Marchantia Polymorpha Descriptive Essay

Marchantia, genus of liverworts (creeping ribbonlike plants) in the order Marchantiales, commonly found on moist clay or silty soils, especially on recently burned land throughout the Northern Hemisphere. Marchantia polymorpha, a well-known species, often is discussed as a representative liverwort in biology textbooks. Dark green Marchantia gametophytes (sexual plants) are branched and ribbonlike, about 1.3 cm (0.5 inch) wide and 5 to 13 cm long. The diamond-shaped markings on their upper surfaces, signs of interior air chambers, have a central pore through which air diffuses.

Male and female plants have umbrella-like, stalked reproductive structures. The male structures are disk-shaped with scalloped edges; the female structures have nine fingerlike projections. Sperm produced by male plants are splashed by raindrops onto female plants. Sporophytes (asexual plants) develop from fertilized eggs in the female structures. Vegetative reproduction occurs in both male and female plants by means of rounded, fringed gemmae (asexual buds) or by pieces of the plant body that may break off and grow.

Abstract

While written accounts of plants date back thousands of years, due to the degradation of scientific literature during the dark ages descriptions descended from Greek writings are sometimes equivocal as to species identity. Such is the case with Marchantia in the pre-Renaissance literature; however, indisputable illustrations of Marchantia polymorpha were made as early as the mid-15th century, beginning a rich historical literature on its taxonomy, development and physiology. In this review, I present three vignettes, each of which are themselves abbreviated due to space constraints. The first presents the role of Marchantia and related liverwort species in the discovery of sex in cryptogams, from the elucidation of liverwort life cycles the 18th century to the sequence of the Y chromosome in the 21st. A second vignette describes the use of M. polymorpha as a model organism in the early 19th century debate concerning the cellular nature of organisms and the origin of new cells—an endeavor that provided us with Charles-François Brisseau de Mirbel’s mémoire containing beautiful, if slightly fanciful, illustrations of the Marchantia life cycle. The final vignette chronicles the use of M. polymorpha gemmae over the past two centuries to elucidate the mechanism by which a dorsiventral body plan is established from an initially apolar gemma. While only covering a fraction of the literature available, these vignettes provide a glimpse of historical and recent discoveries available upon which to build a molecular genetic and genomic understanding of Marchantia .

Early Descriptions of Liverworts

While man’s initial knowledge of plants pre-dates the dawn of our species, the seeds of scientific investigation began in the 6th to 4th centuries BC in Greece with Ionian philosophers who based their ideas on observation and attempted to explain the world as a rational result of natural forces, a significant departure from invoking the supernatural ( Morton 1981 ). In the botanical realm this included lists of plants and their uses. One of the earliest known lists was assembled by Diokles of Karystos in about 350 BC and is thought to have consisted of a compendium of plants followed by a description of their habitats and medicinal uses ( Singer 1927 ). While all original accounts of these early writings have been lost, later authors, from the ancient Greeks through the Renaissance, continued this format referred to as a Herbal ( Arber 1912 ). The historical representations of liverworts begin with nebulous descriptions and illustrations from antiquity through the dark ages, only becoming realistic enough to be assigned unambiguously to specific species in the Renaissance. While the majority of this review is focused on the genus Marchantia , other liverwort taxa are mentioned and their phylogenetic relationships with Marchantia are depicted in Fig. 1 .

Greek and Roman antiquity

Theophrastus, a native of the island of Lesbos, is considered the ‘father of botany’, but it is probable at least some of Theophrastus’ writings were derived from or influenced by those of Diokles ( Morton 1981 ). His botanical works—the Historia Plantarum (Enquiry into Plants) and Causae Plantarum (Causes of Plants) —contain both notes on plant growth and physiology and descriptions of many plant species, native and foreign, with many of the latter being brought back to Greece during the conquests of Alexander the Great (356–323 BC) ( Scarborough 1978 , Morton 1981 ). This influx of foreign plants, animals and ideas undoubtedly broadened the scope and thinking of biology in Greece at this time.

