botany

Herbal from Trento, Italy, from the 14th century, showing the Chavalaritas Roma plant, which was used for sutures and to stop haemorrhages. Herbals were ancient manuals to aid in the identification of plants for medicinal purposes; many manuscript herbals were published in medieval Europe, drawing largely on the herbals compiled by the ancient Greeks.

Study of living and fossil plants, including form, function, interaction with the environment, and classification.

Botany is subdivided into a number of specialized studies, such as the identification and classification of plants (taxonomy), their external formation (plant morphology), their internal arrangement (plant anatomy), their microscopic examination (plant histology), their functioning and life history (plant physiology), and their distribution over the Earth's surface in relation to their surroundings (plant ecology). Palaeobotany concerns the study of fossil plants, while economic botany deals with the utility of plants. Horticulture, agriculture, and forestry are branches of botany.

History The most ancient botanical record was carved on the walls of the temple at Karnak, Egypt, about 1500 BC. The Greeks in the 5th and 4th centuries BC used many plants for medicinal purposes, the first Greek ‘Herbal’ being drawn up about 350 BC by Diocles of Carystus. Botanical information was collected into the works of Theophrastus of Eresus (380–287 BC), a pupil of Aristotle, who founded technical plant nomenclature. Cesalpino in the 16th century sketched out a system of classification based on flowers, fruits, and seeds, while Joachim Jungius (1587–1657) used flowers only as his criterion. The English botanist John Ray (1627–1705) arranged plants systematically, based on his findings on fruit, leaf, and flower, and described about 18,600 plants.

The Swedish botanist Carl von Linné, or Linnaeus, who founded systematics in the 18th century, included in his classification all known plants and animals, giving each a binomial descriptive label. His work greatly aided the future study of plants, as botanists found that all plants could be fitted into a systematic classification based on Linnaeus' work. Linnaeus was also the first to recognize the sexual nature of flowers. This was followed up by the English naturalist Charles Darwin and others.

Later work revealed the detailed cellular structure of plant tissues and the exact nature of photosynthesis. Julius von Sachs (1832–1897) defined the function of chlorophyll and the significance of plant stomata. In the second half of the 20th century, much has been learned about cell function, repair, and growth by the hybridization of plant cells (the combination of the nucleus of one cell with the cytoplasm of another). With modern tools, such as the electron microscope, the inner structure of plant cells and the function of the intracellular organelles can be studied.

Classification The plant kingdom is very varied. Although the individual groups of plant types are fairly distinct, how the different plant types are related to each other is still debated. One common classification rather artificially divides plants into Thallophyta and Tracheophyta:

The Thallophyta include the more primitive, simpler plants, that may be unicellular or multicellular and grow to quite a size, but do not have a true stem, leaves, and root. They reproduce asexually by spores or sexually by fusion of male and female reproductive cells (gametes). The Thallophyta include: (1) bacteria, unicellular organisms without chlorophyll; (2) algae, mostly aquatic plants, ranging from unicellular forms to complex and often very large seaweeds, chlorophyll-containing; (3) fungi, plants without chlorophyll that live on dead or living organisms. Slime moulds have a motile, unicellular phase, but most fungi are made up of filaments, as can be seen on mouldy bread, with fruiting bodies (reproductive organs) that may be quite large, one example being the mushrooms; (4) lichens, algae, and fungi living together in symbiosis; (5) bryophytes, the liverworts, and mosses.

The Tracheophyta, or vascular plants, have differentiated stems, roots, and leaves, and within their stems are tubes that conduct fluids up and down the plant body. These tubes (vessels) are the xylem, which carries water and minerals from the roots, and the phloem, which carries water and sugars from the leaves. Vascular plants are divided into: Microphyllophyta or Lepidophyta, club mosses; Arthrophyta or Calamophyta, horsetails; Pteridophyta, ferns; and the seed-bearing plants, the gymnosperms and the angiosperms.

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