Articulation Morphology of Plants and Plant Evo-Devo: An empirical, dynamic, all-inclusive, and unifying approach based on open growth, ramification and articulation, inspired by the theory of anaphytes
by Rolf Sattler
This essay has been deleted because it has been published as
Sattler, R. Articulation morphology of plants and plant evo-devo: An open morphology - empirical, dynamic, all-inclusive, and unifying. Plants 2026, 15 (5), 730
https://doi.org/10.3390/plants15050730
https://www.mdpi.com/2223-7747/15/5/730
or
https://www.mdpi.com/2223-7747/15/5/730/pdf
Here, only coorections and updates to this essay will be published
Correction:
In the first line of the last paragraph of section #4, it should be ten approaches (instead of nine appraoches).
1st update:
Defense of plant morphology as a higher-level modern discipline – According to an anonymous reviewer of this paper, morphology that is not connected to molecular genetics is outdated and no longer at the forefront of modern plant biology – a view that is not uncommon. This view rests on the mistaken assumption that morphology is a finished discipline, completed in the past and now superseded by molecular research on development and evolution. However, as emphasized by Salmeri (2019), “plant morphology is not a conservative finished science, but, like other sciences, it is open to constant innovation involving both concepts and methods.” Recent innovations include continuum and process morphology (Rutishauser 2020), morpho evo-devo of the gynoecium (Sattler 2024), evo-devo morphology according to Regine Claβen-Bockhoff (2024; Sattler 2025), and the conceptual framework of articulation morphology (Sattler, 2026).
As plant morphology advances empirically and conceptually, it remains relevant to most other botanical disciplines (Sattler and Rutishauser, 1997). Today, it “still assumes a pivotal role in modern sciences, remaining fundamentally relevant to nearly all fields of plant biology, such as systematics, evolutionary biology, ecology, physiology, genetics, molecular biology, not to mention also agriculture, bioengineering, and forensic botany” (Salmeri, 2019). In evo-devo, morphology - as morpho evo-devo - is especially relevant to developmental genetics. Contrary to a widespread belief, morphology is not dependent on the results of developmental genetics. Although these results complement morphology and might be integrated with it, morphology constitutes a higher level of organization relative to the molecular level of developmental genetics, and this higher-level organization has emergent properties that cannot be reduced to, or predicted from, the lower level of molecules (e.g., Petrone-Mendoza et al. 2023, Ochoterena et al. 2019, Tomkins 2023). In this sense, morphology surpasses molecular genetics. Thus, rather than maintaining that morphology depends on molecular genetics and remains at the forefront of modern science only insofar as it is integrated with molecular genetics, we come to the opposite conclusion: molecular genetics, in as much as it uses morphological concepts, depends on the discipline of morphology that develops these concepts, which is an ongoing process. Unfortunately, many molecular geneticists in plant biology often do not seem to be aware of the most recent conceptual advances of plant morphology and therefore continue to rely on concepts of classical plant morphology that date back to Goethe’s Metamorphosis of Plants (1790) (see Sattler 2018) such as the root-stem-leaf model or the metameric model, which decomposes seed plants into phytomers.
For example, Venglat et al. (2025) present “a “universal” plant embryonic body plan from a developmental, molecular, and evolutionary perspective” in terms of the classical phytomer concept. This morphological concept cannot be derived from their molecular analysis. On the contrary, their molecular investigation is dependent on or influenced by this morphological concept that has been developed in the discipline of morphology, not in molecular biology. Are they aware of the shortcomings of this concept? The phytomer is a useful morphological concept, but it fragments the continuous stem into discrete units. To complement this concept, these authors might also have considered the leaf (phyllome) concept of the root-stem-leaf model, which recognizes the continuity of the stem but, in turn, fragments the stem-leaf continuum. Other conceptual models of the shoot (see Rutishauser and Sattler, 1985; Claβen-Bockhoff 2024, pp.488/9) lead to still other fragmentations. Thus, fragmentation is a problem when molecular geneticists rely uncritically on concepts of classical mainstream morphology - as they often do. In addition to fragmentation, another constraint of the phytomere concept is that it is mainly limited to seed plants. Telomic fossils and thalloid liverworts do not consist of phytomers. In contrast, the article concept of articulation morphology applies to all plants and acknowledges the continuity throughout the plant body because articles are continuous with one another, and their distinction is not based on non-existent boundaries or a morphological theory or model, but on the observable processes of ramification and articulation. It would be interesting and challenging to explore how the molecular genetics of the “universal” body plan proposed by Venglat et al. (2025) could move beyond the constraints of the classical phytomer concept through the use of the much more comprehensive article concept, and, more generally, how molecular genetics could benefit from this concept of articulation morphology.
