Evolutionary developmental biology (evo-devo) is the study of developmental programs and patterns from an evolutionary perspective. It seeks to understand the various influences shaping the form and nature of life on the planet. Evo-devo arose as a separate branch of science rather recently. An early sign of this occurred in 1999.
Most of the synthesis in evo-devo has been in the field of animal evolution, one reason being the presence of model systems like Drosophila melanogaster, C. elegans, zebrafish and Xenopus laevis. However, since 1980, a wealth of information on plant morphology, coupled with modern molecular techniques has helped shed light on the conserved and unique developmental patterns in the plant kingdom also.Minelli, A. 2018. Plant Evolutionary Biology. The Evolvability of the Phenotype. New York: Cambridge University Press.
Historical perspective
Before 1900 Gérard Cusset provided a detailed in-depth analysis of the history of plant morphology, including plant development and evolution.Cusset G (1982). "The Conceptual Bases of Plant Morphology." In: Sattler R (1982). Axioms and Principles of Plant Construction. The Hague: Martinus Nijoff/ Dr W. Junk Publishers, pp. 8–86 (also published in Acta Biotheretica 31A) The origin of the term "morphology" is generally attributed to Johann Wolfgang von Goethe (1749–1832). He was of the opinion that there is an underlying fundamental organisation () in the diversity of flowering plants. In his book The Metamorphosis of Plants, he proposed that the enabled us to predict the forms of plants that had not yet been discovered. Goethe was the first to make the perceptive suggestion that flowers consist of modified leaves. But he also entertained different complementary interpretations.Cusset G (1982). "The Conceptual Bases of Plant Morphology." In: Sattler R (1982). Axioms and Principles of Plant Construction. The Hague: Martinus Nijoff/ Dr W. Junk Publishers, p.27 (also published in Acta Biotheretica 31A)(for an expanded version of this article see ) During the history of plant morphology, several contradictory concepts of the flower have been proposedMacdonald, A.D. and Sattler, R. 1973. Floral development of Myrica gale and the controversy over floral concepts. Can. J. Bot. 51:1965-1973.
In the middle centuries, several basic foundations of our current understanding of plant morphology were laid down. Nehemiah Grew, Marcello Malpighi, Robert Hooke, Antonie van Leeuwenhoek, Wilhelm von Nageli were just some of the people who helped build knowledge on plant morphology at various levels of organisation. It was the taxonomical classification of Carl Linnaeus in the eighteenth century though, that generated a firm base for the knowledge to stand on and expand.http://www.cas.muohio.edu/~meicenrd/ANATOMY/Ch0_History/history.html Plant Morphology: Timeline The introduction of the concept of Darwinism in contemporary scientific discourse also had had an effect on the thinking on plant forms and their evolution.
Wilhelm Hofmeister, one of the most brilliant botanists of his times, was the one to diverge away from the idealist way of pursuing botany. Over the course of his life, he brought an interdisciplinary outlook into botanical thinking. He came up with biophysical explanations on phenomena like phototaxis and geotaxis, and also discovered the alternation of generations in the plant life cycle.
1900 to the present
The past century witnessed a rapid progress in the study of plant anatomy. The focus shifted from the population level to more reductionist levels. While the first half of the century saw expansion in developmental knowledge at the tissue and the organ level, in the latter half, especially since the 1990s, there has also been a strong impetus on gaining molecular information.
Edward Charles Jeffrey was one of the early evo-devo researchers of the 20th century. He performed a comparative analyses of the vasculatures of living and fossil gymnosperms and came to the conclusion that the storage parenchyma has been derived from tracheids. His research focussed primarily on plant anatomy in the context of phylogeny. This tradition of evolutionary analyses of plant architectures was further advanced by Katherine Esau, best known for her book The Plant Anatomy. Her work focussed on the origin and development of various tissues in different plants. Working with Vernon Cheadle,Plant Science Bulletin she also explained the evolutionary specialization of the phloem tissue with respect to its function.
In 1959 Walter Zimmermann published a revised edition of .Zimmermann, W. 1959. Die Phylogenie der Pflanzen. Revised 2nd edition. Stuttgart: Gustav Fischer Verlag. This very comprehensive work, which has not been translated into English, has no equal in the literature. It presents plant evolution as the evolution of plant development (hologeny). In this sense it is plant evolutionary developmental biology (plant evo-devo). According to Zimmermann, diversity in plant evolution occurs though various developmental processes. Three very basic processes are heterochrony (changes in the timing of developmental processes), heterotopy (changes in the relative positioning of processes), and heteromorphy (changes in form processes).Sattler, R. and Rutishauser, R. (2023). Feature Paper: Fundamentals of plant morphology and plant evo-devo (evolutionary developmental biology). ' ' Plants ' ' 12(1): 118-131. https://doi.org/10.3390/plants12010118 In the meantime, by the beginning of the latter half of the 1900s, Arabidopsis thaliana had begun to be used in some developmental studies. The first collection of Arabidopsis thaliana mutants were made around 1945. TAIR: About Arabidopsis However it formally became established as a model organism only in 1998.
