"Father of Botany"
Palermo Botanic Gardens
The first steps in the history of botany would have been taken with the empirical plant lore passed from generation to generation in the oral traditions of our paleolithic hunter-gatherer ancestors. The written record of plants dates from the Neolithic Revolution as the domestication of plants and animals was established in settled agricultural communities around the world about 2,500 to 10,000 years ago. The first clear indication of a critical curiosity for plants themselves, rather than their uses, appears in the teachings of Aristotle’s student Theophrastus at the Lyceum in ancient Athens in about 350 BC. In Europe this early glimpse of botanical science was soon enveloped by the Middle Ages and a preoccupation with medicinal plants that lasted more than 1000 years during which the medicinal works of classical antiquity were reproduced again and again in manuscripts and books called herbals while in China and the Arab world, the Greco-Roman work on medicinal plants was carefully preserved and extended – but only as a medicinal record.
The European Renaissance of the 14th – 17th centuries heralded a scientific revival during which botany gradually emerged from natural history as an independent science distinct from medicine and agriculture.Herbals were replaced by Floras, books that described the native plants of local regions. The invention of the microscope stimulated the study of plant anatomy and the first carefully designed experiments in plant physiology were performed. With the expansion of trade and exploration beyond Europe the many new plants being discovered were subjected to an increasingly rigorous process of description, classification and naming.
From these beginnings have radiated the myriad contemporary plant sciences ranging from the applied fields of economic botany in its many forms (notably agriculture, horticulture and forestry), to the continued study of plants and their interaction with the environment over many scales from the large-scale global significance of vegetation and plant communities (biogeography and ecology) through to the small scale of cell theory and molecular biology.
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Introduction
Botany (Greek Βοτάνη - grass, fodder; Medieval Latin botanicus – herb, plant)[1] and zoology are historically the core disciplines of biology (not named as such until the early 19th century) whose history is closely associated with the natural sciences chemistry, physics and geology. A distinction can be made between botanical science in a pure sense, as the study of plants themselves, and botany as applied science, which relates more to the human use of plants (also referred to as economic botany or ethnobotany). Early natural history divided pure botany into three main streams morphology-classification, anatomy and physiology.[2] Most notable of the topics in applied botany are horticulture, forestry and agriculture but, less obviously, topics like weed science, plant pathology, floristry, pharmacognosy and others. However, in mainstream botany over time there has been a progressive diversification and integration of disciplines with more and more subjects and subject combinations arising. Modern molecular systematics, for example, includes the techniques of taxonomy, molecular biology, computer science and more.
Within botany there are a number of subdisciplines focusing on special plant groups, each with a full range of related studies: included here are: phycology (algae), pteridology (ferns), bryology (mosses and liverworts) and palaeobotany (fossil plants). Fungi are now placed in a separate kingdom so mycology, once a botanical discipline, is now treated elsewhere.
Ancient and medieval knowledge
It must be assumed that, of necessity, nomadic hunter-gatherer societies passed on by oral tradition their empirical findings about different kinds of plants and their use as food, shelter, poisons, medicines, for ceremony and so on, this being embedded in the folk-taxonomies of pre-literate societies.[3] The nomadic life-style was drastically changed with the formation of settled communities in about twelve centres around the world during the Neolithic Revolution from about 10,000 to 2500 years ago. This marked the domestication of plants and animals, the emergence of the written word, along with increasingly sophisticated technology and the formation of the social structure of civilization as we define it today.
Plant lore and plant selection
All staple foods were domesticated in prehistoric times as higher-yielding varieties were produced in a selection process that took hundreds to thousands of years; important here are legumes on all continents, rice in East Asia, wheat and barley in the Middle east, and maize in Central and South America. By Greco-Roman times named varieties of many of the popular food plants of today, including grapes, apples, figs, and olives, were being listed in manuscripts.[4] Botanist William Stearn has pointed out that "cultivated plants are mankind’s most vital and precious heritage from remote antiquity”.[5]
It is from the Neolithic in about 3000 BCE that we have the first known illustrations of plants[6] and descriptions of gardens in Egypt.[7] However protobotany, the first pre-scientific written record of plants, did not begin with food; it was born out of the medicinal literature of Egypt, China, Mesopotamia and India.[8] Botanical historian Alan Morton notes that agriculture was the occupation of the poor and uneducated, while medicine was the realm of socially influential shamans, priests, apothecaries, magicians and physicians, who were more likely to record their knowledge for posterity.[9]
Theophrastus and the origin of botanical science
Ancient Greece of the 6th century BCE was a vibrant centre at the confluence of Egyptian, Mesopotamian and Minoan cultures at the height of Greek colonisation of the Mediterranean: here there emerged a genuine non-anthropocentric curiosity about plants themselves rather than the uses that could be made of them. Philosophical thought of this period ranged freely through many subjects. Empedocles (490–430 BCE) foreshadowed Darwinian evolutionary theory in a crude formulation of the mutability of species and natural selection.[10] The physician Hippocrates (460– 370 BCE) avoided the prevailing superstition of his day and approached healing by close observation and the test of experience. The major works written about plants extended beyond the description of their medicinal uses to the topics of plant geography, morphology, physiology, nutrition, growth and reproduction.
