Lesson 2

Plants in Life and in History

Reading Assignment

Lesson 02 Commentary

Chapter 1, pp. 2-8; Chapters 11 & 12, pp. 181-196; Chapter 9, pp. 139-141, 144-155

Learning Objectives

After successfully completing this lesson, you will:

Have an understanding of the importance of plants in our world and their significance in human history.

Be able to explain the history of the domestication of plants and describe the early plant domestication centers.

Be able to explain the various types of organisms covered by this course, including angiosperms and gymnosperms and the differences between plants and fungi.

Key Terms

agriculture, archaea, angiosperm, conifer, centers of crop origin, domestication, eubacteria, eukaryotes, fibers, fungi, gymnosperm, photosynthesis and viridaeplantae

Plants

Think about your morning routine. Regardless of how you start your day—with a leisurely breakfast, a wake-up shower, a hasty cup of coffee or even if you just slap on clean clothes and fly out the door—you can be sure that each facet of your morning ritual is connected to a plant product. Plants provide people with food, clothing, shelter, products to treat diseases and more. Plants are fundamental for all life. Without plants and the photosynthetic organisms that preceded them, there would be no appreciable oxygen in the atmosphere and no life as we know it.

Sadly, in our busy lives, we seldom take a moment to appreciate the beauty of plants, yet alone to remember all the products and services they provide for us. It is easy to overlook a tree without remembering that a single tree can provide us with oxygen, shelter and shade. There is a good chance that you rarely give cotton a second thought but cotton plants are the source of fibers that make up the bulk of human clothing. The humble potato is used to make a host of products from french fries to sizing (starch added to paper to make it stiff and to enhance ink uptake). Both cotton and potatoes were important in shaping the history of the United States. Throughout this course, it is hoped that you will gain a fuller appreciation for the importance of plants in human society.

Plant domestication altered human society and shaped the world we now inhabit. For over ninety percent of the history of modern human beings, we were primarily foragers. As foragers, human cultures developed a sophisticated body of knowledge of edible and utilitarian plant species. Long before the first plant was domesticated, wild plant products including seeds, fruits and roots provided sustenance to the human race. The gradual shift to reliance on agriculture and domesticated plants began around 10,000 years ago as several human cultures independently began to cultivate domesticated plants. The centers of crop origins are spread across the globe. Archeological evidence from the Fertile Crescent (in the modern-day Middle East), the mountains of South America, the valleys of Central America and the river valleys of Asia reveals that several different grains (corn, barley, wheat and rice), tubers (both white and sweet potatoes as well as other tubers) and fruits (such as squash) were among the earliest domesticated plants. In the modern world, representatives from the earliest domesticated grains still dominate world production with rice, wheat and corn accounting for over 60% of the world’s agricultural production. Domestication of plants was a gradual process. Over 3000 years passed before modern bread wheat evolved via artificial selection by humans from its ancestral relative, einkorn wheat. Modern crops such as corn bear little resemblance to their wild relatives. They have been shaped through selection by humans to fit our needs.

The Domestication of Plants

Agriculture and the societal changes that go along with a settled agrarian community spread throughout the world. "Why agriculture?" is not an easy question to answer. It is important to remember that though most cultures can trace their beginnings to early agricultural societies, a few foraging societies still persist today. Rather than fixating on who domesticated crops first or whether agriculture is inherently superior to foraging, it is more meaningful to think about how the domestication of plants influenced human society.

As humans shaped the evolution of crop plants, domesticated plants shaped the evolution of human society. As our food source became stationary and more reliable, human beings established permanent settlements. We as a society coevolved with the plants we selected for their desirable traits.

The significance of plants is not limited to their use as food. Plants have been used by human beings throughout history to construct a myriad of products from weaponry and shelter to baskets and ornaments. In addition to early domestication for food, some plant species were domesticated as sources of fiber. There is archeological evidence that flax (used to make linen) was domesticated in the Middle East along with food crops. Beyond the mundane, some plants had and still have important religious significance. The date palm was mentioned numerous times in the Bible and is still used today in Christian religious ceremonies. The lotus was sacred to the Ancient Egyptians, Buddhists and Hindus. Plants were used to treat ailments in an attempt to alleviate suffering. Lastly, plants were used as important flavoring agents. It is folly to think that spices were used primarily to mask the flavor of rotten food. Herbs and spices were first used most likely for the sheer pleasure of their flavor, rather than as a way to show off oneís wealth and in some cases, with the unintended benefit of preserving the food.

