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Transcript
Science of Life Explorations Plant Anatomy: What Makes a Plant a Plant? What do you know about plants? We’re going to take a closer look at the anatomy of plants we have in our gardens and fields. ANATOMY is a science of the structure of an animal or plant or one of its parts. The plants we have in our neighborhoods generally have three major traits in common. They have roots, stems and leaves. There are other types of plants like primitive mosses and ferns whose plant parts are not so easy to recognize. Did you know that cacti do not have leaves! Their thick, padded stems do the work of leaves! What makes a plant a plant? What are three important plant parts? How do plant roots work? What is a stem? Why do plants have leaves? What makes a plant a plant? The ability to make their own food energy! Plants have a lot of variety and can appear to be very different because they are adapted to many different environments. One of these below is a tropical plant and prefers heat, humidity and wet soil. One is found in very hot, dry environments and doesn’t have leaves. Choose one of the plants below and describe how it appears to be the same or different than the others. ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ _______________________________________ _______________________________ ____ In general, most plants have roots, leaves and stems. Have you ever looked at plants and noticed the TRAITS that they share? The next time you are outside, compare plants you find in vegetable gardens, flower gardens, parks or fields. Look at small plants, shrubs and trees. Let’s think about plants that you could find in your yard or garden or neighborhood. What are three important plant parts to consider? 1._______________________________ 2._______________________________ 3._______________________________ Of these three, do you think one is more important than the others, or do you think they are equally important? _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ In our soil lessons, we talked about how water, nutrients and air in the soil are needed by plants. Roots have many ESSENTIAL roles. They support the plant, keeping it in the soil. They take in water and nutrients from soil. Much of the food energy created by leaves is stored in the plant’s roots. Even when plants appear to be dead or DORMANT in the winter, plant roots are hard at work! When plant roots are injured or exposed to diseases or other pests, the plant suffers. What is a stem? The very first thing that grows out of a seed is the root. It grows down through soil. Next comes a shoot. That shoot becomes the main stem of the plant. In the case of some plants, like corn, that stem will get bigger around and taller but will never make new stems or branches. In the case of other plants, that stem will become sturdier and produce branches. The main stem of some plants may grow large but stay green. The main stem of other plants grows tough and woody and then we call it a TRUNK! When planting, be careful that you do not injure the stem or trunk of the plant. For Example, although tree trunks seem tough, they can be damaged. Give the roots plenty of space to spread out in soft soil for best results. 1. outer bark 2. PHLOEM - a layer of cells that carry food energy from the leaves to the roots 3. CAMBIUM - a layer of cells that produces new growth of phloem and xylem cells each year, causing the tree to grow larger. 4. XYLEM - a layer of cells that carries water and nutrients from the roots to Reproduced by permission of Morton Publishing from the leaves. Van De Graaff and Crawley, A Photographic Atlas for the Biology Laboratory, 5th Edition. © 2005 Why do plants have leaves? Leaves do the major work of PHOTOSYNTHESIS. Leaves gather sun energy and CARBON DIOXIDE. They also release water vapor and OXYGEN. Inside the leaf, plant cells are using carbon dioxide, sun energy, water and nutrients to create food energy for the plant. Plant leaves VARY greatly. They all have the purpose of collecting sun energy, carbon dioxide and water. Look closely and you’ll see that leaves can be light green, dark green, yellow, thin, thick, fuzzy, smooth, sharp-edged, smooth-edged, round, pointed, large or small. They can come in groups of one, two, three, or many more. Some leaves are so different, we call them needles. This is a great time to take a walk outside and examine the leaves of many types of plants. You may even have house plants. Don’t forget the leaves of vegetables and fruits! Compare the leaves below. Do you recognize any of these plants? Leaves are famous for one other thing, aren’t they? They fall! Actually, not all leaves fall, but many do. Most fallen leaves come from plants called BROADLEAF plants. The National Arbor Society likes to consider trees to be in two categories: BROADLEAF or CONIFER. Conifers generally have NEEDLES. Circle the plant above that has needles instead of a ‘broadleaf’. Plant Anatomy Review: Plants are unique because they have the ability to make their own food energy! Most plants have roots, stems and leaves. These plant parts do the same types of work, but they may vary quite a lot. Plant roots work all year long to collect water and nutrients. They store energy. We don’t usually see plant roots, but when they are injured or exposed to diseases, the plant will have problems, too. Plant leaves can be many shapes, sizes and thicknesses. When people talk about shrubs and trees, they may separate them into groups called broadleaf plants and conifer plants. Conifers usually have needles. Needles are special leaves that usually stay on the plant all year long. Because of this, many people call them evergreens. Test Yourself! 