Fresco in Apostolic Palace, Rome, Vatican City, by Raphael 1509-1510
Theophrastus of Eressus (Greek: Θεόφραστος; c. 371 – 287 BCE), often referred to as the ”Father of Botany”, was a student and close friend of Aristotle (384–322 BCE) who he succeeded as head of the Lyceum (a place of learning like a modern university) in Athens with its tradition of peripatetic philosophy. The Lyceum prided itself in a tradition of systematic observation of causal connections, critical experiment and rational theorizing. Theophrastus challenged the superstitious medicine employed by the physicians of his day, called rhizotomi, and also the control over medicine exerted by priestly authority and tradition.[11] In the garden at the Lyceum were many plants collected in distant lands and here he gained much of his plant knowledge.[12] Together with Aristotle he had tutored Alexander the Great whose military conquests were carried out with all the scientific resources of the day, the Lyceum garden probably containing many botanical trophies collected during his camapaigns.[13]
Theophrastus's major botanical works were the Enquiry into Plants and Causes of Plants which were his lecture notes for the Lyceum.[14] The opening sentence of the Enquiry reads like a botanical manifesto: “We must consider the distinctive characters and the general nature of plants from the point of view of their morphology, their behaviour under external conditions, their mode of generation and the whole course of their life”. The Enquiry is 9 books of "applied" botany dealing with the forms and classification of plants and economic botany, examining the techniques of agriculture (relationship of crops to soil, climate, water and habitat) and horticulture. He described some 500 plants in detail often including descriptions of habitat and geographic distribution and he recognised some plant groups that can be distinguished as modern-day plant families. Names he used, like Crataegus, Daucus and Asparagus remain today. His second book Causes of Plants covers plant growth and reproduction (akin to modern physiology).[15] Like Aristotle he grouped plants as "trees", "undershrubs", "shrubs" and "herbs" but also distinguished annuals, perennials and biennials; monocotyledons and dicotyledons; he noted the difference between determinate and indeterminate growth, also details of floral structure including the degree of fusion of the petals, position of the ovary and more.[16][17] In these lecture notes of Theophrastus we have the first clear exposition of the rudiments of plant anatomy, physiology, morphology and ecology — presented in a way that would not be matched for another eighteen centuries.[18]
Meanwhile the study of medicinal plants was not being neglected and a full synthesis of ancient Greek pharmacology was compiled in Materia Medica c. 60 CE by Pedanius Dioscorides (c. 40-90 CE) who was a Greek physician with the Roman army. This work proved to be the definitive text on medicinal herbs, both oriental and occidental, for fifteen hundred years until the dawn of the European Renaissance being slavishly copied throughout this period.[19] Though rich in medicinal information with descriptions of about 600 medicinal herbs, the botanical content of the work was extremely brief.[20]
Ancient Rome
The Romans, though contributing little to the firm foundations of botanical science that had been laid by the Greeks, nevertheless thoroughly explored the applied botany of agriculture. In works titled De Re Rustica the principles and practice of agriculture were discissed by the writers Cato the Elder (234–149 BCE), Marcus Varro (116–27 BCE) and, in particular, Columella (4–70 CE).[21] Roman encyclopaedist Pliny the Elder (23–79 CE) deals with plants in Books 12 to 26 of his 37-volume highly influential work Naturalis Historia where he frequently quotes Theophrastus but with little botanical insight. He does, nevertheless, make a distinction between true botany on the one hand, and farming and medicine on the other.[22]
It is estimated that at the time of the Roman Empire between 1300 and 1400 plants had been recorded in the West.[23]
Medicinal plants of the early Middle Ages
In Western Europe, after Theophrastus, botany passed through a bleak period of 1800 years when little progress was made and, indeed, many of the early insights were lost. As Europe entered the Middle Ages, a period of disorganised feudalism and indifference to learning, China, India and the Arab world enjoyed a golden age. Chinese philosophy had followed a similar path to that of the ancient Greeks. The Chinese dictionary-encyclopaedia Erh Ya (traditional Chinese 爾雅, simplified Chinese 尔雅) probably dates from about 300 BCE and describes about 334 plants classed as trees or shrubs, each with a common name and illustration. Between 100 and 1700 CE many new works on pharmaceutical botany were produced including encyclopaedic accounts and treatises produced for the Chinese imperial court. These were free of superstition and myth, and there was a high standard of description and nomenclature, as well as cultivation information and notes on economic and medicinal uses — even elaborate monographs on ornamental plants. But there was no experimental method, analysis of the plant sexual system, nutrition, or anatomy.
