Read an Excerpt
CHAPTER 1
What Is a Plant?
When you peer into a full-length mirror you see a reflection of yourself: a human figure made up of all your body parts. Each of these parts has more parts: your head is made up of ears, eyes, a nose, a mouth, a chin, a forehead, and cheeks. Humans and many other animals have parts in twos or multiples of two.
Now compare yourself with the "body" of a plant. It obviously does not look like a person. So how do we describe a plant form?
Let's use a buttercup as an example. The buttercup plant is anchored by roots, out of which grows a stem. From the stem grow other stems, each bearing leaves, buds, and flowers. Each of these parts has more parts, just as a human arm has a hand with fingers and fingernails.
TRY THIS!
PLANT JOURNAL
Scrutinize, scribble, sketch! A plant journal can be like a travelogue describing the plants you meet. Make a journal and use it to record observations and sketches on your own or as you work through the activities in this book.
MATERIALS
* Notebook with unlined pages
* Colored markers, or scissors and old seed catalogs or gardening magazines (to decorate cover)
* Glue
* Your sharp eyes
* Magnifying glass
* Pen or pencil
* Colored pencils
1. Decorate the cover of your journal with drawings or with pictures cut out from seed catalogs or garden magazines.
2. Take an expedition around your neighborhood, school, or anywhere else you are likely to see plants.
3. Choose a plant to observe closely. Use your magnifying glass to get a close-up view.
4. Write down words that describe the unique characteristics of the plant.
5. Make sketches of different parts, such as leaves, stems, or flowers.
6. Record the location of the plant and any questions you have.
TRY THIS!
PLANT PORTRAIT
Observe, compose, sketch! Create a portrait of a houseplant or an outdoor plant in your yard or neighborhood.
MATERIALS
* Your sharp eyes
* Magnifying glass
* Plant journal
* Pencil
* Crayons, colored pencils, or markers
1. Choose an indoor or outdoor plant to observe.
2. Examine the plant carefully with the magnifying glass. Take notice of the shape of the stem, leaves, and other parts.
3. In your plant journal, do a quick sketch of the whole plant in pencil before adding details in color.
Plant or Not?
Do all plants have leaves, roots, stems, flowers, and seeds? No. Unlike birds, which all have feathers, not all plants possess the same features. For example, Indian pipe lacks leaves. Watermeal, a common pond plant, is missing stems and roots. Mosses have leaves and stems but no flowers, seeds, or real roots. They have rootlike structures that anchor them but don't transport water.
The plant kingdom contains a wide range of organisms, including green algae, mosses, ferns, herbs, vines, shrubs, and trees (which are not covered in this book). The majority of plants use sunlight to produce their own food from nutrients and water, though there are exceptions like Indian pipe, which doesn't need leaves because it gets sugars from soil fungi.
Plant Speak
People who study plants are called botanists. Like artists, electricians, and nurses, they use a special vocabulary. Botanical language allows botanists to describe plants in a concise way. The only problem is if you don't know the language, you have no idea what a botanist means when he or she says that a plant is an autotroph (makes its own food) or is biennial (lives its whole life in two years).
Learning a new language can be a challenge, but just imagine being able to speak like a botanist with words like pistil, glochid, and gymnosperm rolling off your tongue. The next paragraph includes a few new words to start with.
Plants belong to the kingdom Plantae. Each unique type of plant is classed as a species. The common dandelion species, for example, is Taraxacum officinale. This name is composed of two parts: Taraxacum is the genus name, and officinale is the species name. There are 60 other species of Taraxacum growing around the world. One species in California is very rare, one in Japan has white flowers, and another in Kazakhstan produces a natural rubber.
The First Plants: Algae
The first plants to appear on Earth were algae, which show up in fossils that date back 500 million years. Some algae were simply a single cell that used sunlight to transform a gas called carbon dioxide and water into sugars through a process called photosynthesis. Others were minute threadlike strands, or filaments, that floated in water. They were very basic plants that lacked leaves, roots, flowers, and seeds.
Among algae living on Earth today are micro (small) and macro (large) species. In freshwater ponds, a green micro alga called spirogyra can be found growing in large, slimy masses. Chlorella is another single-cell alga known for its rapid reproduction.
Along the seashore, you may find a common green macro alga, such as sea lettuce or gutweed, growing in shallow water or washed up on the shore. Dwarf rockweed, another macro alga, can be found clinging to rocks submerged during high tide. These marine algae, or seaweeds, take in water and nutrients from seawater through all of their tissues. Unlike most land plants, they don't have roots or interior veins to transport water or nutrients.
Solar Food Factories: Photosynthesis
Every day as sunlight shines upon leaves, something amazing occurs. We can't see, feel, or hear it, but we can see the results as we watch plants grow. Using the energy from sunlight, plants transform water and carbon dioxide into sugar and oxygen in a process called photosynthesis.
