The study of plants, once known as botany, is today more frequently referred to as plant science. But to describe plant science as ‘the study of plants’ is uninformative: what exactly is plant science – what kinds of study and activity lie within its domain? If the study of plants warrants a special term then we assume there must be something about that study that is distinctive and special but that seems difficult to define. Perhaps the words have no meaningful content other than to convey the message that ‘We take plants seriously’, a couple of words that look good in a university handbook.
If plant science does have some special distinguishing characteristic(s) then that specialness is suggested by the word ‘science’. So what, then, are the defining characteristics of a ‘scientific’ study?
Current thinking in the philosophy of science suggests that although science has a number of well-accepted procedures (use of observation and experiment to test or falsify hypotheses, the formulation of general principles and laws, maximization of predictivity and so on) these cannot be claimed as being unique to science, even in combination. Contrary to popular belief and much intellectual scrutiny we have found that there is no scientific method, procedure, or unique form of logic that separates science from other modes of thinking and behaving so, at present, we must define science in a seemingly unsatisfactory or indefinite ways as, say, ‘the domain of activities, principles, procedures, and knowledge that we associate with the word ‘science”, or maybe ‘the most rigorous practical application of reason that we can muster in the analysis of the physical world’ (see Reason & science). For simplicity we can define science as a domain of knowledge and plant science that part of the scientific domain concerned with plants.
Science as progressive and cumulative knowledge
One useful way of thinking about science is as a form of progressive and cumulative knowledge. Science is progressive because new scientific knowledge helps us to map the physical world around us (and within us) in ways that allow us to manage it more effectively in practical and predictable ways, and it is cumulative because it is a body of shared knowledge that builds on the shared knowledge of the past. This is not unique to science but it give us an insight into the way that certain kinds of knowledge develop.
Categories of knowledge
In order to operate in the world we break it up conceptually into meaningful units, categories, or concepts (see classification). We use these categories to ‘map’ the physical world in ways that help us to understand, explain, and manage it in more effective ways. There are a number of categories that have proved particularly useful in the domain that we call science: they vary in degree of abstraction and include the names of objects and structures, the analysis of functions, definitions, classifications, principles, theories, laws, pictorial representations, and so on. If we refer to these elements of scientific knowledge as ‘categories’ then it is clear that science becomes the progressive and cumulative refinement of the categories that we use to understand and explain the physical world.
To gain a better understanding of the domain of plant science we can now trace the progressive and cumulative historical refinement of its knowledge categories.
The units of study: parts and wholes and their names
We take the physical components of the world for granted: the world consists of discrete physical objects like tables, chairs, planets, and olympic swimmers. But though regarding these as discrete objects we become ambivalent when we consider their relationship to other objects because paradoxically they are, at the same time, both discrete wholes themseves while at the same being parts of greater wholes: here we have a cognitive dissonance – almost any object is both a whole and part at the same time. A chair is a whole with legs as parts, but when we consider a room, the chair is not the whole but just a part.
When we consider the plant world in its totality today we think of ‘wholes’ as large as forests or as small as chloroplasts. In the continuum of wholes and parts should we consider any particular whole as more important than any other and, if so, then why? This matter will be discussed later under plant classification but for the time-being let’s look at the historical way that humans segregated the plant world into discrete units.
No doubt in prehistory both individuals and small bands of people recognised and named many more plants than most of us would recognise today. This is because they were totally dependent on the plants in their immediate environment. Though we are equally dependent on plants today our need for practical plant knowledge is much less because the plants we use for foods, medicines and materials of various kinds are supplied in quantity and variety by other people without my need to becomes involved in any way. I do not know how or where the vegetables I eat are grown and have no idea what plants are needed to produce the medicines I take. Much of the plant knowledge of our prehistoric ancestors would have been passed on by oral tradition but it was only with the advent of writing that this knowledge could be shared with a wider group of people and supplemented with additional names that could be passed on to future generations. Though small groups of people might build up a large bank of plant knowledge this knowledge could only become of permanent value when it was shared reliably within large communities. This situation only arose with the creation of stored written records which in their early days were probably far inferior to the oral knowledge of their times.