The 400-year period from the 9th to 13th centuries CE was the Islamic Renaissance when Islamic culture and science thrived. During this Islamic Golden Age Greco-Roman texts were preserved, copied and extended although new texts always emphasised the medicinal aspects of plants. Kurdish biologist Ābu Ḥanīfah Āḥmad ibn Dawūd Dīnawarī (828–896 CE) (Arabic: ابوحنیفه احمد بن داود دینوری) is known as the founder of Arabic botany; his Kitâb al-nabât (‘Book of Plants’) describes 637 species, discussing plant development from germination to senescence and including details of flowers and fruits.[24] The Mutazilite philosopher and physician Ibn Sina (Avicenna) (c.980–1037) was another influential figure, his The Canon of Medicine, being a landmark in the history of medicine until the Enlightenment, but with limited botanical content.[25] Ibn al-Baitar (Arabic: ابن البيطار) (circa, 1188 - 1248) was an eminent Arab scientist considered one of the greatest scientists of Al-Andalus (Andalusia). His Kitab al-Jami fi al-Adwiya al-Mufrada (Arabic: كتاب الجمع في الأدوية المفردة) was a pharmacopoeia describing 1400 species, 300 of which he discovered himself. Translated into Latin in 1758 this was used in Europe until the early 19th century[26] as a critical summing up of many centuries of Arab pharmacology.[27]
In India simple artificial plant classification systems of the Rigveda, Atharvaveda and Taittiriya Samhita became more botanical with the work of Parashara (c.400–500 CE), the author of Vṛksayurveda (the science of life of trees). He made close observations of cells and leaves and divided plants into Dvimatrka (Dicotyledons) and Ekamatrka (Monocotyledons). The dicotyledons were further classified into groupings (ganas) akin to modern floral families: Samiganiya (Fabaceae), Puplikagalniya (Rutaceae), Svastikaganiya (Cruciferae), Tripuspaganiya (Cucurbitaceae), Mallikaganiya (Apocynaceae), and Kurcapuspaganiya (Asteraceae).[28][29]
The Age of Herbals
In the European Middle Ages of the 15th and 16th centuries the lives of 90% of European citizens were based around agriculture. Even so, when printing arrived, with its facility to use movable type and woodcut illustrations, it was not treatises on agriculture that were published but lists of medicinal plants with descriptions of their properties or "virtues" as they were termed. These first plant books, known as herbals, marked a time when botany was still one part of medicine as it had been for most of ancient history.[25] Authors of herbals were often curators of university gardens[30] and most herbals were derivative compilations of classic texts, notably De Materia Medica. However, the need for accurate and detailed plant descriptions meant that some herbals were more botanical than medicinal. German Otto Brunfels's (1464-1534) Herbarum Vivae Icones (1530) contained accurate illustrations and about 47 species that were new to science. His fellow countryman Hieronymus Bock's (1498-1554) Kreutterbuch of 1539 described plants found in his local woods and fields and these were beautifully illustrated in the 1546 edition.[31] However, it was Valerius Cordus (1515-1544) who pioneered the formal botanical description that detailed both flowers and fruits, some anatomy including the number of chambers in the ovary, and the type of ovule placentation. He also made observations on pollen and distinguished between inflorescence types.[31] His work, the 5 volume Historia Plantarum, was published by Swiss Conrad Gesner in 1561-1563, about 18 years after his early death aged 29. In Holland Rembert Dodoens (1517-1585) in Stirpium Historiae (1583) included descriptions of many new species from the Netherlands in a scientific arrangement[32] and in England William Turner (1515-1568) in his Libellus De Re Herbaria Novus (1538) published names, descriptions and localities of many native British plants.
Herbals contributed to botany by setting in train the science of plant description, classification, and botanical illustration. Up to the seventeenth century botany and medicine were one and the same but those books emphasising medicinal aspects eventually omitted the plant lore to become modern pharmacopoeias; those that omitted the medicine became more botanical and evolved into the modern compilations of plant descriptions we call Floras. These were often backed by herbaria, collections of dried plants that verified the plant descriptions given in the Floras and in this way modern botany, especially plant taxonomy, was born out of medicine.[33]
The European Renaissance and after 1550–1800
The European Renaissance with its revival of learning resulted in a reinvigorated interest in plants. The church, feudal aristocracy and an increasingly influential merchant class that supported science and the arts, now jostled in a world where increasing trade and exploration returned botanical treasures to the large public, private, and newly established botanic gardens, and introduced an eager population to novel crops and drugs from Asia, the East Indies and the New World. Botany in the 17th century became an independent science as plant description and classification was finally divorced from medicine, and the number of scientific publications increased. In England, for example, increased interest was due to the influence of the Royal Society, specialist societies like the Linnaean Society; the support and activities of botanical institutions like the Chelsea Physic Garden, Royal Botanic Gardens Kew, and the Oxford and Cambridge Botanic Gardens, and the influence of private and commercial gardens of eminent nurserymen.[34] All this along with a renewed interest in the description of native plants and local flora heralded a new phase of description and identification.
Botanical gardens and herbaria
Both public and private gardens form a constant background to the historical unfolding of botanical science. Early botanical gardens were physic gardens, repositories for the medicinal simples or officinals described in the herbals. As they were generally associated with universities or other academic institutions the plants were also used for study. The directors of these gardens were eminent physicians with an educational role as “scientific gardeners” and it was staff of these institutions that produced many of the published herbals.
The botanical gardens of the modern tradition were established in northern Italy, the first being at Pisa (1544), founded by Luca Ghini (1490-1556). Collections of pressed and dried specimens were called a hortus siccus (garden of dry plants) and the first accumulation of plants in this way for study is attributed to Luca Ghini.[35] Buildings called herbaria housed these specimens mounted on card with descriptive labels. Stored in cupboards in systematic order they could be preserved in perpetuity like this, and it also allowed the exchange of specimens with other institutions, a practice of descriptive and systematic botany that has been used to this day. It is claimed that Ghini invented the first plant press and compiled the first herbarium.[36]
By the eighteenth century the physic gardens had been transformed into "order beds" that demonstrated the classification systems that were being devised by botanists of the day, their modern day equivalents being known as "systems gardens", but first they had to accommodate the influx of botanical trophies of curious, beautiful and new plants that were the result of horticultural exploration and the first stirrings of European colonial expansion.
The 15th and 16th centuries had seen the emergence of botany from herbal medicine encouraged by the invention of printing, the emergence of botanic gardens with their associated herbaria, and stimulated by the improved ship navigation that facilitated scientific exploration and expeditions.
