He found that stomata were composed of pairs of cells, rather than a single cell with a hole. Anatomical studies on the stele were consolidated by Carl Sanio — who described the secondary tissues and meristem including cambium and its action. Hugo von Mohl — summarized work in anatomy leading up to in Die Vegetabilische Zelle but this work was later eclipsed by the encyclopaedic comparative anatomy of Heinrich Anton de Bary in Studies had also begun on the origins of the carpel and flower that continue to the present day.
The riddle of water and nutrient transport through the plant remained. Physiologist Von Mohl explored solute transport and the theory of water uptake by the roots using the concepts of cohesion, transpirational pull, capillarity and root pressure. There were, however, some advances elsewhere such as the early exploration of geotropism the effect of gravity on growth by Englishman Thomas Knight, and the discovery and naming of osmosis by Frenchman Henri Dutrochet — The cell nucleus was discovered by Robert Brown in Demonstration of the cellular composition of all organisms, with each cell possessing all the characteristics of life, is attributed to the combined efforts of botanist Matthias Schleiden and zoologist Theodor Schwann — in the early 19th century although Moldenhawer had already shown that plants were wholly cellular with each cell having its own wall and Julius von Sachs had shown the continuity protoplasm between cell walls.
From to it became clear that cell nuclei are never formed anew but always derived from the substance of another nucleus. In 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 found 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 of chromosomes, now known as meiosis the field of heredity was opened up. By 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.
Later, the cytological basis of the gene-chromosome theory of heredity extended from about — and was initiated by the rediscovery of Gregor Mendel 's — laws of plant heredity first published in 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.
Until the s it was believed that species had remained unchanged through time: each biological form was the result of an independent act of creation and therefore absolutely distinct and immutable. But the hard reality of geological formations and strange fossils needed scientific explanation. Charles Darwin 's Origin of Species 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 similar pattern of organization in all plants expressed through the alternation of generations and extensive homology of structures. Polymath German intellect Johann Goethe — had interests and influence that extended into botany. In Die Metamorphose der Pflanzen he provided a theory of plant morphology he coined the word "morphology" and he included within his concept of "metamorphosis" modification during evolution, thus linking comparative morphology with phylogeny.
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Though the botanical basis of his work has been challenged there is no doubt that he prompted discussion and research on the origin and function of floral parts. At the start of the 19th century the idea that plants could synthesise almost all their tissues from atmospheric gases had not yet emerged. The energy component of photosynthesis, the capture and storage of the Sun's radiant energy in carbon bonds a process on which all life depends was first elucidated in by Mayer , but the details of how this was done would take many more years.
The mechanism of photosynthesis remained a mystery until the midth century when Sachs, in , noted that starch was formed in green cells only in the presence of light and in he confirmed carbohydrates as the starting point for all other organic compounds in plants. 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 19th century and this was followed in the early 20th 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. 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.
On a more practical level research funding was now becoming available from agriculture and industry. In Chlorophylls a and b were separated by thin layer chromatography then, through the s and s, biochemists, notably Hans Krebs — and Carl — and Gerty Cori — began tracing out the central metabolic pathways of life. Between the s and s it was determined that ATP , located in mitochondria , was the source of cellular chemical energy and the constituent reactions of photosynthesis were progressively revealed. Then, in DNA was extracted for the first time.
Following the establishment of Mendel's laws, the gene-chromosome theory of heredity was confirmed by the work of August Weismann who identified chromosomes as the hereditary material.
Also, in observing the halving of the chromosome number in germ cells he anticipated work to follow on the details of meiosis , the complex process of redistribution of hereditary material that occurs in the germ cells. In the s and s population genetics combined the theory of evolution with Mendelian genetics to produce the modern synthesis. By the mids the molecular basis of metabolism and reproduction was firmly established through the new discipline of molecular biology. Genetic engineering , the insertion of genes into a host cell for cloning, began in the s with the invention of recombinant DNA techniques and its commercial applications applied to agricultural crops followed in the s.
There was now the potential to identify organisms by molecular " fingerprinting " and to estimate the times in the past when critical evolutionary changes had occurred through the use of " molecular clocks ". Increased experimental precision combined with vastly improved scientific instrumentation was opening up exciting new fields. In Alexander Oparin — demonstrated a possible mechanism for the synthesis of organic matter from inorganic molecules.
In the s it was determined that the Earth's earliest life-forms treated as plants, the cyanobacteria known as stromatolites , dated back some 3. 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 ".
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Taxonomy based on gross morphology was now being supplemented by using characters revealed by pollen morphology , embryology , anatomy , cytology , serology , macromolecules and more. The emphasis on truly natural phylogenies spawned the disciplines of cladistics and phylogenetic systematics. The grand taxonomic synthesis An Integrated System of Classification of Flowering Plants of American Arthur Cronquist — was superseded when, in , the Angiosperm Phylogeny Group published a phylogeny of flowering plants based on the analysis of DNA sequences using the techniques of the new molecular systematics which was resolving questions concerning the earliest evolutionary branches of the angiosperms flowering plants.
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 ss 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.
The publication of Alfred Wegener 's — theory of continental drift gave additional impetus to comparative physiology and the study of biogeography while ecology in the s contributed the important ideas of plant community, succession , community change, and energy flows. Building on the extensive earlier work of Alphonse de Candolle, Nikolai Vavilov — from to produced accounts of the geography, centres of origin, and evolutionary history of economic plants.
In reviewing the sweep of botanical history it is evident that, through the power of the scientific method, most of the basic questions concerning the structure and function of plants have, in principle, been resolved. Now the distinction between pure and applied botany becomes blurred as our historically accumulated botanical wisdom at all levels of plant organisation is needed but especially at the molecular and global levels to improve human custodianship of planet earth.
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The most urgent unanswered botanical questions now relate to the role of plants as primary producers in the global cycling of life's basic ingredients: energy, carbon, hydrogen, oxygen, and nitrogen, and ways that our plant stewardship can help address the global environmental issues of resource management , conservation , human food security , biologically invasive organisms , carbon sequestration , climate change , and sustainability.
From Wikipedia, the free encyclopedia. Main article: Outline of botany. Main article: Neolithic Revolution. Further information: Cultivated plant taxonomy and Herbal. Main article: Theophrastus. Main article: Roman agriculture. Further information: Herbalism , Chinese medicine , Byzantine medicine , and Islamic medicine.
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Further information: Plant sexuality and Alternation of generations. Further information: Ecology and Plant community. Further information: Plant anatomy and Cell theory. Main article: Transpiration. Main article: Cell theory. Main article: Evolution.
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Further information: Soil plant atmosphere continuum and Photosynthesis. Main article: Nitrogen fixation. Main article: Molecular biology. Further information: Ultrastructure and Palynology. Main article: Biogeography. International Botanical Congress History of plant systematics Botanical illustration History of phycology List of botanists List of botanists by author abbreviation. See also: Bibliography of botany.