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Caironi, Hernán Cañellas, Leonardo César, José Luis Corsetti, Vanina Farías, Joana Garrido, Celina Hilbert, Isidro López, Diego Martín, Jorge Martínez, Marco Menco, Ala de Mosca, Diego Mourelos, Eduardo Pérez, Javier Pérez, Ariel Piroyansky, Ariel Roldán, Marcel Socías, Néstor Taylor, Trebol Animation, Juan Venegas, Coralia Vignau, 3DN, 3DOM studio, Jorge Ivanovich, Fernando Ramallo, Constanza Vicco, Diego Mourelos Composition and Pre-press Services: Editorial Sol 90 Translation Services and Index: Publication Services, Inc. Portions © 2008 Encyclopædia Britannica, Inc. Encyclopædia Britannica, Britannica, and the thistle logo are registered trademarks of Encyclopædia Britannica, Inc. Britannica Illustrated Science Library Staff Encyclopædia Britannica, Inc. Editorial Jacob E. Safra, Chairman of the Board Michael Levy, Executive Editor, Core Editorial John Rafferty, Associate Editor, Earth Sciences Jorge Aguilar-Cauz, President William L. Hosch, Associate Editor, Mathematics and Computers Michael Ross, Senior Vice President, Corporate Development Kara Rogers, Associate Editor, Life Sciences Rob Curley, Senior Editor, Science and Technology Dale H. Hoiberg, Senior Vice President and Editor David Hayes, Special Projects Editor Marsha Mackenzie, Director of Production Art and Composition Steven N. Kapusta, Director Carol A. Gaines, Composition Supervisor Christine McCabe, Senior Illustrator International Standard Book Number (set): 978-1-59339-797-5 Media Acquisition International Standard Book Number (volume): Kathy Nakamura, Manager 978-1-59339-803-3 Britannica Illustrated Science Library: Copy Department Plants, Algae, and Fungi 2008 Sylvia Wallace, Director Julian Ronning, Supervisor Printed in China Information Management and Retrieval Sheila Vasich, Information Architect Production Control Marilyn L. Barton Manufacturing Kim Gerber, Director www.britannica.com Plants, Algae, and Fungi Contents Grain of mallow pollen, magnified 600 times, pictured on page 1. Pollen's function is to fertilize the female organs of the plant, a task that is achieved with the help of bees. Background Page 6 From Algae to Ferns Page 18 Seed Plants Page 34 Rare and Useful Plants Page 58 Fungi Page 80 Green magical. It is marvelous to understand how You may be surprised to learn why plants an organism that cannot move learned to invest so much energy and effort into Revolution maximize the energy that it receives from producing flowers. In this book we will the Sun, as well as to discover the describe for you in detail, step by step, how mechanisms that enable it to face so many fertilization takes place. Did you know that different environmental challenges. Some pollination is aided by the wind and insects leaves have essential adaptations, such as and that some flowers can be pollinated only thick skin, thorns, or fleshy stalks, which by a certain species of insect? You will find RICE CROP T here are approximately allow them to survive in very dry all this and much more in the pages of this Rice is synonymous with 300,000 plant species in environments. Others, such as the tomato book, which includes spectacular images and food security in much of Asia. It is also a staple the world, and they live in a plant, form certain proteins when illustrations that give an inside view of the food in western Africa, variety of regions, from the frozen temperatures drop in order to protect core of a tree and even show the functions of the Caribbean, and the tropical regions of Latin Arctic tundra to the lush tropical themselves from damage caused by freezing. its tissues and the veins of its leaves. America. rainforests. Without plants we would not be able to live; they have always W hat were the first plants to been intimately linked to life on conquer the Earth like, and how Earth. Thanks to photosynthesis, did they help convert bare rock plants provide us with food, into soil? What happened next, and which medicines, wood, resins, and species evolved and spread worldwide during oxygen, among other things. the Carboniferous Period? A complete Discovering plants' processes historical overview of plants is included in for converting sunlight into this book, as is an explanation of the radical carbohydrates such as sugars differences between plants, algae, and and starches is almost fungi—the latter two of which are now considered to be more closely related to animals than to plants. Although the place of plants in the human diet is nothing new, the search for other beneficial uses of plants is a more modern development. Crops— such as rice, corn, wheat, rye, barley, oats, soy, lentils, and chickpeas—are grown worldwide as sources of proteins, vitamins, minerals, and other nutrients necessary for our bodies to function, and they also provide people with an important source of income. Background GIANT SEQUOIA KINGDOMS OF THE QUIET LIFE 8-9 Some trees of this species are AQUATIC PLANTS 10-11 found in central California. CONQUEST OF LAND 12-13 ANATOMY OF A TREE 14-15 FEEDING ON LIGHT 16-17 A ccording to scientific which were at times dry and at times amazing growth, as exemplified by the that plants grow bigger as their cells evidence, the nearest relatives damp, the first land plants emerged. giant sequoia (Sequoiadendron multiply and expand? Many can grow 0.4 of plants are algae that lived Most had to adapt in order to prosper giganteum), which can measure 260 feet inch (1 cm) per day, and their growth can on the shores of lagoons. in a different environment. Such (80 m) tall and 100 feet (30 m) in create enough pressure to open cracks in Later, from these habitats, adaptation enabled them to achieve circumference at its base. Did you know asphalt. 