Imperialism and the Age of Exploration

The rise of Imperialism and the Age of Exploration was fueled by the quest for plant products. The trade monopoly on spices and sugar from the Far East by the Venetians and the Muslim world was a driving force behind the early explorations by the Portuguese.Prince Henry (Henry the Navigator) of Portugal established one of the first schools of navigation where the early explorers were trained and sent on a quest to bypass the monopolies on these valuable products.

Further explorations, including those that lead to the discovery of the New World, were also motivated by a quest for plants and the products they produced. The rise of slavery in the New World is directly tied to plants. Sugar plantations were established in the tropics of the New World for sugar production to crush the Venetian monopoly on the sugar trade from India and the Far East. With the plantations came the establishment of the slave trade. The importation of an enslaved labor force was the first mass migration of people to the Americas. The sugar plantations opened an ugly chapter in the history of Western civilization.

Photosynthesis

Plants play a fundamental role in supporting all life on earth. Plants are the basis of nearly all terrestrial food chains for humans and other heterotrophic organisms. Through the process of photosynthesis, they serve as the entry point of sun energy that is essential for maintaining ordered life on earth. They capture the power of the sun (radiant energy), convert it to chemical energy, and use that energy to fix carbon dioxide into useable sugars. During the conversion of sun energy to chemical energy, a handy byproduct (oxygen) is produced. Without this byproduct, there would be next to no oxygen in the atmosphere and no aerobic life on earth. You will learn more about photosynthesis later, but for now it is important to realize that the sugars and oxygen produced through photosynthesis make life on earth as we know it possible.

The Three Domain or Superkingdom System

Plants support a tremendous diversity of life on earth. Until recently, systematists subdivided this diversity into five major groups of organisms or Kingdoms. The area of organismal systematics is rapidly changing. The "Five Kingdom" system is giving way to a three domain or superkingdom system of the Archaea (ancient bacteria), the Eubacteria (true bacteria) and the Eukaryotes (organisms with nuclei). True plants as well as other eukaryotic photosynthetic organisms are found within this last domain.

For this course we will focus on Viridaeplantae (the green plants) as well as touch on members of other life lineages including the Fungi.? Within the green plant lineage, the majority of plants with which humans have contact are angiosperms (seed bearing, flowering plants). Seeds, fruits and other organs of angiosperms make up the bulk of the world's food.

Other seed bearing plants that do not produce fruits are commonly referred to as gymnosperms. "Gymno" is from the Greek word for "naked" (the original gymnasiums were populated by naked men exercising) so this term literally means "naked seed". The conifers, the largest group of gymnosperms, are also important as sources of wood, medicines, and even food. The most abundant and economically important plants, however, are the angiosperms. Not surprisingly, this is also the most diverse and arguably successful group of plants on earth.

The other major lineage of organisms with significance to this course is the fungi. This much maligned group of yeasts, mushrooms, molds and other filamentous decomposers and parasites were historically grouped with plants and thus will be touched on by this course. The fungi do not always deserve their low status. Without fungi, there would be no yeast-leavened bread, beer, or wine, nor would there be other important products like the antibiotic penicillin. Fungi have their darker side as well. They are responsible for diseases of both plants and humans, producing toxins that can kill and spoil food in storage.

The Six Major Categories of Plants that Serve Humanity

This course will explore six major categories of plants that serve humanity. After an introduction to the basics of plant science, food plants will be discussed. Plants provide an astounding and delectable variety of foods though it is somewhat disturbing when one considers the limited genetic basis that supports the bulk of the worldís growing population. Other than leather, fur, silk and most synthetic fibers, the fibers used in clothing are of plant origin.

The second category of plant usage, plants as materials, will be addressed. Plants are used to satisfy human needs beyond the basics of food and shelter.

What is food without flavor? And other than salt, most flavoring agents are derived from plants. Herbs, spices and flavoring agents will be discussed.?

The use of plants as medicines will be covered along with herbs and spices, as many flavoring agents from plants have been used in traditional medicines and the historical use of plants for medicines parallels their use for flavors. There is a fine line between medicine and poison.

Psychoactive and poisonous plants will follow the use of plants as medicines.

Beverages from plants and fungi will be discussed, including stimulating beverages such as coffee and tea and alcoholic drinks such as beer and wine that are products of fungal fermentation of plant materials.

Finally, the role of plants in the worldís ecosystems will be discussed in the last lesson. After reading the sections in your text, try to recall the numerous ways in which plants are beneficial in your life. Page through some of the other chapters to get an idea of the many other ways in which plants are useful.

Lesson 02: Plants in Life and in History (Printer Friendly Format)