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Chapter 1: Why plant science?

The study of plant science is one discipline of science that can help people understand the various changes in the environment in which they live. Plants are so essential in our daily life, and we need to understand them better.


After completing this chapter, you should be able to:

* Express an awareness of how plants survive in nature

* Relate the importance of plants in daily life

* Realize the esthetic and recreational significance of plants

* Describe the scientific method

* Discuss what the future holds for plant and man's relationship

Key Terms




carbon dioxide





scientific method

natural law

Every July, I watch eagerly a certain graveyard that I pass in
driving to and from my farm. It is time for a prairie birthday and
in one corner of this graveyard lives a surviving celebrant of that
once important event.

It is an ordinary graveyard, bordered by the usual spruces, and
studded with the usual pink granite or white marble headstones,
each with the usual Sunday bouquet of red or pink geraniums. It is
extraordinary only in beginning triangular instead of square, and
in harboring, within the sharp angle of its fence, a pinpoint
remnant of the native prairie on which the graveyard was
established in the 1840's. Heretofore unreachable by scythe or
mower, this yard-square relic of original Wisconsin gives birth,
each July, to a man-high stalk of compass plant or cut leaf Cutleaf
Silphium, spangled with saucer-sized yellow blooms resembling
sunflowers. It is the sole remnant of this plant along this
highway, perhaps the sole remnant in the western half of our
county. What a thousand acres of Silphium looked like when they
tickled the bellies of the buffalo is a question never again to be
answered, and perhaps not even asked.


This year I found Cutleaf Silphium in their first bloom on 24 July,
a week later than usual; during the last six years the average date
was 15 July. (See Figure 1-1.)

When I passed the graveyard again on 3rd of August the fence had
been removed by a road crew, and the Cutleaf Silphium cut. It is
easy now to predict the future; for a few years my Silphium will
try in vain to rise above the mowing machine, and then it will die.
With it will die the prairie epoch.

The Highway Department says that 100,000 cars pass yearly over this
route during the three summer months when the Silphium is in bloom.
In them must ride at least 100,000 people who have "taken" what is
called history, and perhaps 25,000 people who have "taken" what is
called Horticulture. Yet I doubt whether a dozen have seen the
Silphium, and of these hardly one will notice its demise. If I were
to tell a preacher of the adjoining church that the road crew has
been burning history books in his cemetery under the guise of
mowing weeds, he would be amazed and uncomprehending. How could a
weed be a book?

This is one little episode in the funeral of the native flora,
which in turn is one episode in the funeral of the flora of the
world. Mechanized man, oblivious of floras, is proud of his
progress in clearing up the landscape on which, willy-nilly; he
must live out his days. It might be wise to prohibit at once all
teaching of real horticulture and real history, lest some future
citizen suffer qualms about the floristic price of his good life
(Leopold, 1949).


Aldo Leopold, one of history's great conservationists, and a
cofounder of The Wilderness Society, wrote the preceding essay out
of concern not only for Silphium but for all plants and their
importance to our world. Likewise, this book is concerned with
helping you to develop an appreciation for plant science--the study
of plants--and the impact of plants on your life. Leopold's
statement that the teaching of plant science should perhaps be
prohibited was made tongue-in-cheek. He meant to convey that
studying plant science fosters an awareness of the crucial role of
plants to the functioning of the world.

We appreciate plants for their contributions both to natural beauty
and to our recreational pursuits in homes, gardens, parks, and
wilderness areas. They enhance our enjoyment of life. However,
other roles of plants come to mind; for example, plants are
important for shelter, clothing, and diet. Wood is the world's most
common building material, cotton is one of our basic fabrics, and
fruits and vegetables are part of a balanced diet. The utility of
plants in everyday life should not be underrated.

The most fundamental value of plants, however, lies in yet another
dimension. They are vital members of our ecosystem (see Figure
1-2). Plants produce the oxygen that we breathe approximately every
5 seconds. Also, by the process of photosynthesis, they convert
light energy to food energy. This benefits not only human
consumption and sustenance, but also other members of the animal
kingdom, who are in turn food sources for each other and for us.
Just how crucial is the role of photosynthesis in the function of
the world? No other organisms, including humans, would exist on
earth were it not for plants and other photosynthetic organisms.