1. When comparing plants look at their three main traits. List them here: ______________, __________________, ________________ 2. Plants are unique because they are able to make their own _________________________________ 3. What is one job of the roots seen in this illustration? ___________________________________________________________ ___________________________________________________________ ______________________________ ______________________________ ______________________________ ______________________________ Vocabulary anatomy - the science that deals with the structure of an animal or plant or one of its parts angiosperm - the scientific name for plants that produce flowers as part of their life cycle annual - plants that survive one growing season in a particular area broadleaf - the term for plants that have broad leaves rather than needles cambium- a layer of cells under bark and phloem; new cells are formed along this layer which cause the plant to grow larger each year carbon dioxide - a gas in our atmosphere that plants use to make their own food energy; animals exhale carbon dioxide into the air chloroplasts - an important part of plant cells that enables plants to create food energy for themselves in the process of photosynthesis circumference - the measurement of something all the way around it conifer - a term for plants that produce narrow needle-like leaves rather than broad leaves consumers - animals or people that acquire (eat, buy, take) products created by others cotyledon - the first and very important leaf or leaves of flowering plants crown - a tree crown is all the branches and leaves of the tree; a plant crown is the base of the plant at ground level, above the roots and the source of new leaf growth deciduous - the term for woody plants that drop their leaves before winter dicot - the term for a flowering plant which produces two leaves on its shoot and will develop branches and leaves when mature dormant - for plants, this means active growth stops due to a change in season essential -something that is very important and needed estimate - a good guess or calculation of something based on the information you can gather about it evapo-transpiration - the way that plants release water back into the soil through their leaves; it is a form of evaporation when water changes into a vapor evergreen -the general term used for plants that don’t lose their leaves; most are conifers, but not all gymnosperm - the scientific name of plants that don’t produce flowers but create seed-bearing cones instead herbaceous - plants that do not produce a woody covering to their stems and generally die back in the winter monocot - plants that send up one shoot and one new leaf only, and will mature to have only one stem needles - the name for the narrow ‘needle-like’ leaves of conifers oxygen - the gas found in our atmosphere that animals must inhale to to nourish their cells and stay alive; plants release oxygen perennial - plants that complete a life cycle in one season and resume growth again for more than one year phloem - phloem is the part of plants that transports food energy from leaves down to the roots. photosynthesis - the way plants create their own food energy protista - the scientific kingdom that includes fungi, molds, algae and other organisms shrub - similar to a tree but usually has more than one woody stem stem - the stalk or trunk of a plant; there can be one or many stems on a plant trait - a quality of or a feature of something that stays constant trunk - the woody stem of some plants, especially shrubs and trees turf - grass that is grown and maintained to be a lawn or outdoor use area unique - one of a kind; not like others vary - to show variety or differences vascular bundles - plant tissue that acts as waterways to move food energy, nutrients and water throughout the plant veins - tube-like structures which allow water and sugars to travel through plants or in the case of animals, blood to the heart woody - a plant that has bark over its stem rather than soft green tissue xylem - xylem is the part of a plant that transports water and nutrients up to leaves For Teachers and Parents During many previous lessons we have often touched on the ways plants are an intricate part of our lives. We hope that somewhere near your school, you have an area to take your students for a walk sometime during this lesson. Even the smallest houseplant would be a good place to start. Plants are about as