Herbal to Flora
During the seventeenth and eighteenth centuries plant description and classification now related plants to one-another and not to man. This marked a return to the non-anthropocentric botanical science promoted by Theophrastus over 1500 years before and, coupled with the new system of binomial nomenclature resulted in "scientific herbals" called Floras that detailed and illustrated the plants growing in particular regions.[37] The seventeenth century also marked the beginning of experimental botany and a more rigorous scientific method, while improvements in the microscope launched the new discipline of plant anatomy whose foundations, laid by the careful observations of Englishman Nehemiah Grew and Italian Marcello Malpighi, would last for 150 years.[38]
Botanical exploration
Meanwhile descriptive accounts of plants in foreign lands continued – for the West Indies (Hans Sloane (1660–1753)), China (James Cunningham); and the Moluccas (George Rumphius (1627–1702)). Exploration continued with collections for herbaria and new descriptions in China and Mozambique (João de Loureiro (1717-1791)), West Africa (Michel Adanson (1727–1806)) who devised his own classification scheme and forwarded a crude theory of the mutability of species; (Joseph Banks (1743–1820) visited Canada, circumnavigated the world with Captain James Cook (1728–1779), and in 1772 visited the Hebrides and Iceland.[39] Even so, the motivation for collecting in woods, fields and foreign lands was, in the first instance, medicinal.
Classification and morphology
Plant classifications have changed over time from "artificial" systems based on general habit and form, to pre-evolutionary "natural" systems expressing similarity using one to many characters, then post-evolutionary phylogenetic "natural" systems that use characters in a way that captures evolutionary relationships.[40]
Italian physician Andrea Caesalpino (1519-1603) studied medicine and taught botany at the University of Pisa for about 40 years eventually becoming Director of the Botanic Garden of Pisa from 1554 to 1558. His 16–book De Plantis (1583) describes 1500 plants and his herbarium of 260 pages and 768 mounted specimens still remains. Caesalpino moved away from characters of form and habit to those of flower and fruit including the structure and morphology of seeds; he also applied the concept of the genus.[41] He was the first to try and derive principles of natural classification reflecting the overall similarities between plants and he produced a classification scheme well in advance of its day.[42] Gaspard Bauhin (1560–1624) produced two influential publications Prodromus Theatrici Botanici (1620) and Pinax (1623). These brought order to the 6000 species now described and in the latter he used binomials and synonyms that may well have influenced Linnaeus's thinking. He also insisted that taxonomy should be based on natural affinities.[43]
To sharpen the precision of description and classification Joachim Jung (1587–1657) compiled a much-needed botanical terminology which has stood the test of time. English botanist John Ray (1623–1705) built on Jung’s work to establish the most elaborate and insightful classification system of the day.[44] His observations started with the local plants of Cambridge where he lived, with the Catalogus Stirpium circa Cantabrigiam Nascentium (1860) which later expanded to his Synopsis Methodica Stirpium Britannicarum, essentially the first British Flora. Although his Historia Plantarum (1682, 1688, 1704) provided a step towards a world Flora as he included more and more plants from his travels, first on the continent and then beyond. He extended Caesalpino’s natural system with a more precise definition of the higher classification levels deriving many modern families and he thought that all parts of plants were important in classification. He recognised that variation arises from both internal (genotypic) and external environmental (phenotypic) causes and that only the former was of taxonomic significance. He was also among the first experimental physiologists. The Historia Plantarum can be regarded as the first botanical synthesis and text book for modern botany. According to botanical historian Alan Morton, Ray "influenced both the theory and the practice of botany more decisively than any other single person in the latter half of the seventeenth century".[45] Ray's family system was later extended by Pierre Magnol (1638–1715) and Joseph de Tournefort (1656–1708), a student of Magnol, achieved notoriety for his botanical expeditions, his emphasis on floral characters in classification, and for reviving the idea of the genus as the basic unit of classification.[46]
By the middle of the eighteenth century, the era of exploration and its vast botanical booty accumulating in gardens and herbaria was in dire need of cataloguing and synthesis. It was Swede Carl Linne (known by his Latinised name Carolus Linnaeus) (1707–1778) who set about this task. He adopted a sexual system of classification using stamens and pistils as important characters. Among his most important publications were Systema Naturae (1735), Genera Plantarum (1737), and Philosophia Botanica (1751) but it was in his Species Plantarum (1753) that he gave every species a binomial thus setting the path for the future accepted method of designating the names of all organisms. His sexual system was later elaborated by Bernard de Jussieu (1699–1777) whose nephew Antoine-Laurent de Jussieu (1748–1836) extended yet again to include about 100 orders (present-day families).[47] Frenchman Michel Adanson (1727–1806) in his Familles des Plantes (1763, 1764), apart from extending the current system of family names, emphasized that a natural classification must be based on a consideration of all characters, even though these may later be given different emphasis according to their diagnostic value for the particular plant group. Adanson's method has, in essence, been followed to this day.[48]
Eighteenth century plant taxonomy bequeathed to the nineteenth century clear ideas of the family, genus and species, a precise binomial nomenclature and botanical terminology, and a system of classification based on natural affinities.