A Sand County Almanac, with other essays on conservation for Round
River by Aldo Leopold. Oxford University Press.

Plants and Nature

The role of a single species, let alone a single plant, in the balanced functioning of any natural habitat can be overlooked easily. Leopold's awareness that this lone Silphium plant was a remnant of the native prairie and a relic of original Wisconsin demonstrates his understanding of natural communities. Before clearing and plowing for cultivation were undertaken, the prairie species provided food for the wild animals of the region. From the buffalo to the smallest field mouse, diverse and numerous plants and animals found there coexisted in balance. Even ranching activities placed an unnatural burden on part of the native flora, resulting in permanent changes in the number of species and their densities. There are precious few native prairies, or even small plots, still intact in North America. Their use to human society as valuable pasture or farmland has irretrievably altered their floristic composition. Unfortunately, the same circumstance is true in all the major prairies of the world. Forests and even deserts are now being irreversibly changed according to the short-term interests of human society. The importance of plants in the balanced functioning of the biological world cannot be overemphasized. Even though plants may have applied uses and cultural importance in the development and maintenance of the human population, they act most significantly in the natural balance of all biological energy and of atmospheric oxygen and carbon dioxide.

The source for all energy available to living organisms is the sun. The warmth provided by the sun's rays make the earth habitable, and in plant tissues sunlight energy is converted to food in the form of carbohydrates. Green plants, then, are the primary producers of food for the rest of the biological world, food that is subsequently converted to growth energy nutrients from the soil and carbon dioxide from the atmosphere in a process called photosynthesis. One of the end products of this process is plant tissue, which can be used as food by animals. Another end product of this energy conversion is the production of oxygen.

The two important atmospheric components for life on earth are oxygen and carbon dioxide. Animals must have a constant supply of oxygen to carry out the metabolic process that converts food tissues into a form of energy that allows muscle contraction, brain functioning, new growth, and ultimately the perpetuation of the species. Plants, too, need oxygen to carry on their life processes. The source for all atmospheric oxygen is the same plant process that converts light energy to carbohydrates--the process of photosynthesis is the most important chemical process known to humankind.

Since respiration, the utilization of food for producing a form of energy to do biological work, results in the release of carbon dioxide into the atmosphere, the balance of these essential gases is maintained. Plants carry out both processes, releasing both oxygen and carbon dioxide into the atmosphere, whereas animals are unable to produce oxygen. Water is an ingredient in both processes, cycling through plant, animals, the atmosphere, and soil.

Thus, if the natural functioning of plants is disrupted, the flow of energy, the exchange of oxygen and carbon dioxide, and the availability of fresh water are all affected. These balances are essential; disturbing them ultimately affects the very organisms that have brought about changes in the natural balances--humans.

In his forward to Sand County Almanac, Leopold summarized the cause for these changes, "We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect," which is a true appreciation of what our responsibilities are within the natural standing of the plant world.

Economic Importance of Plants

Although Leopold made no direct allusion to any potential economic value of Silphium, his description of "saucer-sized yellow blooms resembling sunflowers" brings to mind an economically valuable relative. Prior to the commercial development of the giant Russian sunflower for seed and oil, it too was only a common prairie weed (Helianthus annuus). This, of course, is true for all economically valuable plants; at one time the native plants that gave rise to today's crops were of no greater value than the Silphium.

The development of agricultural crops is the foundation on which civilization was built and one of the key factors in the continuation of successful human population. Modern agriculture produces an incredible amount of food annually, but with continued growth of the world population further increases are necessary, as shown in Figure 1-3. From approximately 700,000 plant species known to exist, over 95% of all food consumed by humans comes from less than 20 species, and over 80% of the food consumed is from only six plant species. How many potentially valuable plant species are yet to be discovered and developed, and how many are no longer available to fulfill such potential?


The natural world still contains a vast array of different kinds of organisms, yet each day sees the extinction of additional species. No one can adequately predict the consequence of that loss to the world. It is quite possible that some other mowing machine in some other graveyard has just destroyed a plant with the genetic potential for becoming a major world food crop. It is equally possible that there are many plants still plentiful that have undiscovered potential. These plants need to be found and studied.