What were the plant units that were named? Though vegetation could be grouped and classified in many ways there were practical units – similar-looking plants that had always displayed similar properties when eaten or used in some way. The degree of discrimination of ‘kinds of plant’ would probably vary according to circumstances but we can tell from the earliest written records and anthropological reports that plants were almost always divided into general groups and then divided again more finely. So there were trees like oaks and eucalypts and within that broad group could be discerned smaller units. This is a virtually universal characteristic of folk taxonomy and as akin to the way humans often discriminate between themselves as being within a broad group or family, say the Smith family, but a particular individual within that family, John Smith. Science has taken over the practical units of folk taxonomy and used the terms ‘genus’ and ‘species’ to denote the two groups. Genus and species are a powerful combination because in just two words it is possible to summarize both likeness and difference.
So, only with the advent of writing could there be reliable, widespread, progressive, and cumulative plant knowledge. Though edible plants would always have been important, along with the skills to to distinguish between them, it was medicinal plants that became the subjects of study by medical experts, the physicians, in early civilizations. Medicinal knowledge had the power of life and death and was maintained, often in writing, by a priestly and academic class having religious and spiriual powers like the shamen and medicine men of prehistory. Those working in the fields would have been uneducated so the first European written records of plants that date back two to three millennia BCE consist of lists of medicinal plants written on papyrus, sometimes with descriptions of their medicinal properties.
Theophrastus, the father of plant science, who lived in Classical Greece in the fourth to third century BCE, wrote the first scientific accounts of plants incuding the names of many that grew outside Greece. During the period of the Roman empire an encyclopaedic list of plants was assembled by Pliny the Elder and a herbal or list of medicinal plants was also written by Dioscorides, a Greek soldier in the Roman army. Dioscorides’s Materia Medica and the earlier lists would become much copied into the European Middle Ages supplemented by plants known to the Arab world. Through the early Middle Ages even through the early days of printed books called Herbals, the legacy of known plants from antiquity and these times numbered no more than about 1000. Though we are familiar today with two-word (binomial) names like Jack Smith, such names were not used for plants until the eighteenth century. Up to that time it was conventional to use brief descriptions called phrase names.
See also People of plant science
In the wild
Shared written knowledge of plants could only be useful when the plants discussed could be recognised within a community of people having plant knowledge. Accumulation of this kind of knowledge was, in retrospect, extremely slow. Lists of plants dating back to the ancient civilizations of Egypt and Mesopotamia name about 250 different kinds of plants, many of these are recognizable today, while the two botanical tracts written by Theophrastus list 450-550 different kinds. A famous list of medicinal plants, a Materia Medica, was compiled by Pedanius Dioscorides, a Greek soldier in the Roman Army and this would serve as the basis for works of the Middle Ages up to and including the first printed books known as Herbals that continued into the seventeenth century. A vast encyclopaedia of the Classical world, Historia Naturae, was written at the time of the Roman Empire by Pliny the Elder and though it included quite a large section on plants it was largely compiled from earlier works adding nothing original.
By the end of the fifteenth century intellectual curiosity, which had previously looked backward to the authority of classical scholars and the scriptures, was now looking forwards as botanists, excited by the new Age of Discovery, began to speculate about the possible number of different plants in the world. The herbals had described 500-1000 species, this being the legacy of Classical and Medieval knowledge. In 1613 Jean Bauhin (1541-1613) (son of Jean Bauhin (1511-1582) who was physician to Jeanne d’Albret, Queen of Navarre) described about 4000 species. Jean’s brother Gaspard, in the Pinax of 1623, increased this number to 6000, his account including synonymy, references, and binomials over a century before they were used by Linnaeus. English botanist Ray’s three-volume Historia Plantarum (1686, 1688, 1704) lists some 18,700 different kinds of plants. Linnaeus, more than any other botanist, was aware of the importance of ensuring that communicated knowledge about plants would be in a form that was accessible to the community of plant scientists. He vastly facilitated the arrangement of plants into scientific groupings, the means of presenting the host of synonyms that were beginning to appear, the construction of an agreed terminology for plant description and the mode of description itself, the standardization of binomial nomenclature and much more. Linnaeus in 1753, less than 40 years before Australian settlement, believed that the total number of plant species in the world was unlikely to exceed 10,000 (Stearn 1959).
By the nineteenth century botanists were once again entering a new encyclopaedic phase as part of the aspirations of European empires. One compendium initiated by August de Candolle, Prodromus Systematis Naturalis Regni Vegetabilis, attempted to include all known seed plants, classified and described in 17 volumes, the last 10 volumes written by other authors (35 in all) and published by his son Alphonse (1823-1873); it included 58,000 species organised into 161 families. Englishmen George Bentham and Joseph Hooker (Director, Royal Botanic Gardens Kew) produced a major natural classification of seed plants Genera Plantarum (1862-1883) with 200 families and 7569 genera described in detail.