Anatomy
In the first half of the eighteenth century botany was still preoccupied with the core business of identification, description, classification and nomenclature but the field of investigation was beginning to widen. Although the microscope was invented in 1590 it was only in the late 17th century that lens grinding by Antony van Leeuwenhoek gave the resolution needed to make major discoveries. Early general biological observations were made by Robert Hooke (1635–1703) but the solid foundations of plant anatomy were laid by Italian Marcello Malpighi (1628–1694) of the University of Bologna in his Anatome Plantarum (1675) and Royal Society Englishman Nehemiah Grew (1628–1711) in his The Anatomy of Plants Begun (1671) and Anatomy of Plants (1682). These botanists rigorously explored what we would now call developmental anatomy and morphology, tracing the process from seed to mature plant recording stem and wood formation, and discovering and naming parenchyma and stomata in the process.[49]
Physiology
In plant physiology the movement of sap and the absorption of substances through the roots was being investigated. Jan Helmont (1577–1644) by experimental observation and calculation, noted that the increase in weight of a growing plant cannot be derived purely from the soil, and concluded it must relate to water uptake.[50] Englishman Stephen Hales (1677–1761) established by quantitative experiment that there is uptake of water by plants and a loss of water by transpiration and that this is influenced by environmental conditions: he distinguished “root pressure, “leaf suction” and “imbibition” and also noted that the major direction of sap flow in woody tissue is upward. His results were published in Vegetable Staticks (1727) He also noted that “air makes a very considerable part of the substance of vegetables”.[51] English chemist Joseph Priestly (1733–1804) is noted for his discovery of oxygen (as now called) and its production by plants. Later Jan Ingenhousz (1730–1799) observed that only in sunlight do the green parts of plants absorb air and release oxygen, this being more rapid in bright sunlight while, at night, the air (CO2) is released from all parts. His results were published in Experiments upon vegetables (1779) and with this the foundations for twentieth century studies of carbon fixation were laid. From his observations he sketched the cycle of carbon in nature even though the composition of carbon dioxide was yet to be resolved.[52] Studies in plant nutrition had also progressed. In 1804 Nicolas-Théodore de Saussure's (1767–1845) Recherches Chimiques sur la Végétation was an exemplary study of scientific exactitude that demonstrated the similarity of respiration in both plants and animals, that the fixation of carbon dioxide includes water, and that just minute amounts of salts and nutrients (which he analysed in chemical detail from plant ash) have a powerful influence on plant growth.[53]
Plant sexuality
Much was learned about plant sexuality by unravelling the reproductive mechanisms of mosses, liverworts and algae. In his Vergleichende Untersuchungen of 1851 Wilhelm Hofmeister (1824–1877) starting with the ferns and bryophytes demonstrated the process of sexual reproduction in plants as an “alternation of generations” between sporophytes and gametophytes.[54]. This initiated the new field of comparative morphology which, largely through the work of William Farlow (1844–1919), Nathanael Pringsheim (1823–1894) and Celakowski (1834–1902), Frederick Bower and Eduard Strasburger put on sound foundations the fact of alternation of generations throughout the plant kingdom.[55] However, it was Rudolf Camerarius (1665–1721) who was the first to establish plant sexuality conclusively by experiment. He declared in a letter to a colleague dated 1694 and titled De Sexu Plantarum Epistola that “no ovules of plants could ever develop into seeds from the female style and ovary without first being prepared by the pollen from the stamens, the male sexual organs of the plant".[56]
It was some time before German academic natural historian Joseph Kölreuter (1733–1806) extended this work by noting the function of nectar in attracting pollinators and the role of wind and insects in pollination. He also produced deliberate hybrids, observed the microscopic structure of pollen grains and how the transfer of matter from the pollen to the ovary inducing the formation of the embryo.[57] One hundred years after Camerarius, in 1793, Christian Sprengel (1750–1816) broadened the understanding of flowers by describing the role of nectar guides in pollination, the adaptive floral mechanisms used for pollination, and by demonstrating that cross-pollination was the rule, even though male and female parts are usually together on the same flower.[58]
Nineteenth century foundations of modern botany
From 1840 there was a shift in work practices from the production of weighty tomes by authoritative individuals and "gentlemen scientists", to the publication of “papers” that emanated from research “schools” that promoted the questioning of conventional wisdom. Part of this process started in the late 18th century when specialist journals began to appear.[59] Botany was greatly stimulated by the publication of the first “modern” text book, Matthias Schleiden's (1804–1881) Grundzuge der Wissenschaftlichen, published in English in 1849 as Principles of Scientific Botany which moved away from taxonomy and plant description as the primary focus of botanical research.[60] By 1850 an invigorated organic chemistry had revealed the structure of many plant constituents.[61] The great era of plant classification had now passed but the work continued. Augustin de Candolle (1778-1841) was successor to Antoine-Laurent de Jussieu and he edited the massive Prodromus Systematis Naturalis Regni Vegetabilis (1824-1841) with 34 other authors: it contained all the dicotyledons known in his day, some 58000 species in 161 families, and he doubled the number of recognized plant families, the work being completed by his son Alphonse (1806-1893) in the years from 1841 to 1873.[62]
Plant geography and ecology
The opening of the nineteenth century was marked by an increase in interest in the connection between climate and plant distribution. Carl Willdenow (1765–1812) examined the connection between seed dispersal and distribution, the nature of plant associations and the impact of geological history. He noticed the similarities between the floras of N America and N Asia, the Cape and Australia, and he explored the ideas of “centre of diversity" and "centre of origin”. German Alexander von Humbolt (1769–1859) and Frenchman Aime Bonpland (1773–1858) published a massive 30 volume work of their travels; Robert Brown (1773–1852) noted the similarities between the floras of S Africa, Australia and India while Joakim Schouw (1789–1852) explored more deeply than enyone else the influences of temperature, edaphic factors, soil water and light, and this was supplemented by work of Alphonse de Candolle (1806–1893). Joseph Hooker (1817–1911) pushed the boundaries of floristic studies with his studies of Antarctica, India and the Middle East closely assessing the phenomenon of endemism. August Grisebach (1814–1879) in Die Vegetation der Erde (1872) examined physiognomy in relation to climate and in America geographic studies wee pioneered by Asa Gray (1810–1888).