Although molecular genetics depends on morphology as a higher-level discipline, morphology can be related to molecular genetics and other lower level disciplines, such as histology, the study of tissues. So far, these relationships have been explored mainly for the categories of classical morphology. The challenge now is to pursue them in terms of articles, which, as pointed out in Section #7 can lead to novel insights.
References
Claβen-Bockhoff, R. 2024. Die Pflanze: Morphologie, Entwicklung und Evolution von Vielfalt. Berlin: Springer Spektrum.
Ochoterena, H. et al. 2019. The search for common origin: Homology revisited. Syst. Biol. 68: 768-780.
https://doi.org/10.1093/sysbio/syz013
Petrone-Mendoza et al. 2023. Plant evo-devo. Trends Plant Sci. 28: 1257-1276.https://doi.org/10.1016/j.tplants.2023.06.007
Rutishauser, R. 2020. EvoDevo: Past and future of continuum and process morphology. Philosophies 5, 41. https://doi.org/10.3390/philosophies5040041
Rutishauser, R.; Sattler, R. 1985. Complementarity and heuristic value of contrasting models in structural botany. 1. General considerations. Bot. Jahrb. Syst. 107: 415-455.
Salmeri, C. 2019. Plant morphology: outdated or advanced discipline in modern plant sciences? Flora Medit. 29: 163-180. https://herbmedit.org/papers/8dd3f5fa-d587-4d2c-b6e7-39ad544993a3
Sattler, R. 2018. Philosophy of plant morphology. Elemente Naturwiss. 108: 55-79 (for an expanded version, see https://beyondwilber.ca/about/plant-morphology/philosophy-of-plant-morphology.html
Sattler, R. 2024. Morpho evo-devo of the gynoecium: heterotopy, redefinition of the carpel, and a topographic approach. Plants 13(5), 599. https://doi.org/10.3390/plants13050599
Sattler, R. 2025. Plant evo-devo morphology: An innovative new book by Regine Claβen-Bockhoff. Bot. Review 91: 437-441. https://doi.org/10.1017/s12229-025-09322-x
Sattler, R. 2026. Articulation morphology of plants and plant evo-devo: An open morphology – empirical, dynamic, all-inclusive, and unifying. Plants 15(5), 730. https://www.mdpi.com/2223-7747/15/5/730
Sattler, R.; Rutishauser, R. 1997. The fundamental relevance of plant morphology and morphogensis to plant research. Annals Bot. 80: 571-582.
Tomkins, M. 2023. Towards modelling emergence in plant systems. Quant. Plant Biol. 4:e6.
https://doi.org/10.1017/qpb.2023.6
Venglat, P. et al. 2025. Phytomers, collet and founder cells: a “universal” plant embryonic body plan from a developmental, molecular, and evolutionary perspective. Front. Plant Sci 16
https://doi.org/10.3389/fpls.2025.1521527
2nd update:
At the beginning of section #3, where I refer to Winther (2011) on the partitioning of the organism into body parts, the following reference should have been added:
Baum, D.A. 2019. Plant parts: Processes, structures, or functions? Gard. Bull. Singap. 71 (Suppl. 2): 225-256.
3rd update:
Because self-references were limited, the following paper could not be included, although it is highly relevant to the discussion of the carpel concept in Section 7:
Macdonald, A. D. and Sattler, R. 1973. Floral development of Myrica gale and the controversy over floral concepts. Can. J. Bot. 51: 1965-1976.