The task of making a global inventory of plant species fell into abeyance until facilitated by computer database technology. Today, in 2016, the total number of naturally-occurring seed plant taxa in the world is estimated to be about 369,000.
A World Flora Online Project (Missouri Botanical Garden, Royal Botanic Gardens, Kew, Royal Botanic garden Edinburgh and New York Botanical Garden) was initiated in 2012 in response to Target 1 of the Global Strategy for Plant Conservation with a widely accessible working list of known plant species now completed in 2010 as a step towards a complete world flora and an aim to halt the loss of plant species worldwide by 2020: see The Plant List (www.theplantlist.org).
By the 17th century Europe’s leading gardens, where the world’s leading botanists worked, were competing to hold the greatest number of different plants. In the 1660s the Jardin du Roi in Paris claimed about 4000 species (Stafleu 1969), probably the most extensive at this time, but by 1720 giving way to Leiden under Boerhaave with 5846 different kinds (Boerhaave 1720). Between 1730 and 1770 both the reputation and collection at the Chelsea Physic garden grew until the species totalled about 5000 (Uglow 2005, p. 147). John Hills’s Hortus Kewensis of 1769, an inventory of Kew’s stock, listed about 600 species. Then, following the 1768 edition of Miller’s Gardener’s Dictionary came Aiton’s three-volume Hortus Kewensis in 1789, a monumental descriptive inventory of Kew’s living collections now under Banks’s influence totalling over 5,500 species. This was an invaluable horticultural record that included Linnaean Latin diagnoses (much of it was written by botanists Solander, Dryander and Brown) and annotated with dates of introduction etc. It included ‘… almost all the species then cultivated in England’ (Stearn 1961, pp. cvii-cviii). The 1813 edition of Hortus Kewensis had swelled to five volumes and over 11,000 species including about 300 from Australia, indicating the further impact of Banks’s acquisitiveness (Turrill 1959, pp. 20-21, 23-24; Drayton 2000, p. 125). The Berlin Botanic Garden, effectively founded by Karl Willdenow in 1801, by the time of his death in 1812, contained about 7,700 species.
In 2015 it is likely that more than 120,000 different kinds of plants (this includes cultivars) were being cultivated in British gardens (Armitage, pers. comm.), but it is not sure whether the total number is increasing or decreasing. In Australia the total is at least 26,000. The Royal Botanic Gardens Kew today cultivates 4,141 genera, and 11,557 species and the herbarium contains about 7 million specimens and over 95% of known flowering plant genera.<sup
As more kinds of plants were recorded, and from more dispersed regions, there was an increasing need for improved descriptions that would help distinguish the different kinds, otherwise the lists of names would become useless. Having established a small core of different kinds of plants growing in dispersed regions of Europe it was now necessary to provide descriptions that would allow one kind to be sorted out from the others. If this could not be done then the potential shared knowledge that was embedded in lists of plants would have no general benefit. Plant identification thus required a mutually agreed system, or terminology, for plant structures.
Once there was an agreed list of different plant kinds together with an agreed terminology for plant structures then communication between plant people was greatly facilitated, including discussion of plant function.
Though there is ample room for disagreement about not only the names of plant structures but what constitutes a structure worthy of special recognition in a name in the first place. This situation is made vastly more complicated when we come to consider the aspect of dynamic change in plants. This is the aspect of botany where theory has been most evident. How do we explain all the life processes that go on in a plant, its morphological development and nutrition? This is an active area of research today. Among the breakthroughs can be listed theories accounting for germination, dormancy, transpiration, respiration, photosynthesis, hormonal control (tropisms and nastys), photoperiodism and circadian rhythms, seasonality.
Today we regard plant physiology as a process of reverse-engineering the unconscious purpose of plant function that is a consequence of natural selection.
The scope of plant science disciplines
Regardless of questions concerning the nature of plant science we need to examine what it is that people who call themselves plant scientists do, because one answer to our question about the meaning of plant science is that it is all those activities, principles, and procedures that are used by plant scientists.