Physiological plant geography, perhaps more familiarly termed ecology, emerged out of floristic biogeography in the late nineteenth century as environmental influences on plants received greater recognition. Early work in this area was synthesised by Copenhagen professor Eugenius Warming (1841–1924) in his book Plantesamfund (Ecology of Plants) including new ideas on plant communities, their adaptations and environmental influences. This was followed by another grand synthesis, the Pflanzengeographie auf Physiologischer Grundlage of Andreas Schimper (1856–1901) in 1898 (published in English in 1903 as Plant-geography upon a physiological basis translated by W.R. Fischer, Oxford: Clarendon press, 839 pp.)[63]
Anatomy
During the nineteenth century German scientists led the way in the production of a unitary theory of the structure and life-cycle of plants. Following improvements in the microscope at the end of the 18th century, Charles Mirbel (1776–1854) in 1802 published his Traité d'Anatomie et de Physiologie Végétale and Johann Moldenhawer (1766–1827) published Beyträge zur Anatomie der Pflanzen (1812) in which he describes techniques to separate the cells from the middle lamella layer that separates them. He identified vascular and parenchymatous tissues, described vascular bundles, observed the cells in the cambium, and interpreted tree rings. He found that stomata were composed of pairs of cells, rather than a single cell with a hole.
Plant anatomy studies on the stele were consolidated by Carl Sanio (1832–1891) who studied the secondary tissues and meristem including cambium and its action. All this and more was synthesized in the encyclopaedic comparative anatomy of Heinrich Anton de Bary in 1877. A synthesis of the stele in root and stem was completed by Van Tieghem (1839–1914) and of the meristem by Karl Nägeli (1817–1891). To these findings can be added extensive studies on the origins of the carpel and flower that continue to the present day.
Water relations
Hugo von Mohl (1805–1872), who summarized work in anatomy leading up to 1850 in Die Vegetabilische Zelle (1851), also explored solute transport and the theory of water uptake by the roots using cohesion, transpirational pull, capillarity and root pressure.[61] To this list of German achievement can be added the definitive textbook on plant physiology synthesising the work of this period, Sach's Vorlesungen über Pflanzenphysiologie of 1882. Non-German advances were made in the early exploration of geotropism (the effect of gravity on growth) by Englishman Thomas Knight, together with the discovery and naming of osmosis by Frenchman Henri Dutrochet (1776–1847).[64]
Cytology
Recognition of the overall cellular structure of organisms, with each cell possessing all the characteristics of life, is attributed to the combined efforts of botanist Matthias Schleiden and zoologist Theodor Schwann (1810–1882) in the early nineteenth century, although Moldenhawer had already demonstrated that plants were wholly cellular with each cell having its own wall while Julius von Sachs pioneered studies of protoplasm and its continuity through cell walls.[65]
Between 1870 and 1880, through the collective work of many researchers, it was determined that a nucleus is never formed anew but always derived from the substance of another nucleus and in 1882 Flemming observed the longitudinal splitting of chromosomes in the dividing nucleus and concluded that each daughter nucleus received half of each of the chromosomes of the mother nucleus. Then by the early 20th century it was clear that the number of chromosomes in a given species is constant. With genetic continuity confirmed and the finding by Eduard Strasburger that the nuclei of reproductive cells (in pollen and embryo) have a reducing division (halving, now known as meiosis) the field of heredity was opened up. By 1926 Thomas Morgan was able to outline a theory of the gene and its structure and function. The form and function of plastids received similar attention, the association with starch being noted at an early date.[66] Other workers showed that all cells come from the division of other cells and with the study of cell division and analysis of the structure of protoplasm and the cell wall, and the structure and function of the nucleus (which had been discovered by Robert Brown in 1831), plastids and vacuoles – what become known as cytology, or present-day cell theory was established.
Developmental morphology
Until the 1860s the prevailing belief was that species remained constant through time, that each biological form was the result of an independent act of creation and therefore absolutely distinct and immutable. But the hard reality of geology and fossils needed scientific explanation. Charles Darwin’s Origin of Species (1859) replaced the assumption of constancy with the theory of descent with modification. Phylogeny became a new principle as "natural" classifications became classifications reflecting, not just similarities, but evolutionary relationships. Wilhelm Hofmeister established that there was a more or less uniform plan of organization running through all plants expressed through the alternation of generations and extensive homology of structures.[68]
Polymath German intellect Johann Goethe (1749–1832) had interests and influence that extending into botany. In Die Metamorphose der Pflanzen (1790) he provided a theory of plant morphology (he coined the word ‘’morphology’’) in which he included within “metamorphosis” modification during evolution, thus linking comparative morphology with phylogeny. Though the botanical basis of his work has been challenged there is no doubt that he stimulated discussion and research on the origin and function of floral parts.[69] His theory probably initiated the opposing views of German botanists Alexander Braun (1805–1877) and Matthias Schleiden who applied the experimental method to the principles of growth and form that were later extended by Augustin de Candolle (1778–1841).
Carbon fixation (photosynthesis)
At the start of the 19th century the notion that plants could synthesise almost all their tissues from atmospheric gases was still to be explored. Chlorophyll was named in 1818 and its chemistry gradually unraveled to be finally resolved in the early twentieth century. The mechanism of photosynthesis remained a mystery until the mid 19th century when Sachs, in 1862, noted that starch was formed in green cells only in the presence of light. It was only in 1882 that Sachs confirmed carbohydrates as the starting point for all other organic compounds in plants.[70] The connection between chlorophyll pigment and starch production was finally made in 1864 but tracing the precise biochemical pathway of starch formation did not begin until about 1915. The energy component of photosynthesis, the capture and store the Sun’s radiant energy by fixing it in carbon bonds (a process on which all life depends) was first elucidated in 1847 by Julius Rob. Mayer, but the details of how this was done would take many more years.[71]
Nitrogen fixation
Significant discoveries relating to nitrogen assimilation and metabolism, including ammonification, nitrification and nitrogen fixation (the uptake of atmospheric nitrogen by symbiotic soil microorganisms) had to wait for advances in chemistry and bacteriology in the late nineteenth century and this was followed in the early twentieth century by the elucidation of protein and amino-acid synthesis and their role in plant metabolism. With this knowledge it was then possible to outline the global nitrogen cycle.[72]
Twentieth century
Twentieth century science grew out of the solid foundations laid by the breadth of vision and detailed experimental observations of the 19th century. A vastly increased research force was now rapidly extending the horizons of botanical knowledge at all levels of plant organization from molecules to global plant ecology. There was now an awareness of the unity of biological structure and function at the cellular and biochemical levels of organisation. Botanical advance was closely associated with advances in physics and chemistry with the greatest advances in the 20th century mainly relating to the penetration of molecular organization.[73] However, at the level of plant communities it would take until mid century to consolidate work on ecology and population genetics.[74]
Research funding was now available from agriculture and industry.