Plants influence both conscious and unconscious decisions, even though most of us are unaware of their presence until we really need them, as at mealtime. The entire economic stability of many nations depends heavily on importing and exporting plant products. As the world's human population continues to grow, the economic importance of plants and plant products becomes even more significant.

Every time we pay for groceries we buy, the economic importance of plants for food is clear-sometimes painfully so. From the produce aisle with its array of fresh fruits and vegetables through the canned goods to the bakery items, essentially everything we buy is directly or indirectly produced from plants or plant extracts (see Figure 1-4). The meats and dairy products would be unavailable without adequate feed for the domesticated animals from which they come. Even the cash register tape, the boxes, or sacks in which our groceries are placed, and the cash used to pay for these purchases are plant products.



In winter, many tons of firewood provides heat throughout the world. Additional energy comes from organic materials that lived many millions of years ago, as shown in Figure 1-5. Essentially all of these organisms were plant materials at one time. Thus, products from plants are available to us in the form of synthetic fibers, plastics, and other materials manufactured from petroleum by-products.

The opium poppy shown is Figure 1-6 is one of the plants that provides two types of drugs, a widely used pain reliever and the hard core drug heroin. Synthetic pharmaceuticals are based on natural compounds first found in plants, bacteria, or fungi. The two most widely used pain relievers, morphine and aspirin (salicylic acid), are such compounds. Socrates was put to death with juice from the hemlock plant, and the Roman emperor Nero ruled after his father, Claudius, was assassinated with poison mushrooms and monkshood juice. Curare-tipped arrows and blowgun darts have aided many native tribes in the Amazon jungles in centuries of successful hunting. Cannabis, the genus that produces hemp fibers for rope and the hallucinogen marijuana, is a well-known member of the plant world.


Many plants have industrial applications as well. Their impact on the historical development of modern civilization is vast. Natural rubber is from a tropical tree, and from another tropical species comes the only source for carnauba wax, the hardest of the natural waxes for polishes and industrial application uses. Many of the finest lubricating oils for industrial machinery are found in plants, and various other plant extracts are important to a broad spectrum of industrial applications. Seeds from the jojoba, a desert shrub, yield a substitute for the sperm whale oil with which it shares almost identical chemical properties. Fibers for clothing, string, twine, and canvas come from plant sources, the most widely used being cotton. Dyes, essential oils for linoleum, plastics, soaps, and many other products are also derivatives of plants and plant parts. Thus for food, forage, fiber, fuels, medicine, and varied industrial uses, plants have by far the greatest economic impact of any group of living organisms.



Aesthetic and Recreational Significance

Leopold's aesthetic sense must have been acute indeed. In the introduction essay, his finely tuned appreciation for such a simple scene as the decorative yellow Silphium blossom against the backdrop of a country graveyard rings out. Leopold imagined that scene in another era, when millions of Silphium plants must have created the illusion of large, yellow inland seas. In our parks and botanical gardens, plants provide panoramic beauty. On a somewhat smaller scale, they provide shade and allow us to bring nature into our homes, businesses, and schools.

Sociobiologists contend that humans are genetically adapted to be comfortable in "natural" settings, but their immediate environment has evolved to include ever-increasing surroundings of metal, concrete, and plastic. Many people have learned to spend most of their time in such "unnatural" surroundings without any outward signs of physical or psychological discomfort. Others have not. In any case, a great many find enjoyment and relaxation when they are able to "return to nature" by camping, picnicking, sitting under a tree, walking barefoot in the grass, or backpacking as you can see in Figure 1-7. But many urban dwellers enjoy such opportunities infrequently, if at all. Thus, state and national parks and wilderness areas understandably are chosen more and more often as vacation spots (see Figure 1-8). As you can see in Figure 1-9, the natural beauty and integrity of such areas must be preserved if they are to continue to provide the relaxation and recreation people seek there, in other words, we are loving our parks and natural areas to death.

Among the multitude of recreational activities humans have devised, and one of the most consistently popular, is golf. The proximity of the trees, hills, water, and grass of a golf course gives the feeling of bringing in a natural setting without having to invest hours of travel to reach it. Walking and jogging through city parks are also popular forms of recreation that can bring the participant in closer contact with plants and nature. Even gardening and weekend yard work is a popular recreational activity that provides a much welcome involvement in the plant world.