This paper documented in great detail that, during the development of the female flower, first two bracteoles are formed, followed by a ring primordium that gives rise to two or three styles, and an inner integument. The nucellus represents the continuation of the floral axis. In terms of articulation morphology, this means that two articles (the bracteoles) are formed first, followed by a ring primordium, an article that forms two or three articles (the styles), and another article (the inner integument), also arising from a ring primordium. This organization of the female “flower” of Myrica gale corresponds, to a great extent, to that of a gymnospermous ovule, such as those of the Gnetales, as was also pointed out in the floral concepts by Croizat and Meeuse. However, this resemblance has been obscured by the classical floral concept of mainstream morphology and has therefore been interpreted as the result of convergent evolution. Realizing how radically different floral concepts influence the description and interpretation of the “flower” of Myrica gale can lead to deeper insights into the enigma of floral morphology. Articulation morphology contributes an empirically based view that avoids preconceived notions of the flower.
4th update:
The following reference is also relevant to my paper:
Hay, A. 2019. Durianology, discovery, and saltation – the evolution of aroids. Gardens’ Bull. Singapore 71 (Suppl. 2): 257-313. https://www.nparks.gov.sg › ... · PDF file
Durianology, including the Durian Theory, refers to Corner’s holistic approach to the evolution of angiosperm form. Articulation morphology is also holistic in that it considers a plant as an articulated whole. To emphasize this wholeness, the subtitle of my paper could have been expanded to “An open morphology – empirical, dynamic, holistic, all-inclusive, and unifying.”
“An essential aspect of Corner’s approach was to consider plants as integrated systems – integrated not only within themselves but within their ecosystems – systems within systems” (ibid.). Articulation morphology emphasizes integration within plants. Because articles are continuous with one another, plants can be understood as internally integrated systems. The influence of an article on subsequent articles could be explored. Corner pointed out how the size of the stem influences leaf morphology.
Integration of plants within the ecosystem lies beyond
the scope of articulation morphology as a
strictly morphological approach. Nevertheless,
incorporating this dimension would enlarge the
scope of articulation morphology and contribute to a
more comprehensive understanding of plant evolution.
It would lead from evo-devo to eco-evo-devo (Tauber,
A.I. 2010. Reframing developmental biology…
Perspect. Bio. Med. 53: 257-270).
Integrating the environment of plants led Corner in his Durian Theory to a different view of angiosperm evolution according to which pachycaul trees with thick stems, compound leaves, and large fleshy fruits with arillate seeds – such as the durian – represented the ancestral condition of angiosperms. Jacobs (1976, cited in Hay’s article) hailed Corner’s Durian theory, including his principle of the transference of function, as “the most revolutionary contribution to botany of [the 20th] century.”
5th update:
Regine Claβen-Bockhoff (pers. comm.) noted that canalization, positioning, synorganization, and correlation were not included in articulation morphology. Indeed, they were not mentioned explicitly. However, they are compatible with or implied in articulation morphology and can be made explicit as follows:
1. Articles are defined in terms of process combinations, and canalization is inherent in these process combinations. As certain process combinations are constrained, they are canalized. An example is phyllotaxis, in which the divergence angle is constrained to a great extent by the Fibonacci series. As noted in my paper, phyllotaxis also applies to articles, although in a wider sense. The types of classical morphology – root, stem, and leaf - could also be seen as canalization and the misfits as decanalization. I should have quoted the paper by Mabberley, D. J. and Hay, A. 1994. Homoeosis, canalization, decanalization,’characters’ and angiosperm origins. Edinburgh J. Bot. 51: 117-126. These authors presented many examples of canalization and decanalization. I did not mention homeosis explicitly, but it too is implied or compatible with articulation morphology.
2. Positioning is implied in the origin of ramification such as lateral or axillary ramification.
3. Synorganization occurs through processes such as interprimordial and zonal growth, to which I referred in my paper. An example of synorganization is the gynostemium of orchids that is formed through zonal growth underneath the developing androecium and gynoecium, that is, the articles of these areas.
4. Correlations can be seen in a comparison of process combinations.
6th update:
Instead of implying that all plants exhibit open growth, I should have written that most plants show open growth. Exceptions occur. For example, Rafflesia displays a closed organization: the embryo does not develop an apical meristem; instead, it forms a protocorm from which organs arise though internal cleavage, and subsequently no more organs are added (Ng FSP. 2025. The reproductive biology of Rafflesiaceae. J. Tropical Forest Sci 37(2): 131-139. https://doi.org/10.26525/jtfs2025.37.2.131).
