Over the years, I have had the pleasure of introducing countless numbers of people to plant science. My desire to relate the wonders of plant biology, and its relationship to our daily lives, inspired me to write this article.
The science of botany is divided into various disciplines, each having its specialties. Among them, cytology (Greek: kytos, meaning “container”) is the detailed study of cells. Study of the form and structure of plants is the work of morphologists (Greek: morphe, meaning “form”). Most gardeners are more familiar with morphology than with cytology. Basic understanding of how plants function makes gardening more enjoyable. It also makes us better gardeners.
Let’s examine the fascinating world of plant biology: plant cell formation, plant form and structure, and how plants function.
Plant benefits to humans and other life
Earth is covered with a green blanket of vegetation, and because of the diversity of Earth’s plants, other forms of life are sustainable. From the very beginning, plants evolved first among our planet’s living things. Plants, in one form or another, can exist without animals, but animals cannot exist without plants.
Since the birth of cells, millions of years ago, plants have been inextricably linked in an unbroken chain of life. Plants created the biosphere, the part of earth where both plants and animals exist. Humans and animals have depended on plants for survival from the very beginning of their existence. We have evolved from primitive beings to a modern, sophisticated civilization, through knowledge from one generation to another. Plants even made it possible for mankind to express, preserve, and pass along ideas, music, mathematical equations, and scientific findings, and more, because they could be written down on paper, which is made from plant material. Plants provide material for clothing, homes, furniture, and more, and medicines come from plants. In these ways and more, plants have improved mankind’s quality of life and longevity.
Plants clean the air; they exchange the oxygen that we inhale with the carbon dioxide we exhale. They photosynthesize energy into foods that sustain all animals, and from the soil, draw micronutrients, minerals, nitrogen, phosphors, potassium, calcium, and iron that are crucial for our existence and health.
Form and Structure
There are approximately 400,000 different kinds of plants called species, present in diverse forms. One-third of all plants do not have roots, stems, or leaves as we know them. About 150,000 plant species never produce flowers, and almost an equal number do not grow from seeds, but rather from dust-like particles called spores. Although the vast majority of plants manufacture their own foods by a process called photosynthesis, mushrooms, molds and other fungi—which some biologists include in the plant kingdom—rely on foods created by green plants, for their sustenance, as do animals. Most plants spend a lifetime anchored in one place; yet simple single-celled organisms called plankton are capable of swimming to different locations in the waters they inhabit.
Angiosperms and Gymnosperms
As we further discuss the science of botany, let’s focus on the two groups of plants that we as gardeners are most familiar with. First, the flowering plants, or angiosperms, is the largest group in the plant kingdom and consists of about 250,000 species. The name ”angiosperm” (Greek: angeion, meaning “vessel” and sperma, meaning “seed”) comes from the fact that seeds from these plants are formed inside containers (or vessels) that we know as “fruits.” These flowering plants are the ones that most often decorate our homes and landscapes, supply almost all of the vegetable matter in our diet, and are the source of the world’s hardwoods. They are the most sophisticated of plant forms and are best adapted to survive in a wide range of climates and places.
Second are gymnosperms, plants that produce seeds in the open spaces of cones. (For example: between the flap-like parts that make up a pine cone.) The Greek words gymnos, ”naked” and sperma, meaning ”seed” describe this form of development. Now you know where the term ”gymnasium” comes from. The ancient Greek gods used to develop their Adonis-like bodies in the nude, hence the prefix ”gym.” Gymnosperms include all the conifers, like cedar, redwood, juniper, cypress, fir and pine, and the largest living things on earth: the giant sequoias. Many ornamental shrubs—such as varieties of Chamaecyparis (False Cypress) and Thuja occidentalis (American Arborvitae)—are members of this group. So are less typical examples of gymnosperms, the Cycads, the beautiful maidenhair tree, and Ginkgo biloba, a broadleaved species.
How can we be so sure that the potted rose bush is living, but a petal of the same rose from the same plant, that was pressed and dried last year, is unquestionably dead? From all appearances, a seed also seems dead.
But when the pedal was a part of a living plant, its cells were actively engaged in a complicated chain of chemical reactions, grouped together under the term ”metabolism.” We can be quite sure that, as long as a cell or a whole creature is alive, it is going to display some sort of metabolic activity. When their chemistry irreversibly stops, cells die.
How plants function
Limits of plant growth are proportional to the availability of light, water, minerals, and oxygen. Lifespan is genetically determined, generally one year for annuals, two for biennials, and an indefinite period for perennials. You will also notice the term ”indeterminate” used on tomato plants. This refers to their growths habits. They will continue to grow until environmental conditions, such as cold weather, become a limiting factor.
With plenty of Dr. Earth® fertilizer, careful watering schedules, optimum sun energy, and proper thinning (the removal of plants that may compete for available nutrients and light) a plant can be pushed to the limits of leaf and flower production.
A plant is anchored in one place throughout its life. Half of its body—its root system—is buried in the dark, damp, and somewhat stuffy recesses of the soil. This is where half of the magic happens.
In contrast, shoot systems, consisting of stems and leaves, occupy a sunlit and airy world; this is where the other half of the growth magic occurs. Roots and shoots are frequently thought of as different entities, growing in opposite directions. To a plant, they are parts of the whole body that must be as well coordinated as are torso and legs during the course of human growth and the varied activities humans undertake. Root growth and shoot growth are harmonized events, one complementing the other, with energy reserves and raw materials shared equally by to the two halves. And when daily or seasonal environmental changes affect one part, the other must respond in sympathy. Fulfillment of the fundamental qualities of living things, such as reproduction, cellular metabolism, and growth, can only be achieved by such precisely controlled interactions between roots, stems, leaves and flowers.