Botany-An introduction to plant biology

(Unedited version)
Originally appeared in the December 2006 issue of
Tropical Fish Hobbyist Magazine

My column this month is a little different than usual. My original intent was to go over the basic parts of plants, and some of the botanical terms you might come across in an aquatic plant guide, including a very brief history of botany. Well as I did the research I thought the history of botany was actually pretty interesting. I was having some trouble getting it to any where near as small as a few paragraphs. My search then led me to some the current areas of research in botany. I was surprised to find it’s an exciting field right now with a lot of emphasis on aquatic plants. After struggling for some time to try to write my original column, I decided that maybe you’d find this all interesting also.

Plants vs. Animals

Plants are very different from animals. Animals are born with all their basic body parts, and after birth get larger. Plants on the other hand start out as a small seed and then develop their parts. And then they keep developing and growing more new parts.

This new growth will also adapt to its surroundings. Plants can change not only what they grow but how they grow. We see this all the time in bringing new aquarium plants home. They are often grown emersed so the leaves and stems are adapted to living in the air. When we put them our tanks those parts are no longer appropriate for the plant, so they often die and if conditions in your tank are right, new growth will appear.

And of course there’s the really big difference, plants make their own food. They use the energy from light to create food with oxygen as a bi-product. They are the autotrophs who make the food and we and all the other animals are the heterotrophs that must some how get the energy of the plants either through eating them or eating the other animals that eat the plants.

Why Are Plants Important?

Why do we study and understand something so different from ourselves? Because we need them to survive, mankind has always had interest in plants. First we learned which ones to eat, then found other uses, as medicines, dyes and to build with. Eventually we learned how to grow plants ourselves. And finally through selective cultivation we learned how to change the plants themselves to better serve our needs.

The way plants are categorized and studied today evolved as mankind learned more. The way we understand and study plants has been a gradual process, with a few periods of heightened activity. The first and most obvious ways people can study plants is how they look, and what we can observe visibly about them and that’s how people studied botany until recent history.

As human culture developed we also started to use plants for aesthetic purposes. Egyptians even recognized the beauty of aquatic plants. Their art contains many images of papyrus and lotus. They, among other ancient cultures also studied plants as food, for medical purposes and other practical uses, such as making paper. Even before the great names we now know of in botany began there work, there was general cultural knowledge of some aspects of plant life.

There are several great names in Botany as in all scientific fields, but we should also recognize that the names remembered are usually those that organized that information. They often did come up with new ideas, but just as importantly they also recorded the common knowledge about plants that was available at their time. They built on the information already learned through years of observations by people whose names we’ll never hear.

The History of Botany

The man known as the father of botany is Theophrastus, a student of Aristotle’s. Theophrastus was born about 372 BC. He went to Athens to study under Plato and there met Aristotle, became his student, and then his colleague. Aristotle found that for his own safety he may be better off leaving Athens. When he did, he gave Theophrastus his papers and left him as head of the Lyceum, the school that Aristotle had founded. Theophrastus was apparently well loved, and continued with the school and his own areas of interest. He wrote many books; among them were 2 important sets of books on plants, “Historia de Plantis” (History of Plants) and “De Causis Plantarums” (The Causes of Plants.)

Even early on plants were separated and categorized by their similar characteristics. Theophrastus understood the difference between dicots and monocots, angiosperms and gymnosperms. He categorized plants in to 4 groups; trees, shrubs, undershrubs and herbs. He also wrote on germination, distribution, cultivation, and different forms of propagation, such as with seeds and vegetatively. As people learned more about these characteristics the categories and our understanding changed.

Another important early name in botany is Pedanius Dioscorides. He was a physician who served in Emperor Nero’s army as a botanist. Dioscorides wrote a book on botany called “De Materia Medica,” about 78 AD that dealt mostly with the pharmacological uses of plants. This was the work that was the most influential until the 1600’s, and served as an important reference for later works.

During the next period of several hundred years, as the Roman Empire declined and fell, little happened in the study of plants in the western world. The ancient writings that survived did so with the Islamic people and later in monasteries.

During the late 15th and 16th centuries the study of botany once again became predominant. The works of both Theophrastus and Dioscorides were again read by the western world. The new invention of the printing press, made it possible to reprint and distribute these works to more people. Dioscorides work was published and used frequently during that time. This was also a period of great exploration which led to the discovery of many new plants, some of which were cultivated in European gardens and became new food staples to those cultures.

Many scientists, botanists and explorers contributed to the large growth in knowledge during this time. As more and more scientific knowledge became available, those studying that knowledge became more specialized, which led to further discoveries. This was an age of incredibly increasing knowledge.

In 1753 Carl Linnaeus published “Species Plantarum. “ This is easily one of the most important books ever in the field of biology. This was a little more than a hundred years before Darwin published “Origin of the Species.” The idea of evolution hadn’t yet been born, so plants were grouped according to physical similarities. We’re still using a modified version of this system to classify living things.

Linnaeus work contained the known plant species of the time. He used previous material and organized the individual plant descriptions in a uniform manner. He created a system for organizing plants in such a way that anyone could find the type of plant by physical characteristics. He grouped plants in Taxa. Though some plants were referenced as binomials in much earlier works, Linnaeus gave every plant a binomial name, and began the use of the universal binomial nomenclature also still in use today.

The next major step in our understanding of biology was through Charles Darwin in 1859. Since the acceptance of the Evolution in most scientific circles the field of taxonomy has grown to try to incorporate the evolutionary relationships of plants.

The development of the microscope was, like many things a series of incremental discoveries from ancient times. In Holland during the late 17th and early 18th century Anthony Leeuwenhoek made great advancements in the microscope. He also studied what could be seen with his new microscopes, looking in to a miniature world that had never been seen by mankind before. Leeuwenhoek is known as the Father of Microscopy. Seeing cells and internal structures of plants certainly contributed to our understanding of them. As new knowledge has been acquired the structure of the taxonomic tree has changed.

New Areas of Research

Newer discoveries in our understanding of things like proteins and DNA are even now increasing our understanding of the ancient relationships of plants. Some of the more interesting news coming out of these new areas of research is where some aquatic plants fit in the evolutionary biology of plants. By comparing differences in these levels botanists are better able to determine where different plants diverged on an evolutionary time line. The quest to discover the mysteries of the evolution of the angiosperms (flowering plants) is a hot field both for botanists and palaeobotanists.

Ceratophyllum, that very common fast growing floating plant aquatic plant keepers know as hornwort, is believed to be one of the earliest angiosperms. Ceratophyllum in particular is a puzzle. Botanists just can’t quite figure out how it’s related to the other plants. Among other aquatic plants considered to be among the early angiosperms are ancestors of the water lilies and their relatives, including other well known aquarium plants Barclaya longifolia and Cabombas.

All of the new information being discovered about both plants and animals recently is finally allowing scientists to create a system to more accurately group animals according to their evolutionary ancestors, called phylogeny. The common ancestral groups are called clades. They can also create family trees that represent the evolutionary relationships between organisms, called phylogenic trees.

How will these new discoveries affect our current system of Linnaean taxonomy? Will it stay the same or be replaced? No one can tell the future. Reading comments from scientists or talking to them can get you a different answer depending on their viewpoints, though it seems clear there will be some affects. Either way having a much stronger understanding of how the plants developed will be beneficial in our understanding of how our world works.

Questions or Comments?

If you have questions or Comments about this column, join the Natural Aquariums Forum and post them here.

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