The recent spurt in information on various plant-related processes has largely been a result of the revolution in molecular biology. Powerful techniques like mutagenesis and complementation were made possible in Arabidopsis thaliana via generation of T-DNA containing mutant lines, recombinant plasmids, techniques like transposon tagging etc. Availability of complete physical and genetic maps,The Arabidopsis Information Resource RNAi vectors, and rapid transformation protocols are some of the technologies that have significantly altered the scope of the field. Recently, there has also been a massive increase in the genome and EST sequencesNCBI dbEST Statistics of various non-model species, which, coupled with the bioinformatics tools existing today, generate opportunities in the field of plant evo-devo research.
Despite this progress in molecular biology, morphology remains central to evo-devo because it provides a conceptual framework. Furthermore, as morpho evo-devo or evo-devo morphology, it is important because it deals with higher-level organization that cannot be reduced to the lower level of molecules. In this sense, morphology surpasses molecular evo-devo. Thus, Petrone-Mendoza et al. (2023) demonstrated that "plant morpho evo-devo provides data that genes could never furnish."Petrone-Mendoza et al. (2023) Plant morpho evo-devo. Trends Plant Sci. 28: 1257-1276. https://doi.org/10.1016/j.tplants.2023.06.007
Rolf Sattler discussed fundamental principles of plant morphologySattler, R. "Plant Morphology. Fundamental Issues".Sattler, R. "Philosophy of Plant Morphology" ' ' ' ' and its relation to evo-devo.Sattler, R (2024) Feature Paper: Morpho evo-devo of the gynoecium: heterotopy, redefinition of the carpel, and a topographic approach. ' ' Plants ' ' 13(5), 599.https://www.mdpi.com/2223-7747/13/5/599.Sattler, R. "Plant evo-devo and the morphological research by Rolf Sattler and collaboraters". Rolf Rutishauser surveyed the past and future of continuum and process morphology with regard to evo-devo. Two voluminous, richly illustrated volumes have become milestones for plant morphology and plant evo-devo in the 21st century: Kaplan, D. R, edited by Specht, C.D. (2022) Principles of Plant Morphology Kaplan, D. R., edited by Specht, C. D. 2022. Kaplan's Principles of Plant Morphology. New York: CRC Press.Sattler, R (2022) Kaplan's Principles of Plant Morphology: A Critical Review. Botanical Review 88: 257-270. https://doi.org/10.1007/s12229-022-09280-8 and Claβen-Bockhoff, R. (2024) Die Pflanze: Morphologie, Entwickung und Evolution von Vielfalt (The Plant: Morphology, Development and Evolution of Diversity)Classen-Bockhoff, R.2024. Die Pflanze: Morphologie, Entwicklung und Evolution von Vielfalt. Berlin: Springer Spektrum.Rolf Sattler (2025) Plant Evo-Devo Morphology: An Innovative New Book by Regine Claβen-Bockhoff. The Botanical Review, Dec. 8, 2025. https://doi.org/10.1007/s12229-025-09322-x Whereas Kaplan's work remained firmly within the framework of classical mainstream morphology, Claβen-Bockhoff introduced conceptual innovations that open up new avenues for evo-devo, especially morpho evo-devo. The most recent innovation is Articulation Morphology.Rolf Sattler (2026) Articulation morphology of plants and plant evo-devo: An open morphology - empirical, dynamic, all-inclusive, and unifying. Plants 13(5),599. https://www.mdpi.com/2223-7747/15/5/730 Articulation Morphology, grounded in the open growth of plants, focuses on ramification as the key principle of plant morphology. This principle entails articulation: the formation of articles, which may differentiate in many ways. Unlike organs, which are defined in terms of a morphological theory such as the root-stem-leaf model, articles, which have been almost completely overlooked, are directly observable, that is, they are factual and objective. As such, articulation morphology, based on articles, offers a common foundation for all morphologists, regardless of their theoretical preferences. While so far plant morphology has been largely centered around homology, articulation morphology shifts the focus to the transformation of ramification and articulation during development and evolution. This shift has far-reaching consequences for plant morphology and plant evo-devo.Rolf Sattler (2026) Articulation morphology of plants and plant evo-devo: An open morphology - empirical, dynamic, all-inclusive, and unifying. 15 (5), 730. https://www.mdpi.com/2223-7747/15/5/730 Furthermore, recognizing open growth as the most fundamental process of plant development that distinguishes plants from animals, entails the concept of the article as the most fundamental structural unit that applies to all plants, from algae to bryophytes to vascular plants, and encompasses the continuum between morphological categories and levels of organization, from organ systems to organs, parts of organs, and hairs. Thus, articulation morphology, also called open morphology, may be considered a new paradigm for plant morphology and plant morpho evo-devo. It transcends many long-standing controversies, problems, and pseudo-problems that have arisen since the publication of Goethe's Metamorphosis of Plants (1790).
Organisms, databases and tools