Botany, branch of biology concerned with the study of plants (kingdom Plantae; see Plant). Plants are now defined as multicellular organisms that carry out photosynthesis. Organisms that had previously been called plants, however, such as bacteria, algae, and fungi, continue to be the province of botany, because of their historical connection with the discipline and their many similarities to true plants, and because of the practicality of not fragmenting the study of organisms into too many separate fields.
The Greeks believed that plants derived their nourishment from the soil only. Not until the 17th century did the Belgian scientist Jan Baptista van Helmont show that, although only water was added to a potted willow, it gained nearly 75 kg (165 lb), whereas the soil it stood in lost only about 60 g (about 2 oz) of weight over a period of five years. This demonstrated that the soil contributes very little to the increase in the weight of plants. In the 18th century the English chemist Joseph Priestley demonstrated that growing plants “restore” air from which the oxygen has been removed (by the burning of candles or the breathing of animals), and the Dutch physiologist Jan Ingenhousz (1730-99) extended this observation by showing that light is required for plants to restore air. These and other discoveries formed the basis for modern plant physiology, that branch of botany dealing with basic plant functions.
That water moves upward through the wood and that solutes move downward through the stems of plants was discovered independently in the 17th century by Marcello Malpighi in
Italy and Nehemiah Grew in . These facts have now been known for some 300 years, but only in the last few years have acceptable theories explaining the movements of liquids in plants been developed, using a variety of refined analytical techniques. England
Gross observations and experiments on photosynthesis and the movement of water in plants can be made without knowledge of their structure, but explanations of these phenomena require knowledge of morphology—the study and interpretation of plant form, development, and life histories—and of anatomy—the study of plant tissues and their origin and relations to one another. The cellular nature of plants was first pointed out by the English scientist Robert Hooke in the 17th century, when he observed that cork bark consists of cells. In 1838 the German botanist Matthias Schleiden proposed that all plant tissues consist of cells; this implied a basic sameness of living things and laid the foundation for the development of cytology, the study of the structure and function of cells as individual units rather than as aggegrate tissue. The German pathologist Rudolf Virchow showed in 1858 that cells are derived from preexisting cells, and thus that a continuity exists between past and present living things.
Botany does not depend on the fossil record for information concerning evolution and classification as much as does zoology, because the record for plants is much less complete than that for animals. Nevertheless, paleobotany, the study of fossil plants, has contributed greatly to the overall understanding of the evolution of the major groups of plants and especially to understanding of the interrelationships among the classes of seed plants. But much remains to be learned before fundamental questions such as the origin of the flowering plants (see Angiosperm) can be answered.
Botanists—those engaged in the study of plants—occupy themselves with a broad range of activities. Many botanists are in academic positions that involve both teaching and research duties. The latter may involve laboratory work or field studies. Strictly speaking, botany is a pure science concerned with investigating the basic nature of plants. Many aspects of botany, however, have direct importance to human welfare and advancement, and applied botany is an important field. Such fields as forestry and horticulture are closely tied to basic botanical studies, whereas those such as pharmacology and agronomy are not as closely related but still depend on basic botanical knowledge.