This action depends on a substance called chlorophyll, which breaks apart molecules of water and carbon dioxide and re-forms them as sugar and oxygen. Chlorophyll is found in plant structures called chloroplasts, which are like food factories where sugars are constantly being produced. These sugars are food for both the plant and any animals that eat the plant.
LOOK FOR
ALGAE EXPEDITION
Seek, search, but don't touch! You can look for algae in saltwater or fresh water. For safety reasons, invite an adult to join you while visiting any bodies of water to conduct your search. Freshwater algae may grow in large masses in ponds, canals, and lakes, especially where these bodies of water have been polluted. Runoff from farms and factories may contain fertilizers, manure, or other waste that certain types of alga thrive in. These thick masses of alga that turn bodies of water into green soups or slimy mats are called algal blooms. Warning: Do not touch these algae! Just observe.
If you live near or can visit the seashore, go during low tide to view the greatest variety of algae.
Plants and animals need to take in oxygen to release the energy from the sugars. This process, called respiration, creates carbon dioxide that is released into the air. Plants respire at night, while animals respire both day and night.
In extreme hot or cold temperatures, plants photosynthesize more slowly or not at all. Plants growing in the chilly far north have leaves especially adapted for absorbing heat and light from the sun. These plants often grow low to the ground to benefit from the warmth of sun-heated soils and to avoid cold winds.
CELLS AND MORE CELLS
Cells are the building blocks of all organisms. They are composed of a cell membrane, a kind of skin, that holds a material called cytoplasm, which contains proteins and nucleic acids. The largest plant cell is a single-cell alga called Acetabularia. It looks like an underwater mushroom and can grow as high as a tennis ball.
Scientists believe the first life forms to appear on Earth, about three billion years ago, were single-cell organisms called Archaea. These microscopic cells were the only organisms for a long time before multicellular life evolved.
Depending on their size, most plants contain billions of cells. A human is made up of more than 10 trillion cells!
Plants in dry, hot deserts survive because they have leaves that conserve water. Desert plants also have hairs that shade the leaf surface and reflect sunlight, which helps them stay cool.
The hundreds of thousands of plant species have an incredible variety of leaf shapes and sizes. Different types of leaves enable each plant to photosynthesize for each special growing condition.
Humble Mosses
Growing in sidewalk cracks, on shaded tree trunks, and on roof shingles, mosses usually don't earn the oohs and aahs reserved for flashy flowers and colorful vines. But they do deserve respect for being the first plants to colonize the Earth's land surface more than 450 million years ago.
Without true roots to suck up water or stems to stand tall, mosses still thrive. Using water from moist soil, rain, and fog, they grow where bigger, showier plants can't survive. Red roof moss is one of the first plants to appear after a fire. Antarctic moss withstands frigid weather by growing on penguin poop. Though small and seemingly fragile, Antarctic moss buried in frozen ground for more than 1,000 years can be revived to grow again. Sphagnum, also called peat moss, can increase in weight more than 25 times when it gets wet. It's no wonder that it was used as the original disposable diaper. Not only did it soak up baby pee, but the moss's natural acidity also prevented diaper rash.
Scientists believe that mosses may have even changed the Earth's climate from hot to cold by removing carbon dioxide from the Earth's atmosphere. Carbon dioxide acts as a blanket that holds in the Earth's heat. As mosses grow they release acids that dissolve the surface of rocks. During this process, carbon dioxide gas is removed from the air and combined with water to become carbonic acid. In this form, carbon is carried to the sea by streams and rivers, where it is locked away in carbonate rocks, such as limestone. Millions of years ago, when mosses were the dominant land plant, a massive amount of carbon was removed from the air in this way and transformed into rock.
TRY THIS!
VISIT THE MOSS WORLD
Peer, poke, pet! When moss is moist, it is a soft and intricate green landscape teeming with tiny creatures.
MATERIALS
* Your sharp eyes
* Magnifying glass
* Pen or pencil
* Plant journal
1. Look for moss outside. You might find moss in shady locations at the base of a tree or on its trunk, in a sidewalk crack, or on a forest floor. Notice the shape of the moss's stems and leaves. Using a magnifying glass, you might see a tiny forest of fernlike plants. You might also see a landscape of strange forms, from tonguelike leaves to tiny spears, and even structures that look like tiny palm trees and vases. Liverworts, hornworts, and mosses are known as bryophytes, from the Greek meaning "tree-moss plant."
2. Look for creatures living in the moss, such as mites or springtails. Mites eat both plant material and other small creatures. Springtails devour spores, pollen, bacteria, and strands of fungi. Both are arthropods — animals with jointed legs. Like insects, springtails have six legs, while mites have eight legs like their close relatives, spiders.