One primary goal of science is the refinement of the shared categories we use to describe the physical world: this includes the basic units of study (named taxa or taxonomic groups, most familiar today as genera and species) and the way these groups are related to one-another, and the structures that these units possess (a standardised terminology for their parts wit ha greement on the parts that warrant categorization). As all organisms are functionally organized then part of the scientific process entails the understanding of these functions (see purpose). As an aid to communication it is therefore possible to provide improved descriptions of taxa and their relationships, including their structures and functions and in this way botanical science can be understood as both progressive and cumulative. It is progressive because it leads to a better understanding of plant structure and function with all the practical consequences that this entails, and it is cumulative since knowledge of plant structure expanded from simple morphology to encompass anatomy, cytology, physiology, biochemistry and much more. Botany, once one part of medicine, is now itself fragmented into myriad specialist disciplines including those dealing with particuar parts of the plant kingdom.
The scope of plant science(to be worked up)
Our minds process information by breaking it up into adaptively meaningful cognitive categories (concepts, units of representation) – what we can call cognitive segregation. To operate in the world we do not think about these categories all at once but arrange or classify them into convenient groups depending on our particular interest or concern – our current frame of reference – what we can call our cognitive focus. Our cognitive focus is mostly directed towards our perception, the physical needs of the moment, and tasks of the day. Science, however, focuses on the categories that map the physical world as accurately as possible through the theories, names, properties, definitions, laws and other categories that we use in the scientific enterprise.
As the number of items to be classified increases, so the classification itself tends to become more complex and finely resolved. Conversely smaller numbers lend themselves to greater simplicity. In the mid twentieth century the natural sciences were simply divided into four primary domains: Biology, Geology, Physics, and Chemistry. But the accumulation of knowledge in recent times has made these categories seem less distinct as disciplines have tended to merge more into one-another.
In relatively recent times bacteria and fungi have been separated from the plant kingdom and the study of plants divided into a large number of disciplines. Beginning with taxonomy we see the study of structure divided into external factors (morphology) and internal structures (anatomy), and physiology. From the ?17th people begin to specialize in particular segments of the plant kingdom, so we have bryology (mosses and liverworts), pteridology (ferns), phycology (algae), mycology (fungi). There is the specialist study of fossil plants or palaeobotany. Nowadays plant structure is the basis of specialist disciplines dealing with particular structures so palynology is the study of pollen and carpology the study of fruits. Ultrustructure (structures revealed by electron microscopy), taxonomy, morphology while ‘dynamic’ and developmental process are studied by physiology and embryology while advances in chemistry have made it possible to study processes occurring at a molecuar level through biochemistry. The advent of Darwin‘s theory of natural selection resulted in evolutionary biology or phylogeny. Former subjects like taxonomy have taken on modern techniques so that while taxonomy was once largely a matter of morphology (sometimes called alpha taxonomy), today we have molecular systematics, chemotaxonomy, cladistics, phylogenetic systematics, genomics, informatics. More applied disciplines like horticulture and agriculture are themselves subdivided into subdisciplinary categories and categories can intergrade to varying degrees as we consider hybrid categories like economic botany, phylogenetic systematics, horticultural botany and so on. Agricultural botany, and pharmacognosy. The principles and techniques of many modern disciplines are applicable across the biological world as is the case with genetics and pathology. At a more inclusive scale the role of plants within ecosystems has been addressed through the discipline of ecology.
The impact of technology
Technology, which is a product of science, has extended our perception of the world from that of our evolved everyday sense experience and plant characters or morphology evident to the naked eye, to include objects viewed at very different scales. The first major invention to impact on botany was the microscope which effectively opened up an entirely new world that required decisions about its own units of study, structures and functions. It was now possible to provide scientific explanations at a different scale as the discipline of cell biology (cytology) opened up, delving in even more detail with the invention of the scanning electron microscope with the structures and functions at a scale below that of the cell in discipline known as ultrastructure (fine structure). Rapid advances in organic chemistry meant that theories concerning molecular processes in the plant could be postulated in the new field of plant chemistry (biochemistry, molecular biology) and of special interest were the macromolecues of DNA found in the cell chromosomes that determined so much of the plant’s structure and function through studies known as genetics. The interpretation of the role of plants within world vegetation has beengreatly facilitated by computers, aerial photography, satellite imagery, GPS and the like.
New categories require new classifications that incorporate the new categories and which divide the objects being classified to a finer resolution.
Citations & notes
 Morton 1981, p. 145
 Royal Botanic Gardens Kew, 2016
 Hyams & MacQuitty 1969, p. 76
Hyams, E. & MacQuitty, W. (1969). Great botanical gardens of the World. London: Bloomsbury Books
Royal Botanic Gardens Kew 2016. The State of the World’s Plants Report – 2016. Royal Botanic Gardens, Kew