Lichen (λειχήν) is a word of Greek origin used by Theophrastus in De Causis Plantarum (Book V 9.10) to signify a superficial growth on the bark of olive trees ( Smith 1921 ). It is suggested that the term lichen comes from the Greek ‘to lick’, as the plants ‘lick’ the bark and stones. While Theophrastus’ original use probably referred to an organism that today we would recognize as a lichen, it is assumed by Lindberg ( Lindberg 1877 ) that the term λειχήν was more broadly applied to many plants with a thalloid body plan, including liverworts. Thus, in early texts and floras based on the work of Theophrastus and other Greek and Roman authors who followed, liverworts and hornworts are referred to as Lichens.

While Theophrastus’ work was not a herbal, it provided the basis for later works, such as that of Krateus, the medical attendant of Mithridates, who produced both a written Herbal and a second novel one in which plants were depicted in figures rather than described in words, making Krateus the father of plant illustration ( Pliny and Holland 1634 ). Krateus’ illustrated format of herbal was followed for the next 1,500, years with the most influential herbal being that of Pedanius Dioscorides of Anazarba, a Greek physician and botanist who wrote a five volume encyclopedia on herbal medicine, Peri Hules Iatrikes , or De Materia Medica in its Latin translation ( Stannard 1965 , Stannard 1999 ). Undoubtedly Dioscorides based his work on those of his predecessors, including Theophrastus, Krateus and Nicander of Colophon, and it remains the primary historical source of medicines used by the ancient Greeks and through De Materia Medica and its successors, botany and medicine would be closely entwined until the beginning of the 19th century. De Materia Medica was not originally illustrated, and was copied through the centuries, first in Greek then translated into Latin and Arabic during the dark ages. During this time, illustrations were added and changes accumulated through the centuries via errors introduced by transcribers who had little, if any, knowledge of the plants described. The oldest surviving version of De Materia Medica is contained within the Juliana Anicia Codex (also known as the Codex Vindobonensis or the Vienna Dioscorides ), which was completed in Constantinople around 512 (Dioscorides 512). While the illustrations of the Juliana Anicia Codex vary in quality, the best are naturalistic, probably copied from earlier Greek texts that no longer exist, since by this time in the dark ages naturalistic drawing was a lost art. Lichen is described and illustrated in Chapter 53 of Book IV (fol. 216v.), with the following text from John Goodyer’s translation of De Materia Medica into English, a task he completed in 1655, but which was not published until the 20th century ( Dioscorides et al. 1933 ):

4.53 Leichen, Lichen

Lichen, that which grows upon rocks, but some call it Bryon, is a moss sticking to moist rocks. This being laid on doth stop ye fluxes of blood, & it doth help the Ictericall [jaundice] being laid on with honey, and doth help also the rhumes of ye mouth, & ye tongue .’

Many subsequent authors assumed that the description was of a liverwort, specifically Marchantia as it is the most common liverwort in human disturbed habitats in Europe. While the text of Dioscorides could be describing a liverwort, the accompanying illustration, where a nondescript patch of green plants is growing on top of a pile of stones, could be depicting either a true lichen or a liverwort, but more closely resembling the former. While the texts of different translations of De Materia Medica did not change much for the next millenium, the words being slavishly copied over the centuries, the illustrations, initially based on drawing from nature, degraded into unrecognizable sketches impossible to reconcile with actual plants they were supposed to represent ( Sachs 1890 , Morton 1981 ).