By 1910 experiments using labelled isotopes were being used to elucidate plant biochemical pathways, to open the line of research leading to gene technology.
Molecules
In 1903 Chlorophylls a and b were separated by chromatography and through the 1920s and 1930s biochemists, notably Hans Krebs (1900-1981) and Carl (1896–1984) and Gerty Cori (1896–1957) began tracing out the central metabolic pathways of life and between the 1930s and 1950s the role of ATP as the chemical energy source in the cell located in mitochondria was established. From the 1930s the detail of the constituent reactions of photosynthesis were progressively revealed and by 1944 DNA had been extracted.[75]
Another remarkable discovery was that of plant hormones or “growth substances”, notably auxins, (1934) gibberellins (1934) and cytokinins (1964).[76] as well as photoperiodism (control of plant processes, especially flowering, by relative lengths of day and night).[77]
Following the establishment of Mendel’s laws, the gene-chromosome theory of heredity culminated with the work of August Weismann who identified the chromosomes of the nucleus as the hereditary material and noted the halving of the chromosome number in germ cells, anticipating the details of meiosis In the 1920s and 1930s population genetics, unified the idea of evolution by natural selection with Mendelian genetics producing the modern synthesis. By the mid-1960s the molecular basis of metabolism and reproduction was sound and the new science of molecular biology thriving. Genetic engineering, the insertion of genes into a host cell for cloning, began in the 1970s with the invention of recombinant DNA techniques and commercial applications followed in the 1990s especially in relation to agricultural crops. There was now the potential to identify organisms by molecular “fingerprinting” and to estimate the times of evolutionary change based on “molecular clocks”.
Computers, electron microscopes and evolution
In 1936 Alexander Oparin (1894–1980) had demonstrated a possible mechanism for the synthesis of organic matter from inorganic. In the 1960s it was found that the Earth’s first plants, the cyanobacteria called stromatolites, dated back some 3.5 billion years.[78]
Mid-century transmission and scanning electron microscopy presented another level of resolution to the structure of matter, taking anatomy into the new world of “ultrastructure”.[79]
As knowledge accumulated so revised classification systems of the plant kingdom were produced, perhaps the most notable being the new “phylogenetic” systems of August Eichler (1839–1887), the massive 23 volume Die natürlichen Pflanzenfamilien (The natural plant families) of Adolf Engler (1844–1930) & Karl Prantl (1849–1893) published between 1887 and 1915. Taxonomy using mostly floral characters was now being supplemented by new techniques adding characters revealed by pollen morphology, embryology, anatomy, cytology, serology, macromolecules and more.[80] Increasing computer power facilitated the development of numerical taxonomy (also called taximetrics or phenetics) for the rapid analysis of large data sets. The desire to create truly natural phylogenies spawned the disciplines of cladistics and phylogenetic systematics. The grand synthesis An Integrated System of Classification of Flowering Plants (1981) of American Arthur Cronquist (1919–1992) was soon superseded when, in 1998, the Angiosperm Phylogeny Group published a phylogeny of flowering plants based on an analysis of DNA sequences using techniques now known as molecular systematics. Molecular systematics has helped resolve questions concerning the earliest branches in the genealogy of the angiosperms (flowering plants) but it is used throughout biology. The exact relationship of fungi to plants had for some time been uncertain. Several lines of evidence pointed to fungi being different from plants, animals and bacteria – indeed, more closely related to animals than plants. In the 1980s-90s molecular analysis revealed an evolutionary divergence of fungi from other organisms about 1 billion years ago – sufficient reason to erect a unique kingdom separate from plants.[81]
Biogeography and ecology
The publication of Alfred Wegener's (1880– 1930) theory of continental drift 1912 gave additional impetus to comparative physiology and the study of biogeography while ecology in the 1930s contributed the important ideas of plant community, succession, community change, and energy flows.[82] Ecology became an independent discipline in the 1940s and 1950s after Eugene Odum (1913–2002) synthesized many of the concepts of ecosystem ecology, placing relationships between groups of organisms (especially material and energy relationships) at the center of the field. Nikolai Vavilov (1887–1943) from 1914 to 1940 produced accounts of the geography, centres of origin, and evolutionary history of economic plants that built on the extensive earlier work of Alphonse de Candolle.[83]
