BOTONY

BOTONY AT A GLANCE

                         BOTONY  the  branch of biology that deals with plants. It involves the study of the structure, properties, and biochemical processes of all forms of plant life, including trees.  Also included  within its scope are plant classification and the study of plant  diseases  and  of  the  interactions of plants with their physical environment. Over the years various specialized branches of botany have developed, and  the  principles  and  findings  of botany, moreover, have provided the base on which depend such applied plant sciences as agriculture, horticulture, and forestry. The  science of botany traces back to the ancient Greco-Roman  world  but  received its  modern  impetus  in  Europe  in  the 16th century, mainly through the work of various physicians  and  herbalists.  These  professionals,  in  seeking  plants  useful  in  medicine,  began  seriously  to  observe plants themselves, as reflected in the woodcuts  with  which their herbal books were illustrated. In the 17th century, as a result of the earlier  revival  of  learning  and  of  increased  facilities  for  travel  and study in Europe and Asia, many more plants became known, and some botanists turned from medical botany to attempts to name and catalog all known kinds of plants. The most celebrated early work of this kind was Pinax theatri botanici (1623; "Illustrated Exposition of Plants")  by  the  Swiss scientist Gaspard Bauhin, who listed  and  described  about  6,000  species.  In  the  18th  century the greatest figure in botany was the Swedish scientist CarolusLinnaeus.His most valuable and lasting contributions were his careful descriptions of approximately 6,000 species arranged in genera (the same arrangement used today), his collation of the species that he knew with the names and descriptions of previous botanists, and his rules of nomenclature. He established binomial nomenclature--i.e., the naming of each  species  by  two words, of  which  the first is the name of the genus to which it belongs and the second is a qualifying word,  usually  an  adjective  (e.g., the dog rose is Rosa canina). Even in  this early period,  botany  was becoming specialized. While many botanists were occupied only with the classes and names of plants, the foundations of anatomy, morphology, and physiology were being laid.  The important field of genetics was initiated in the 19th century, principally through the work of the Austrian botanist Gregor Mendel.

                         Today  the  principal  branches of botanical study are morphology, physiology, ecology, and systematics (the identification  and  ranking  of  all plants).     Various  subdisciplines  include  bryology  (the study of mosses and liverworts), pteridology (the study of ferns and their relatives), paleobotany  (the study  of  fossil  plants),  and  palynology ( the study of modern and fossil pollen and spores). Methods in botany Morphological aspects The invention of the compound microscope provided a valuable and durable instrument for the investigation of the inner structure of plants.  Early  plant morphologists, especially  those  studying  cell structure,  were  handicapped  as  much by the lack of adequate knowledge of how to prepare specimens as they were by the imperfect microscopes of the time. A revolution in the effectiveness of microscopy occurred in the second half of the 19th century with the introduction of techniques for fixing cells and for staining their component parts. Before  the  development  of  these  techniques,  the cell,  viewed with the microscope, appeared as a minute container with a dense portion called the nucleus.  The discovery that parts of the cell respond to certain stains made observation easier.  The development of techniques for preparing tissues of plants for microscopic examination was continued in the 1870s and 1880s and  resulted  in  the gradual  refinement  of  the field  of  nuclear cytology, or karyology. Chromosomes were recognized as constant  structures  in  the  life  cycle  of  cells,  and  the  nature and  meaning  of meiosis, a type of cell division in which the daughter cells have half the number of chromosomes of the parent, was discovered; without this discovery, the significance of Mendel's laws of heredity might have gone unrecognized. Vital stains, dyes that can be used on living material, were first used in 1886 and  have been greatly refined since then. Improvement of the methodology of morphology has not been particularly rapid, even though satisfactory techniques  for  histology,  anatomy, and  cytology  have  been developed. The embedding of material  in  paraffin  wax, the  development  of  the  rotary  microtome for slicing very thin sections of tissue for microscope viewing, and the development of stain techniques are refinements of previously known  methods.  The  invention of the phase  microscope  made  possible the  study  of  unfixed  and  unstained  living  material-- hopefully  nearer  its  natural state.  The development   of   the  electron  microscope,  however,  has  provided   the plant   morphologist  with  a  new  dimension  of magnification of  the  structure  of plant  cells  and  tissues.  The  fine structure  of  the  cell  and  of its components, such as mitochondria and the Golgi apparatus, have come under intensive study.

                                 Knowledge  of  the  fine  structure  of  plant  cells  has  enabled investigators  to  determine the sites of important biochemical activities, especially those involved in the transfer  of  energy  during photosynthesis and respiration. The scanning electron microscope, a relatively recent development, provides a three-dimensional image of surface structures at very great magnifications.  For experimental  research on the morphogenesis of plants, isolated organs in their embryonic stage, clumps of cells, or even individual cells are grown. One of the most interesting  techniques  developed thus far permits the growing of plant tissue of higher plants as single cells; aeration and continuous agitation keep the cells suspended  in the liquid culture medium.