While Dioscorides’ description is ambiguous, that of Pliny is more readily interpreted as a marchantialean liverwort. Pliny the Elder (23–79 AD) was a Roman naturalist, author and military commander in the early Roman Empire. His Naturalis Historia is a 37 volume encyclopedia of the knowledge of his time, completed in 77 AD, 2 years before his death in an ill-fated attempt to rescue friends in Herculaneum from the eruption of Mt Vesuvius. While Pliny and Dioscorides wrote contemporaneously they were unlikely to have been aware of each other’s works. The relevant passage in Naturalis Historia is in Book XXVI, where Lichen is described in Chapter IIII from Philemon Holland’s English translation ( Pliny and Holland 1634 ):

… but the hearbe Liverwort excellent all the rest, which therupon tooke the name Lichen: it groweth upon stonie grounds, with broad leaves beneath about the root, having one stalke and the same small, at which there hang downe long leaves; and surely this a proper hearbe also to wipe away all markes and cicatrices in the skin, it is be bruised and laid upon them with honey: Another kind of Lichen or Liverwort there is, cleaving wholly fast upon rocks and stones in a manner of mosse, which also is singular for those tettars, beeing reduced into a liniment. This hearbe likewise stauncheth the flux of bloud in greene wounds, if the juice be dropped into them: and in a liniment, it serveth well to be applied unto apostumat places: the jaundise it healeth, in case of the mouth and tongue be rubbed and annointed with it and hony together: but in this cure the patients must have in charge, To bath in salt water, to annoint themselves with the oile of almonds, and in any case to abstaine from all salads and pothearbs of the garden .’

Based on his use of the term, it can be assumed that Holland accepted that the plant described by Dioscorides and Pliny was a liverwort.

The Renaissance

As stated by Sachs ( Sachs 1890 ) ‘ … the botanical literature of the middle ages grows less and less valuable … as they are deficient in ideas … [and] had sunk so low, that not only were the figures embellished with fabulous additions … sometimes drawn purely from fancy, but the meagre descriptions of quite common plants were not taken from nature, but borrowed from earlier authorities and eked out with superstitious fictions. ’ At the advent of the Renaissance this began to change, first in northern Italy and subsequently spreading to the remainder of Europe ( Sprague and Nelmes 1931 , Morton 1981 ). The unprecedented wealth of merchants and bankers from the commercial cities of Venice, Florence, Genoa and Milan led to considerable political power and independence, which was used to support cultural change and scientific inquiry. The wealth was in part derived from these city states controlling trade routes, which also brought knowledge of an unparalleled number of new plant species. At Padua, and then elsewhere, the establishment of positions within Italian universities to study botany explicitly, and the universities’ independence from the influence of the Church, allowed botanical studies to flourish. By 1546 botanical gardens were established in Pisa, Padua and Florence, a trend that spread across Italy and then more broadly in Europe. It is not surprising that the early botanical Renaissance occurred around Padua given the relationship of botany to medicine and the blossoming of medical schools at this time in northern Italy.

The earliest known illustration that is undoubtedly Marchantia polymorpha can be found in a copy of Libre de Simplicibus , known as Marciana Codex lat. VI 59 , which was compiled by Italian physician Benedetto Rinio in 1419, and illustrated by an otherwise unknown artist, Andrea Amadio ( Blunt and Raphael 1994 , Pächt 1950 ). In Marciana Codex lat. VI 59 , naturalistic illustrations of plants are presented along with their names in Greek, Arabic, Latin and other languages. While the text was compiled in 1419, the illustrations may not have been completed until the mid-15th century, as the manuscript is dated 1445–1448.

The advent of the printing press facilitated a demand for widely available books, and in the first half of the 16th century after the Renaissance had spread northward, three German botanists, Otto Brunfels, Leonhart Fuchs and Jerome Hieronymus Bock, produced Herbals. In these they provided both figures and descriptions often based on their own observations of local plants, although they still primarily focused on plants ‘useful’ to man. In Fuchs’ De Historia Stirpium, first published in 1542, is the first conclusive depiction of M. polymorpha (female) in printed literature [ Fig. 2 ; ( Fuchs et al. 1542 )]. Fuchs had previously chastised earlier authors for changing the name from Lichen to Hepatica when he can find no evidence in the writings of the Greeks of Lichen as a treatment for liver ailments, but rather all the Greek descriptions are of using extracts of Lichen as a topical ointment.

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