8 BACKGROUND Kingdoms of the Quiet Life CONIFERS are the most abundant plants with seeds today. Their R epresenting a vast array of life-forms, the plant kingdom includes approxi- reproductive structures are called cones. Most conifers are mately 300,000 species. Their most outstanding feature is the presen- evergreens. ce of chloroplasts with chlorophyll, a pigment that enables them to transform solar energy into chemical energy. They use this energy to pro- Gymnosperma duce their food. Plants need to attach themselves to a substrate (usually The Greek word means “naked seed.” the ground), from which they can extract water and nutrients. This Gymnosperms are vascular plants with exposed seeds and no flowers. Ginkgos attachment, however, also keeps them from moving from place to place. (Ginkgophyta) and cycads (Cycadophyta) were Algae and fungi were once included in the plant kingdom, but they are the most common plant groups in ancient SITKA SPRUCE CYCADS GINKGOS GNETOPHYTA times. Today conifers (such as pines, larches, Picea sitchensis now considered to be separate from plants and to belong to the kingdoms are tropical plants that look Only one species Plants with naked cypresses, and firs) are the most common Protista and Fungi, respectively. like palm trees. Their is left in this seeds and a type. Conifers are monoicous—that is, the reproduction is similar to group, which is vascular system same plant has both male and female sexual MOSS that of pine trees, but they the oldest genus similar to that of organs—and their seeds are held between the Sphagnum sp. are dioecious (each plant has of living trees. angiosperms scales of a structure called a cone. flowers of only one sex). Algae Bryophytes Fungi are commonly considered water plants, but this is not the include mosses and worts. Mosses have rhizoids belong to a different kingdom from that of case. Algae have neither roots nor stalks. Because they live in rather than roots. They can also absorb water plants. Fungi, unlike plants, do not carry out the water (freshwater or salt water), they need no substrate. through their entire body surface. Bryophytes lack a photosynthesis, and they store energy in the Some are microscopic, but large algae formations can be means of surviving long periods of drought. When form of glycogen rather than starch. Fungi are found in the ocean. Algae are classified into families dry periods come, bryophytes enter a latent state. heterotrophic (they get their food from other depending on their color. Together green algae and plants Because they have no system of veins for organisms), and they take in food by absorption. make up the group of organisms called the “green line,” whose transporting nutrients, they can barely grow beyond Fungi can be either parasitic or feed on dead RED MARINE members are characterized by having chloroplasts and by 0.4 inch (1 cm) long. In order to reproduce they need organic material. Some fungi are microscopic; ALGA storing grains of starch in the cytoplasm as a reserve. to be near liquid water. Rhodomela sp. others are large and conspicuous. Their bodies are composed of a mycelium, a mass of filaments called hyphae. Some fungi also Plants have a fruit-bearing structure. WHITE MUSHROOM Cycads Agaricus bisporus The plant kingdom (Plantae) includes organisms Horsetail whose characteristics include the presence of the Rushes Psilophyta pigment chlorophyll to convert solar energy into Bryophytes Ginkgo chemical energy for producing food from water and (Mosses) Anthophyta carbon dioxide. This ability is called autotrophy. All or plants, whether large or small, play an extremely Flowering Green WHEAT important role in providing food for all other living Algae Club Gnetophyta Conifers Plants Triticum sp. beings. Plants cannot move from place to place, but Mosses Ferns their gametes, spores (cells that separate from a plant and can germinate), and seeds can move about, SEEDLESS WITH SEEDS especially with the help of water and wind. WITHOUT VEINS WITH VEINS PLANTS FERN Osmunda sp. Seedless Ferns are the most common seedless plants today. Many are thought to Angiosperms have originated during the Devonian Period and reached their greatest have seeds, flowers, and fruit. They include more splendor in the Carboniferous Period. than 250,000 species and are adapted to nearly all Their tissues are simpler than those environments except for Antarctica. They reproduce of plants with seeds, and their green sexually by producing flowers that later form fruits stems have a large surface area, with seeds. Angiosperms have an efficient vascular CEREALS FERNS SPIKE MOSS PSILOPHYTA HORSETAIL giving them a great capacity for ORCHIDS ORCHID system for transporting water (through the xylem) are monocotyledons. are the most diverse has scalelike are extremely simple RUSHES photosynthesis. Ferns need water so have many petals; their number Cattleya trianae and food (through the phloem). Angiosperms make Their seeds have only group of seedless leaves, some of plants; they lack have roots, stems, and that they can reproduce by means of of petals is always a multiple of up a division of the plant kingdom that includes one cotyledon plants. Their origin which are roots and true true leaves. The leaves spores. The spores are produced in three. This makes them, along plants with bright flowers; grains, such as rice and (embryonic leaf), and dates back to the clustered in the leaves, but they have are small and encircle spore cases called sporangia, which with cereal grains, wheat; other crops, such as cotton, tobacco, and their mature leaves Devonian Period. form of a spike. a stalk with veins. the stems. grow on leaves called sporophylls. monocotyledons (monocots). coffee; and trees, such as oak, cherry, and chestnut. have parallel veins. 