We humans also attempt to bring nature into our plastic worlds by "greening ourselves in" with houseplants and landscaping our living spaces. The popularity of houseplants in working and living environments supports the theory that humans are genetically adapted to an environment in which we coexist with other living components of nature. There is even considerable evidence that mixing soil, pruning, watering, fertilizing, and tending to living plants is an excellent form of therapy, a subtle means of communing with nature by substituting houseplants for the larger and less accessible natural world (see Figure 1-10).



An understanding of how biological, geological, and environmental factors combine to produce the beauty of the natural world maximizes our appreciation and enjoyment of them, but it also helps us to understand how such beauty can best be maintained and preserved.

Plants in Science and Technology

The term science permeates every aspect of modern society. Food, consumer products, and even ideologies are scientifically designed, produced, and developed. There are natural, physical, political, and even social sciences. The scientific label has become a symbol of credibility, and yet a larger segment of the human population still perceives science as a secretive and/or a mystical activity. Scientists are often depicted as rather strange white-collared people with exceptional IQs who converse only in five-syllable words and mathematical formulas, often with beeping, blinking computers. Scientists are a diverse group of people observing, experimenting, and looking for new technologies and solutions to world problems.

Heredity and environment combine to shape the unique course of each of our lives. Similarly, our unique circumstances determines the type of associations we have with other parts of the biological world. Whatever our life's pattern, each of us will always have one or more relationships with the plant kingdom, be it as a consumer of shelter, clothing, and food, a guardian of houseplants and gardens, a wilderness lover, an agriculturist, or perhaps a biologist. In any event, an understanding of individual plants, and plant groups and their relationship to the rest of the biosphere, affords us a viewpoint that will enhance our associations with plants.

But how does one understand plants? How does one know about any aspect of the physical and biological world? Most of our understanding is based on previous observations and discoveries of others. This text, for example, contains information based on a systemic assemblage of information from prehistoric to present times, organized into facts and theories. A fact is an idea that is known and specific. A theory is an idea expanded from facts via reasoning but is not currently known to be entirely or universally true. The investigation process that incorporates reasoning and observation, with the objective of reaching theory or fact, is called the scientific method.

Leopold's careful observation of the flowering dates for Silphium would have been missed by most of us. Who cares if flowering occurred on July 24, a week later than usual? Why did he make such an observation? Leopold was practicing science, that is, he was increasing his understanding of an event by using the scientific method. To this purpose he probably kept a diary describing personal observations in nature.

The Scientific Method

The scientific method always starts with a certain base of facts--what is known. In observing the flowering dates of Silphium, Leopold may have been collecting an information base from which he then could have generated a theory about the general flowering time for Silphium. Or, perhaps already having a hypothesis or testable assumption about why the flowering time for Silphium was later than usual, he might have been seeking out a cause and effect relationship for flowering time. The goal of the scientist is to observe with accuracy so both reasoning and observation come into play. Science is the systematic accumulation of knowledge through the use of logic based on factual evidence. It is both an organized body of facts and a method of problem solving. The scientific method is the process of acquiring factual knowledge and for solving problems.

Briefly, the scientific method is a repeated sequence of events that includes the following steps:

* Recognition of a problem.

* Establishment of a hypothesis to explain or solve the problem.

* Careful observation to gather factual information relative to the problem.

* Reconsideration of the hypothesis in light of the accumulated facts.

* Testing of the hypothesis to establish repeatability and thus validity of the facts.

The scientific method is not to be regarded as inflexible or infallible. The important parts of an attempt to approach anything scientifically are accurate observations and objective interpretation. The number of observations made, the number of different observers involved, the analysis of the accumulated facts, the questions asked, and the sequence in which all of this transpires are not the same from one situation to the next. The basic goals, however, are the same; observation, hypothesis formation, testing, and repeatability to confirm validity all must be present for science to function properly.