The cytological basis of the gene-chromosome theory of heredity extended from about 1900–1944 and was initiated by the rediscovery of Gregor Mendel's (1822–1884) laws of plant heredity first published in 1866 in Experiments on Plant Hybridization and based on cultivated pea, Pisum sativum: this heralded the opening up of plant genetics. The cytological basis for gene-chromosome theory was explored through the role of polyploidy and hybridization in speciation and it was becoming better understood that interbreeding populations were the unit of adaptive change in biology.[84]
Twenty-first century
Research is endless as for every question answered many more are revealed. Nevertheless, at the start of the 21st century in reviewing the sweep of botanical history we see that, through the power of the scientific method, most of the basic questions concerning the operations of plants have, in principle, been resolved. Now the distinction between pure and applied botany becomes blurred as our historically accumulated botanical wisdom of all levels of plant organisation is needed (but especially at the molecular and global levels) to help improve our custodianship of planet earth. Major unanswered questions now relate to the role of plants in the global cycling of life's basic ingredients: energy, carbon, hydrogen, oxygen, and nitrogen, and ways that our stewardship of plants can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change and sustainability.[85]
See also
- History of plant systematics
- History of phycology
- List of botanists
- List of botanists by author abbreviation
References
- ^ Morton 1981, p. 49
- ^ Sachs 1890, p. v
- ^ Walters 1981, p. 3
- ^ See Stearn 1986
- ^ Stearn 1965, pp. 279–91, 322–41
- ^ Reed 1942, p. 3
- ^ Morton 1981, p. 5
- ^ Reed 1942, pp. 7–29
- ^ Morton 1981, p. 15
- ^ Morton 1981, p. 23
- ^ Morton 1981, pp. 29–43
- ^ Reed 1942, p. 34
- ^ Singer 1923, p. 98
- ^ Morton 1981, p. 42
- ^ Reed 1942, p. 37
- ^ See Thanos 2005
- ^ Morton 1981, pp. 36–43
- ^ Harvey-Gibson 1919, p. 9
- ^ Singer 1923, p. 101
- ^ Morton 1981, p. 68
- ^ Morton 1981, p. 69
- ^ Morton 1981, pp. 70–1
- ^ See Sengbusch
- ^ Fahd et al 1996, p. 815
- ^ a b Morton 1981, p. 82
- ^ Boulanger 2002
- ^ Morton 1981, p. 94
- ^ Ancient Indian Botany and TaxonomyRetrieved: 2009-12-15.
- ^ Majumdar 1982, pp. 356-411
- ^ Sachs 1890, p. 19
- ^ a b Reed 1942, p. 65
- ^ Reed 1942, p. 68
- ^ Arber, pp. 146–246
- ^ Henrey 1975, pp. 631–46
- ^ Sachs 1890, p. 18
- ^ Morton 1981, pp. 121–4
- ^ Arber 1986, p. 270
- ^ Morton 1981, pp. 178–80
- ^ Reed 1942, pp. 110–1
- ^ Woodland 1991, pp. 372–408
- ^ Reed 1942, pp. 71–3
- ^ Morton 1981, pp. 130–40
- ^ Morton 1981, pp. 147–8
- ^ Reed 1942, pp. 82–3
- ^ Morton 1981, pp. 196–216
- ^ Woodland 1991, pp. 372–375
- ^ Reed 1942, p. 102
- ^ Morton 1981, pp. 301–11
- ^ Reed 1942, pp. 88–9
- ^ Reed 1942, p. 91
- ^ Morton 1981, p. 250
- ^ Reed 1942, p. 107
- ^ Morton 1981, p. 338
- ^ Reed 1942, p. 138
- ^ Reed 1942, p. 140
- ^ Reed 1942, p. 96
- ^ Reed 1942, p. 97
- ^ Reed 1942, p. 98
- ^ Reynolds Green 1909, p. 502
- ^ Morton 1981, p. 377
- ^ a b Morton 1981, p. 388
- ^ Morton 1981, p. 372
- ^ Reed 1942, pp. 126–33
- ^ Morton 1981, pp. 390–1
- ^ Morton 1981, pp. 381–2
- ^ Reed 1942, pp. 154–75
- ^ Winterborne 2005, p. 9
- ^ Reynolds Green 1909, pp. 7–10, 501
- ^ Morton 1981, pp. 343–6
- ^ Reed 1942, p. 197
- ^ Reed 1942, p. 207
- ^ Reed 1942, pp. 214–40
- ^ Morton 1981, p. 448
- ^ Morton 1981, p. 451
- ^ Morton 1981, p. 460
- ^ Morton 1981, p. 461
- ^ Morton 1981, p. 464
- ^ Morton 1981, p. 454
- ^ Morton 1981, p. 459
- ^ Morton 1981, p. 456
- ^ See Bruns 2006
- ^ Morton 1981, p. 457
- ^ See de Candolle 2006
- ^ Morton 1981, p. 453
- ^ Botanical Society of America
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- Boulanger, Diane (2002). "The Islamic Contribution to Science, Mathematics and Technology". OISE Papers in STSE Education 3.
- Bruns, Tom (2006). "Evolutionary biology: a kingdom revised". Nature 443: 758–61.
- de Candolle, Alphonse (2006). Origin of Cultivated Plants. Glacier National Park Montana: Kessinger Publishing. ISBN 9781428609464. http://books.google.com.au/books?id=a242a8XfLycC&dq=de+candolle+origin+of+cultivated+plants&printsec=frontcover&source=bl&ots=J0QV6_b_3-&sig=n1j680RUvV0lEw1yanCJF_7TMQM&hl=en&ei=dggSS9GlIpS2sgOQ9_CtCw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAoQ6AEwAA#v=onepage&q=&f=false. Retrieved 2009-12-14. (First edition in French published in 1882.)
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- Winterborne, Jeffrey (2005). Hydroponics: indoor horticulture. Guildford: Pukka Press. ISBN 9780955011207. http://www.hydroponicist.com/. Retrieved 2009-12-14.
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Further reading
- Johnson, Dale E. (1985). "Literature on the history of botany and botanic gardens 1730–1840: A bibliography". Huntia 6(1): 1–121.
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