10 BACKGROUND PPLANTS, ALGAE, AND FUNGI 11 Aquatic Plants 300 THE NUMBER OF WELL-KNOWN SPECIES Amphibious or Wetland Plants OF WATER PLANTS T hese plants are especially adapted for living in ponds, streams, lakes, and rivers—places where other land plants cannot grow. Although aquatic plants belong to many different families, they have similar These species live on the edges of ponds, rivers, and swamps. They are also found in salt marshes, which are periodically adaptations and are therefore an example of adaptive convergence. They include submerged plants and flooded by tides or river overflows. These plants are a transition CATTAILS floating plants; plants that may or may not be rooted at the bottom; amphibious plants, which have leaves between aquatic and land plants. Their limiting factor is the Typha sp. availability of oxygen, so they have well-developed aerenchyma. grow in moist soil, both above and below the water's surface; and heliophilic plants, which have only their roots underwater. around lake margins, and in marshes in both temperate and tropical climates. ARROWHEAD Sagittaria A Vital Role Rooted Plants with Floating Leaves LACHENALIA sagittifolia Lachenalia Its flowers, with three white Aquatic plants play an Such plants are often found in standing or slow-moving water. They have Floating Leaves viridiflora petals and purple stamens, The rhizomes are fixed, the leaves grow on This plant is form during the summer. important role in the ecosystem fixed rhizomes and petiolate leaves (leaves with a stalk that connects to a long stalks, and the leaf surface floats on attractive, with a not only for crustaceans, insects, and stem) that float on the surface of the water. Some of the plants have the water. large number of worms but also for fish, birds, and submerged leaves, some have floating leaves, and some have leaves outside flowers. Upper Epidermis Aquatic plant mammals because they are an the water, with each type having a different shape. In the case of floating Parenchyma with especially important source of food and shelter leaves the properties of the upper surface are different from those of the beautiful flowers. for these categories of animals. lower surface, which is in contact with the water. Aerenchyma Aquatic plants also play a major role in converting solar energy into the PARROT FEATHER TROPICAL WATER LILY Lower Air organic materials upon which many Myriophyllum aquaticum Victoria cruciana Epidermis Conduction Chamber This plant is native to temperate, It grows in deep, calm waters. living things depend. subtropical, and tropical regions, and it Its leaves can measure up to 7 Bundle is highly effective at oxygenating water. feet (2 m) across. YELLOW FLOATING HEART Nymphoides peltata It produces small creased yellow flowers all summer long. KNOTWEED Polygonum sp. This aquatic plant grows Rooted Underwater Plants Aquatic but Modern The roots and in marshy vegetation. Pneumatophores rhizomes under The entire plant is submerged. The small root system SAGO PONDWEED the water are are floating roots that are involved in air serves only to anchor the plant since the stem can directly Potamogeton densus The evolutionary history of plants began in well developed. BLADDERWORT exchange. They take oxygen from the absorb water, carbon dioxide, and minerals. These plants Tbeh ifso wunadte irn pslhaanltlo cwan by meawnas toefr setnrvuicrtounrmese nsutsc.h T ahse yr olaottes.r Mcoondqeurenr aeqdu laatnidc UThtreisceu lcaarrian ivvourlgoaursis sthuerf paclaen, ta nthdr oitu cgihrc iutsla itnetsr atoce tlhluel arrest of ahraev eo fntoe ns yfsotuenmd oinf fsluopwpionrgt —wattheer .w Tahtee rs uhbomldesr ugped t hsete pmlasnt. dcleeparre-sflsoiownisn go fs treams. plants are not a primitive group, however. On the Submerged or Free pthlaenirt sd iceotm wpiltehm semnatll sdpioaxciedse. tToh eeys cparpoeb. aCbelyrt aalisno p alallnotws hcaarvbeo an contrary, they have returned to the water environment aquatic creatures. special adaptation that consists of air by acquiring highly specialized organs and tissues. For Some underwater plants are free, without roots, but sacs that store oxygen for periods when example, some tissues have air pockets that enable the with developed stalks and divided leaves. Other the plant will be submerged or that plant to float. floating plants have a rosette shape and leaves speed up the plant's transpiration. modified for floating; they have well-developed roots HORNWORT with root caps but without absorbent hairs. The roots Ceratophyllum sp. This plant has an help the plant to stay balanced on top of the water. Aerenchyma abundance of fine leaves that form a is always found in floating organisms. This tissue conelike structure has an extensive system of intercellular spaces on each stem. through which gases are diffused. Aerenchyma The underwater parts do not have an impermeable outer layer, so they can absorb Epidermis minerals Air and gases Chamber EELGRASS directly from They produce and Submerged stems have no support system Vallisneria sp. the water. release oxygen as a because the water holds up the plant. Their limiting This oxygenating plant is result of photosynthesis. factor is oxygen availability, so the aerenchyma found in ponds and aquariums. helps make this substance available to the plant.