When a theory or hypothesis has been repeatedly tested many thousands of times with the same results, it can be said to be a natural law. Few theories are considered laws, since there is a lack of sufficient experimental evidence to prove that there are no exceptions to the predicted results; one of the laws of nature is that of gravity. It can safely be predicated that, on the earth, every time an object is dropped it will move toward the center of the earth. To date there are no exceptions to this law; even through it has been tested in countless different ways.

Science does not attempt to determine what is "good" or "evil." Nor does it have a moral purpose, or does it attempt to convince anyone of anything. Science is simply an approach to establish what is and what is not factual. Science is not a world only for the scientist; everybody can and does practice science.

Approaching an everyday situation scientifically is a matter of being objective and following a logical sequence through to the end. Comparison shopping for the best value for your dollar is essentially a scientific process of deciding among many possibilities that are closest to satisfying one's needs. Science in this context is basically an attempt to remove rumor and hearsay from the process, replacing them with facts and objective evaluation of reliability, performance, and durability. Actually, purchasing an item is even a continuation of the process; using the item in question can be viewed as an experiment. The owner makes observations and comparisons of actual and claimed performance levels, which establish scientifically the validity of the manufacturer's claims.

So science is not mystical or limited to unique intellect or personality. Science is basic and understandable in design, although many of the facts and hypotheses are specific to each area of specialization. It is the framework in which knowledge is accumulated. Biology is the study of all living organisms; plant science is the study of plants. More and more specialized subdisciplines delve into greater understanding of organisms, furthering the accumulation of knowledge.

More on the Scientific Method

Nonscientists seem to believe that the scientist is a person with secret means of obtaining knowledge to benefit humankind. Explanations put forth by research scientists may be wrong as often as they are right. And not all discoveries directly benefit humans. Indeed, some seem completely useless or detrimental. Some individuals take another view of the scientific method. They infer that science is simply doing one's best with one's mind with no limits to creative approaches. This view indicates that the means used by scientists in solving problems are not unique to science. In fact, the scientific method can be used by anyone to solve a variety of problems.

There are thought processes that have to be used, when working with the scientific method. Experimental results are used, when necessary, to modify a hypothesis and to test predictions, but the cycle of testing really never ends. One could say it is a process of continuous improvement.

The scientific method begins with a hypothesis, and then moves
forward by testing the hypothesis. A hypothesis is simply a
tentative explanation-a guess--put forth to account for a set of
observations. Sometimes hypotheses have been called "educated

A hypothesis is a tentative statement or assumption that is made in
order to be tested. To formulate a hypothesis is to make a testable
prediction about the relationship between variables. A hypothesis
is usually stated before any sensible investigation or experiment
is performed because the hypothesis provides guidance to an
investigator about the data to collect. A hypothesis is an
expression of what the investigator thinks will be the effect of
the manipulated (independent) variable on the responding
(dependent) variable. Hypotheses can usually be formed as an "if
... then" statement.

The concept of hypothesis testing is basic to all science, and it
is also the most misunderstood by the public. The word prove should
not exist in the scientist's vocabulary, since an infinite number
of examples are needed to prove a hypothesis.

No matter how much evidence we gather to support a specific
hypothesis, we can never be certain that the same data would not
equally support any number of unknown alternative hypotheses.

After forming a hypothesis, a scientist proceeds by designing and
performing experiments. The primary purpose of scientific
experimentation is to test hypotheses. So, any hypothesis selected
by a scientist to explain a natural phenomenon must meet a very
important requirement: It must be testable.

Plant scientists rarely deal with cases in which every prediction
made by a hypothesis turns out to be correct. The question then
becomes: How many or what proportion of a given number of
predictions must be verified in order to make the hypothesis a
useful one? For this reason, experimental data are subjected to a
statistical analysis--mathematics used to determine whether
deviations from the pattern that is predicted by the hypothesis are

