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Agriculture LibreTexts

1: Introduction to Botany

What is Botany?

Botany is one of the main branches of Biology (zoology being the other); it is the systematic and scientific study of plants. Botany covers a lot of scientific discipline, such as chemistry, pathology, microbiology etc. Botany also covers specific sciences that caters for a specific study area in plant life such as Photochemistry that deals with chemical reaction, product and chemical derivatives in plants as well as it effects on other biological species, Plant Anatomy and Morphology which deals with structures, evolution, process and mechanism of plant parts and Taxonomy which is the science of describing, naming, and classifying of organisms. New sciences such as Genetic Engineering which caters the issue of Genetically Modified Organism (GMO), Economic Botany which deals on how to utilize the plant kingdom and even Forensic Botany, that uses plant to find clues for crimes.

Since the core of botany is plants (though it should also be reminded that in the study of botany, Kingdom Fungi and Algae is also discussed, though it has its own study: Mycology often paired with Virology, Phycology for algae). Basic Introductory Botany course will enable you to understand the interesting mechanisms of plants which include their growth and development, chemical properties, genetics, ecology, evolution etc. and most of them will instill an understanding on the importance of plants.


What is a plant?

Anyone can tell which is a plant and an animal; your dog looks very different from your tomato plant or your mom's roses. Plants don't often get as much appreciation as animals; there are more people interested in zoos' than gardens, and often times the real entity of plant is often boxed as either: good for "food or flower" thinking. Plants are exciting and interesting than anyone can expect; diversity of plant life ranges from carnivorous Nepenthes sp (Pitcher plant), giant stinking Rafflesia, beautiful orchids, to the towering and old Sequoia.

A. IMPORTANCE OF PLANTS: To appreciate this course, one must understand the need for studying plants specifically their importance. Before tackling the technicalities of plants the following are some of the importance of plants:

Oxygen: In the process of photosynthesis plants give off oxygen as a byproduct of the reaction. Oxygen is essential for our respiratory process.

Human Nutrition - Virtually all foods eaten come from plants, either directly from staple foods and other fruit and vegetables, or indirectly through livestock or other animals, which rely on plants for their nutrition. Plants are the fundamental base of nearly all food chains because they use the energy from the sun and nutrients from the soil and atmosphere and convert them into a form that can be consumed and utilized by animals; this is what ecologists call the first trophic level. Botanists (scientist who specialize in Botany) also study how plants produce food we can eat and how to increase yields and therefore their work is important in mankind's ability to feed the world and provide food security for future generations, for example through plant breeding. Botanists also study weeds, undesirable plant, especially ones that grow profusely where they are not wanted. Weeds are a considerable problem in agriculture, and botany provides some of the basic science used to understand how to minimize 'weed' impact in agriculture and native ecosystems ( Examples of Staple plant food are: Oryza sativa (rice), Zea mays (maize), Solanum tuberosum (potatoes), Triticum sp (wheat). There are thousands of list of edible plants, from the nori of Japan which are algae, to pine nuts.

Source of Medicine - Plants have been a main source of medicine as well as for research. Plants played an important role specially, in ancient civilization and tribes, on which plants has been used to treat illness, some of these plants made it into mainstream and a key ingredient in some essential medicine.

Examples are: Digitalis purpurea - purple foxglove on which a chemical called digitalin, a cardiac glycoside can be extracted is a cardio tonic that helps to control heart rate.

Cinchona tree - an essential discovery for the extract of quinine an anti malaria drug agent. Quinine was the first effective treatment for malaria caused by P falciparum, appearing in therapeutics in the 17th century. It remained the antimalarial drug of choice until the 1940s, when other drugs took over. Since then, many effective antimalarials have been introduced, although quinine is still used to treat the disease in certain critical situations.

It should also be noted that chemical from plants also have its pros and cons, pros for its use in research and medicine, but there are plants that can have ill effect on both animals and plants such as the infamous Conium maculatum (poison hemlock) that killed Socrates, Cannabis sativa (marijuana), Papaver sominiferum (opium), Erythroxylum coca (cocaine) which have addictive properties, and may cause detrimental ill effect on human.

History and Development of Botany

The study of Botany has its long history, Ancient civilizations have known to use plants in many aspects, much of it is for food, thus domestication and agriculture took place. The Chinese had the rice, Andes potatoes, American Indians Corn and many more.

Among the earliest of botanical works, written around 300 B.C., are two large treatises by Theophrastus: On the History of Plants (Historia Plantarum) and On the Causes of Plants. Together these books constitute the most important contribution to Botanical Science during antiquity and on into the Middle Ages. The Roman medical writer Dioscorides provides important evidence on Greek and Roman knowledge of medicinal plants.

In ancient China, the recorded listing of different plants and herb concoctions for pharmaceutical purposes spans back to at least the Warring States (481 BC-221 BC). Many Chinese writers over the centuries contributed to the written knowledge of herbal pharmaceutics. There was the Han Dynasty (202 BC-220 AD) written work of the Huangdi Neijing and the famous pharmacologist Zhang Zhongjing of the 2nd century. There were also the 11th century scientists and statesmen Su Song and Shen Kuo, who compiled treatises on herbal medicine and included the use of mineralogy.

Important medieval works of plant physiology in India include the Prthviniraparyam of Udayana, Nyayavindutika of Dharmottara, Saddarsana-samuccaya of Gunaratna, and Upaskara of Sankaramisra. [3]

In 1665, using an early microscope, Robert Hooke discovered cells in cork, and a short time later in living plant tissue. The German Leonhart Fuchs, the Swiss Conrad von Gesner, and the British authors Nicholas Culpeper and John Gerard published herbals that gave information on the medicinal uses of plants.

In 1754 Carl von Linné (Carl Linnaeus) divided the plant Kingdom into 25 classes. One, the Cryptogamia, included all the plants with concealed reproductive parts (algae, fungi, mosses and liverworts and ferns).

Modern Botany

A considerable amount of new knowledge today is being generated from studying model plants like Arabidopsis thaliana. This weedy species in the mustard family was one of the first plants to have its genome sequenced. The sequencing of the rice (Oryza sativa) genome and a large international research community have made rice the de facto cereal/grass/monocot (a plant having a single cotyledon) in the seed model. Another grass species, Brachypodium distachyon is also emerging as an experimental model for understanding the genetic, cellular and molecular biology of temperate grasses. Other commercially-important staple foods like wheat, maize, barley, rye, pearl millet and soybean are also sequenced. Some of these are challenging to sequence because they have more than two haploid (n) sets of chromosomes, a condition known as polyploidy, common in the plant kingdom. Chlamydomonas reinhardtii (a single-celled, green alga) is another plant model organism that has been extensively studied and provided important insights into cell biology.

In 1998 the Angiosperm Phylogeny Group published a phylogeny of flowering plants based on an analysis of DNA sequences from most families of flowering plants. As a result of this work, major questions such as which families represent the earliest branches in the genealogy of angiosperms are now understood. Investigating how plant species are related to each other allows botanists to better understand the process of evolution in plants.