3. Record your observations in your plant journal.
As more and more carbon was captured in the sea and stored in rock, the blanket of carbon dioxide covering Earth became thinner and held in less of the Earth's heat. The planet cooled, and an ice age began.
For the next 100 million years mosses and their relatives, liverworts and hornworts, were the main plants growing on land. Because they have no roots, they grew only in wet or moist areas.
Moss Cousins
The name of the moss relative liverwort comes from the liver-like shape of the plant's thallus (leaflike structure). Over 100 years ago, people believed a plant or plant part shaped like an organ in the human body could be used as a medicine to cure ailments of that organ. Wort is a very old word for a plant with a medicinal use. Liverwort is still used in China to treat liver disorders such as jaundice and hepatitis.
Another moss cousin, hornwort, is named for the hornlike shape of its reproductive structure. Unlike mosses, hornworts and liverworts have flattened leaflike structures. Mosses' reproductive structures look like caps on stalks. Liverworts' structures look like small umbrellas, and hornworts' structures resemble animal horns.
Plants with Plumbing
Picture a forest, not of pine and oak trees but of giant plants with trunks bearing rings of feathery branches. You might spy giant amphibians or insects roaming the swampy forest floor. Huge dragonflies with wingspans of three feet (75 centimeters) dart through the air. This world has been revealed by fossils of plants and animals discovered in 350-million-year-old coal deposits. These ancient plants existed long before the days of dinosaurs. Unlike mosses, these plants, called lycopods, had leaves, each with a single vein. With this simple plumbing system, water could flow up into the plants' stems and leaves. These plants could grow taller than the ground-hugging mosses, liverworts, and hornworts. In fact, one species, Lepidodendron (meaning "scale tree"), grew up to 100 feet (30 meters) tall.
Just like the modern descendants of ancient dragonflies with three-foot (1-meter) wingspans, the modern relatives of these early forest plants have also shrunk in size. Modern lycopods, such as spike moss, club moss, and quillworts, are all low-growing plants. Both spike mosses and club mosses have scalelike leaves, short branching stems, and simple roots. One species of spike moss is called resurrection moss. In arid areas, during long periods without rain, it curls inward as it dries up. Later, when it receives water, the leaves suddenly unfold and turn green.
Many of the club mosses, such as ground pine that grows on the forest floor, look like miniature trees. Named for their hollow, quill-like leaves that can grow up to three feet (about 1 meter) long, quillworts grow in wet or moist places. Some species live underwater.
Feathery Ferns and Hairy Horsetails
Three hundred million years ago, ferns became so dominant that this period is known as the Age of Ferns. The feather-like leaves of ferns, called fronds, are found in coal deposits along with a closely related plant called horsetail. Once treelike, most species of ferns and horsetails are now low-growing. Horsetails are also called scouring brushes because their tough leaves are useful for cleaning pots.
Ferns grow throughout the world, from the small brittle fern growing on islands in the Arctic to the bog fern found only on Tristan da Cunha, a remote island in the South Atlantic Ocean. Ferns and horsetails have a more complex vein, or vascular, structure than the plants that came before them.
Unlike a rose bush or bean plant, ferns grow from rootlike stems called rhizomes that lie on the ground. From these stems grow upright, stemlike structures called stipes. The upper part of the stipe, where leaflike pinnae (leaflets) grow, is called the rachis (meaning "spine"). The stipe, rachis, and pinna are all parts of the fern frond.
The underside of pinnae may have small round or oval structures. Called sori, these are clusters of sporangia, which produce spores. New ferns grow from spores.
Advanced Plumbing
Plants that have roots and well-developed plumbing to transport water and sugars are called vascular plants. They grow in a variety of forms.
* Forbs: A dandelion weed, a broccoli plant, and a sunflower all have nonwoody stems and are called forbs or herbaceous plants. Forbs can be as tiny as duckweed or as large as a banana plant, which grows to the size of a small tree but lacks a woody trunk.
* Shrubs: A plant with many woody stems, like a rose or blueberry plant, is called a shrub or bush. Some shrubs, like alpine laurels, may grow only a few inches high, while others like redbud may grow 20 feet (6 meters) tall. Shrubs usually have well-developed root systems and stems.
* Vines: Plants like honeysuckle or poison ivy that sprawl along the ground like a snake or climb up tree trunks or other surfaces are called vines. Vines have flexible stems that may become rigid as they age. Some are herbaceous, such as morning glory, and others are woody, such as wisteria.
(Continues…)
Excerpted from "Plantology"
by .
Copyright © 2019 Michael Elsohn Ross.
Excerpted by permission of Chicago Review Press Incorporated.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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