Plants and Society

The twenty-first century has suddenly thrust on both developed and underdeveloped countries complications not ever dreamed of by our forebears. Events that now affect our daily lives would have sounded like scientific fiction in the 1940s or 1950s. Technological advancement has developed at an incredible rate causing some sociologists to wonder if it would not have been better had certain advancements never been made. As developed countries take advantage of the luxury of goods and services, all at the expense of tremendous energy consumption, underdeveloped countries, seeing the splendor, suddenly rush to share it. The world's transportation and communication systems have decreased at a phenomenal rate; we can know "what's going on" virtually anywhere on the globe. What does all this have to do with plant science? The realization is that conventional food, fiber, forage, and energy resources are not inexhaustible. This has forced world leaders to consider where all the above-mentioned resources came from in the first place. Fortunately, the sun continues to supply sufficient radiation to keep the earth warm, but that is not enough to guarantee future human success. As long as the sun does provide sufficient heat and light, the role of plants to the very existence of humans on this planet remains critical. The interdependence of plant and animal life, especially human life, is and always will be of primary ecological importance. It is now crucial for average citizens to understand botanical implications so they can make intelligent decisions concerning the future. These are no easy decisions, either for the politician or the voter. Some of today's social problems are overpopulation, inadequate food supply, and a reduced quality of life as you can see in Figure 1-11.


Does one nation with food have the right to dictate philosophy to another nation and use that food as a political weapon? Is it worth the environmental risk necessary to develop a supply of nuclear energy? Does one state have the right to take water from another state (nation) that has an abundant supply but might need it in the future? Are you willing to pay a great deal more for environmental monitoring to ensure that the water you drink, the food you eat, and the air you breathe are safe?

In a botanical sense, there exists a serious set of questions: How can we grow enough food to feed a world population two, three, or four times as large as our current one? What do we do if the quality of both drinking water and irrigation water becomes so poor that the animals and plants being grown no longer produce effectively? What do we do if the air becomes so poor that plants will no longer grow?

These are not hypothetical questions but rather real, current concerns faced by today's leaders. In a democracy, only a qualified electorate can make those decisions. As part of that electorate, voters need to understand that knowledge plays a serious part in the botanical world and everything that depends on it.


1. Plants are critical to continued human existence for aesthetic, economic, and ecological reasons.

2. Plants are the producer organisms for the world, converting sunshine into chemical energy for all organisms while releasing oxygen into the atmosphere. Ecosystems function properly only as long as nature is in balance.

3. Plants are the producers for all living organisms. Those, which grew millions of years ago, provide the world with fossil fuels, and modern plants provide humans and animals with food, shelter, medicine, fibers for clothing, and thousands of industrial products.

4. Plants permeate our conscious and subconscious lives in the form of nature, from which we have never totally separated ourselves. Parks, wilderness areas, and both interior and exterior landscaping remain at the center of human attempts to bring tranquility and beauty into a hurried, competitive, synthetic world.

5. Scientific inquiry begins with recognition of a problem, followed by establishment of a hypothesis, observation, reevaluation of the hypothesis, and finally testing of the hypothesis for repeatability and validity.

6. National and worldwide food, energy, and water shortages are problems that must be faced by both governmental leaders and citizens. As informed voters, those of us living in a democracy have the opportunity to help protect our botanical world.

Something to Think About

1. How can we grow enough food to feed a world population two, three, or four times as large as it is today?

2. What do we do if the quality of both drinking water and irrigation water becomes to poor that the animals and plants being grown no longer produce effectively?

3. What do we do if the air becomes so polluted that plants will no longer grow?

4. List how plants are used in everyday life.

5. Why are our national parks being loved to death?

6. Explain the scientific method and how it is used.

Suggested Readings

Biello, D. 2007. Many plants can adapt when climate goes against the grain. Scientific American.

Holland, A., and K. Rawles. 1993. Values in Conservation, ECOS, 14(1).

Leopold, A. 1949. A sand county almanac. New York: Oxford University Press.

Leu, A. 2004. Organic agriculture can feed the world. Acres USA. Plants in daily life. 2005. London: Royal Horticulture Society.


Internet sites represent a vast resource of information. The URLs for Web sites can change. Using one of the search engines on the Internet, such as Google, Yahoo!, or MSN Live Search, find more information by searching for these words or phrases: scientific method, hypothesis, testing, repeatability, and aesthetic and recreational significance of plants: Aldo Leopold, aesthetic significance of plants, recreational significance of plants, scientific method, hypothesis formation, testing, validity, and urban living.
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Title Annotation:PART 1: Plants and Nature
Publication:Fundamentals of Plant Science
Date:Jan 1, 2009
Next Article:Chapter 2: Plants and ecology.

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