate in Physiology or Medicine, as a plant geneticist and mystic, exemplified this convergence when she wrote: "Basically, everything is one. There is no way in which you draw a line between things. What we [normally] do is to make these subdivisions, but they're not real. Our educational system is full of subdivisions that are artificial, that shouldn't be there" (quoted in Evelyn Fox Keller.1983. A Feeling for the Organism. The Life and Work of Barbara McClintock. Freeman, New York, p. 204).
There remains, however, also a difference between science and spirituality as mysticism. The scientist, especially the holistic scientist, has intellectual knowledge of nothingness, undivided wholeness, unity and oneness. The mystic experiences or is nothingness, undivided wholeness, unity, and oneness (Sattler 1977, 1999: see above).
Nothingness, undivided wholeness, unity and oneness in science as well as in process philosophy and process morphology refer to manifest reality that can be investigated through our senses and the thinking mind. However, beyond manifest reality - but not separate from it - we can find the unmanifest source, the unnamable. Since it cannot be named, one cannot say that it is dynamic or static, discontinuous or continuous, fragmented or whole. We cannot even say that it is both dynamic and static, discontinuous and continuous, fragmented and whole. It is beyond words and concepts, and therefore it appears mysterious... "The Tao that can be told is not the eternal Tao...The unnamable is the eternally real" (Tao Te Ching, translated by Stephen Mitchell. HarperPerennial, 1992)..
Most scientists, especially mechanistic mainstream scientists, including mainstream plant morphologists, shy away from or denigrate mystery. However, some of the greatest scientists recognize that beyond that which can be grasped by the intellect lies the unfathomable mystery that transcends science but can inspire scientists. For example, Albert Einstein, the great physicist, wrote: "The most beautiful thing we can experience is the mysterious. It is the source of all true art and science"(quoted by Ravi Ravindra. 2000. Science and the Sacred. The Theosophical Publishing House, Wheaton, IL,USA)
Plant Morphology in Relation to the Theme of my Website. - You might ask whether plant morphology relates to “Ken Wilber, the AQAL Map, Health and Laughter,” the title of my website. Yes, indeed it relates in many ways. Let me briefly mention the following:
1. Ken Wilber severely criticized the myth of the given, “the belief that reality is simply given to me…instead of a world that is con-structured in various ways before it ever reaches my empirical or phenomenal awareness” (Ken Wilber. 2006. Integral Spirituality, p. 176). We find an expression of this myth of the given in mainstream plant morphology where it is often taken for granted that plants such as flowering plants consist of roots, stem(s), and leaves. But as I have pointed out, these organs are constructed through our delimitations – they are not given by nature. As Ken Wilber and others, especially postmodern authors, have emphasized, our constructions reflect our culture. Since Aritotelian either/or logic consitutes still a fundamental part of our mainstream culture, it is reflected in mainstream plant morphology and its central concept, the concept of homology. However, for a long time, at least a few plant morphologists have gone beyond either/or thinking (see Cusset, G. The conceptual bases of plant morphology. In Sattler, R. (ed).1982. Axioms and Principles of Plant Construction, pp. 8-86; Rutishauser and Isler 2001). Unfortunately, their innovations have not been incorporated into mainstream plant morphology.
2. Ken Wilber’s AQAL map is hierarchical (holarchical) with regard to the basic levels (structure stages) of manifest reality. He states that organisms are composed of cells, which are composed of molecules, which are composed of atoms. According to a more refined version of this hierarchical view, organisms are composed of organ systems, composed of organs, composed of tissues, composed of cells, etc. Thus, plants such as flowering plants are composed of the root system and shoot, the former is composed of roots, the latter of stems and leaves (and their homologues). Furthermore, all organs may have trichomes (hairs), which are tissue outgrowths. Thus, we are dealing here with three levels of the hierarchy of plant construction: organ systems, organs, and tissues. As I pointed out above, we found a continuum between these three levels of the hierarchy, which means that the hierarchy collapses at these levels, since a hierarchy requires levels (Sattler and Jeune 1992; Jeune and Sattler 1992). I have shown that the hierarchy can also be collapsed at other levels (see Wilber’s AQAL Map and Beyond, Chapter 1). This does not mean that hierarchical thinking is completely useless, but it is limited and therefore needs to be complemented by other ways of thinking such as continuum thinking (fuzzy logic).
3. In Chinese medicine health means balance. This notion is applied to our physical, emotional, and spiritual health. It can also be applied to plant morphology. Recognizing only the root-stem-leaf delimitations of plants such as flowering plants and treating them as given appears one-sided and unbalanced. But recognizing complementary delimitations creates more balance and thus a healthier plant morphology. Furthermore, recognizing and applying healing ways of thinking (healing logic) can heal the wounds and conflicts that have been inflicted by an insistence on Aristotelian either/or logic, especially in cases of a continuum where it does not apply.
4. Plant morphologists who embrace the root-stem-leaf delimitations of plants such as flowering plants seem often dead serious, and sometimes even aggressive and outright nasty, in its defense. Unfortunately, such behavior is not restricted to plant morphology but occurs also in many other areas of science, philosophy, ideology, and religion. If we could go beyond the myth of the given and recognize the relativity of different views (which does not mean that they are necessarily equally valid; see, for example, Sattler 2009), we could inject lightness, humor and laughter into this exaggerated seriousness, which would be healing not only for individuals but also for the scientific community, society and the planet (see, for example, laughter yoga).
*For references without the title see under Refereed Papers in the list of my publications. For references with the title see under Book Chapters and Symposium Contributions in the same list.
Evolution of my Morphological Thinking Documented through
my Publications and Plant Evo-Devo (Evolutionary
Plant Morphology to Infinite Issues (including Ken Wilber
and Korzybski) and
Power and LImitations