diverse as they can be and are so much a part of our lives that we tend to take them for granted. After all, the photosynthetic quality of plants enables us to have a renewable source of oxygen. Plants offer shade, food, oxygen and more. Reconnecting with the natural world happens quickly for students when they can examine plants directly. This lesson starts with some plant basics: Almost all plants have roots, stems and leaves. This may surprise you. Don’t all plants have leaves? No. Cacti use their thickened stems to do the work of leaves! These three major plant parts are the focus of any study of plants. But what makes plants so unique? They are capable of creating their own food energy. The rest of us are consumers. Even mushrooms, once considered plants, can not use photosynthesis. Plants are the basis for almost any food chain. As students learn about the roots, stems and leaves of plants, they will also be exposed to the many ways plants are different from one another. Plants are broken down into smaller groups by comparing the way they grow and reproduce. This lesson offers some of those comparison: Some plants have flowers and fruit in their life cycles (angiosperms) while others use rudimentary flowers and cones (gymnosperms) Some plants start out with one leaf (monocot) and others with two (dicot) and mature to be very different types of plants Some plants have broad leaves (broadleaf) and some have needle leaves (conifer) Some plants drop their leaves (deciduous) and some don’t (evergreen or conifer) Some plants have stems that stay green (herbaceous) and some develop bark (woody) Students will have opportunities to measure the size of trees, compare leaves and consider how plants and people interact with the air around us (the carbon dioxide and oxygen cycles). It will surprise many students to consider the vast ways we eat plants other than having vegetables on our plates! The plant anatomy lesson will touch on many subjects discussed in prior lessons and reinforce them. Like animals, plants have a way of helping humans remember they are part of a large interactive environment. We hope the plant anatomy unit increases interest in plants for your students. A major part of IPM, integrated pest management is to learn about the life cycles and biology of what we are dealing with. Basic plant knowledge is a good start. Pg 1 This lesson contains many references to the ways plants are the same, and different. The essential questions listed are a good start for class discussion. Throughout these lesson activities, any opportunity to examine live plants is beneficial. Pg 2 The four plants illustrated here are a water-loving tropical plant, a cactus plant, a sunflower, and the branch of a shrub showing fruits. Students are asked to compare one of these plants with the others. They may consider the locations where the plant grows. Presence of fruit or seeds or flowers, shapes, textures, colors and use. Because these plants are representative only, this writing exercise is not meant to examine facts but to encourage thought. Pg 3 All plants reproduce by some means, but remind students that not all plants have flowers. We will discuss plant life cycles in the next lesson. One focus of this lesson is to reinforce to students that plants use roots, stems and leaves to do their most important job - photosynthesis. Throughout the previous lessons, we’ve discussed the importance of water, soil, and sun energy to plants, and how plants interact in our world as food, shelter and beauty to animals and humans. Have students think back and explain, in writing, one way plants use roots, stems or leaves to function and survive. Pg 4 When plants are young, they can lose some of their roots, and some of their leaves, but not too many can survive the loss of their stem. We will discuss later how some plants have one stem, such as a tree, and some have multiple stems, such as a shrub. Perennial plants that have well-established roots can grow new stems. The illustration of the layers of tissue under tree bark introduces some large words, but we don’t expect students to learn these words. The concept here is plants have stems with active layers or waterways that move water and nutrients and sugars (self-made food energy). Most students will know that in woody stems, each years’ growth adds a ring of tissue. Pg 5 This is a great time to explore the outdoors and collect leaves. Another option is to have students design a leaf of their own and describe the plant it came from. Remind students that leaves tend to be symmetrical. Test Yourself! 1. When comparing plants look at their three main traits. List them here: roots stems leaves ______________, __________________, ________________ 2. Plants are unique because they are able to make their own food, energy or food energy _________________________________ 3. What is one job of the roots seen in this illustration? gather nutrients, gather water, ___________________________________________________________ store energy, keep plant firmly in soil, etc ___________________________________________________________