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Name Class CHAPTER 5 Date Plant Processes 1 Photosynthesis SECTION National Science Education Standards BEFORE YOU READ After you read this section, you should be able to answer these questions: LS 1a, 1c, 3c, 4c • How do plants make food? • How do plants get energy from food? • How do plants exchange gases with the environment? What Is Photosynthesis? Many organisms, including humans, have to eat to get energy. Plants, however, are able to make their own food. Plants make their food by a process called photosynthesis. During photosynthesis, plants use carbon dioxide, water, and energy from sunlight to make sugars. STUDY TIP Outline As you read, outline the steps of photosynthesis. Use the questions in the section titles to help you make your outline. How Do Plants Get Energy from Sunlight? Plant cells have organelles called chloroplasts. Chloroplasts capture the energy from sunlight. Inside a chloroplast, membranes called grana contain chlorophyll. Chlorophyll is a green pigment that absorbs light energy. Many plants look green because chlorophyll reflects the green wavelengths of light. The grana in chloroplasts contain chlorophyll. Chlorophyll is a pigment that absorbs sunlight. Plant cell Chloroplast READING CHECK 1. Define What is chlorophyll? Grana Chloroplasts TAKE A LOOK 2. Identify Where is chlorophyll found in a plant cell? Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 67 Plant Processes Name SECTION 1 Class Date Photosynthesis continued How Do Plants Make Sugar? READING CHECK 3. Identify What are two products of photosynthesis? During photosynthesis, plants take in water and carbon dioxide and absorb light energy. Plants use the light energy captured by chlorophyll to help form glucose molecules. Glucose is the sugar that plants use for food. In addition to producing sugar, plants give off oxygen during photosynthesis. The following chemical equation summarizes photosynthesis: 6CO2 + 6H2O (carbon dioxide) light energy (water) C6H12O6 (glucose) + 6O2 (oxygen) Light energy Carbon dioxide Oxygen Sugar is made in the leaves. STANDARDS CHECK LS 1c Cells carry on the many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to provide energy for the work cells do and to make the materials that a cell or an organism needs. 4. Identify Which cell structures release the energy stored in sugar? Water During photosynthesis, plants take in carbon dioxide and water and absorb light energy. They make sugar and release oxygen. How Do Plants Get Energy from Sugar? Glucose molecules store energy. To use this energy, a plant cell needs its mitochondria to break down the glucose. This process of breaking down food molecules to get energy is called cellular respiration. During cellular respiration, cells use oxygen to break down food molecules. Like all cells, plant cells then use the energy from food to do work. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 68 Plant Processes Name SECTION 1 Class Date Photosynthesis continued How Does a Plant Take in the Gases It Needs? Plants take in carbon dioxide and give off oxygen. These gases move into and out of the leaf through openings called stomata (singular, stoma). Stomata allow gases to move through the plant’s cuticle, the waxy layer that prevents water loss. Each stoma is surrounded by two guard cells. The guard cells act like double doors by opening and closing a stoma. Water vapor also moves out of the leaf through stomata. The loss of water from leaves is called transpiration. Stomata open to allow carbon dioxide to enter a leaf. They close to prevent too much water loss. Critical Thinking 5. Predict What do you think would happen if a plant had no stomata? Cuticle Vascular tissue TAKE A LOOK Stoma CO2 enters through stoma. 6. Identify Circle the guard cells in this picture. What is their function? Cuticle H2O and O2 exit through stoma. Why Is Photosynthesis Important? Plants, along with many bacteria and protists that also use photosynthesis, form the bases of most food chains on Earth. During photosynthesis, plants store light energy as chemical energy. Animals get this energy when they eat plants. Other animals get energy from plants indirectly. They eat the animals that eat plants. Most organisms could not survive without photosynthetic organisms. Photosynthesis is also important because it produces oxygen. Recall that cellular respiration requires oxygen to break down food. Most organisms, including plants and animals, depend on cellular respiration to get energy from their food. Without the oxygen produced during photosynthesis, most organisms could not survive. Say It Describe Think of all the ways in which photosynthesis is important to you. Describe to the class three ways you depend on photosynthesis. READING CHECK 7. Complete During photosynthesis, plants store light energy as . Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 69 Plant Processes Name Class Section 1 Review Date NSES LS 1a, 1c, 3c, 4c SECTION VOCABULARY cellular respiration the process by which cells use oxygen to produce energy from food chlorophyll a green pigment that captures light energy for photosynthesis photosynthesis the process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to make food stoma one of many openings in a leaf or a stem of a plant that enable gas exchange to occur (plural, stomata) transpiration the process by which plants release water vapor into the air through stomata; also the release of water vapor into the air by other organisms 1. Explain Why does chlorophyll look green? 2. Identify What is the role of mitochondria in plants? In what process do they take part? 3. Compare Complete the chart below to show the relationship between photosyn- thesis and cellular respiration. Photosynthesis Cellular respiration Cells break down food to provide energy. Oxygen is produced. 4. Identify What two structures in plant leaves help prevent the loss of water? 5. Explain Why are photosynthetic organisms, such as plants, so important to life on Earth? 6. Explain If plants need to take in carbon dioxide, why don’t they keep their sto- mata open all the time? Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 70 Plant Processes A Microorganisms, Fungi, and Plants Answer Key continued 2. fertilization 3. Clockwise from top left: young plant, seed 4. 5. 6. 7. 8. 6. Both have vascular tissue. 7. A growth ring shows a period of growth and a coat, cotyledon Seeds can store food for the young plant, but spores cannot. Seeds can be spread more efficiently than spores. by wind sexual reproduction—the joining of egg and sperm 89% Monocots Dicots flower parts in threes flower parts in fours or fives leaves with parallel veins leaves with branching veins one cotyledon two cotyledons bundles of vascular tissue scattered bundles of vascular tissue in a ring 8. 9. 10. 11. 12. 13. 14. 15. 16. Review 1. Clockwise from top: petal, stigma, style, ovary, ovule, sepal, filament, anther 2. Taproot systems have one main root that can get water from deep underground. Fibrous root systems have many small roots that get water from close to the soil surface. 3. Stems support the body of a plant; allow for transport of water, minerals, and food; and store materials for the plant. 4. roots, stems, leaves, flowers 9. in a fruit 10. by wind Review 1. The gametophytes of seed plants live inside 2. 3. 4. 5. 6. dormant period. The cycle repeats each year, so the number of growth rings should show the number of years the tree has been growing. The vascular tissues are arranged differently. photosynthesis Vascular—it has xylem and phloem. angiosperms Top to bottom: petal, sepal anther and filament stigma, style, ovary stamen Top to bottom: stigma, style, ovary, ovule, pistil the sporophytes. The gametophytes of seedless plants live as separate plants. Pollen is transferred from a male part of a plant to a female part. Gymnosperms: Seeds develop in cones; they don’t have flowers. Angiosperms: Seeds develop in fruits; they have flowers; pollen can be carried by animals. Both: They produce seeds; they are vascular; pollen is carried by the wind. The seed coat protects the growing plant. Cotyledons provide food for the growing plant. The young plant/sporophyte grows into an adult plant. a cone flowers and fruits Chapter 5 Plant Processes SECTION 1 PHOTOSYNTHESIS a green pigment that absorbs light energy in the grana of chloroplasts glucose and oxygen mitochondria The plant couldn’t take in carbon dioxide. It couldn’t make food. 6. Circles should be around the structures on the sides of the stoma; they open and close stomata. 7. chemical energy 1. 2. 3. 4. 5. SECTION 4 STRUCTURES OF SEED PLANTS 1. roots, shoots, reproductive structures 2. Xylem carries water and minerals; phloem Review 1. It reflects the green wavelengths of sunlight. 2. Mitochondria break down food to provide carries food to all parts of the plant. 3. Xylem moves the water and minerals through the plant. 4. in the center of the root 5. A stem is an organ that connects the roots to leaves and reproductive structures. energy. They take part in cellular respiration. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook Answer Key 5 Microorganisms, Fungi, and Plants A 3. Microorganisms, Fungi, and Plants Answer Key continued Photosynthesis Cellular respiration Cells make food for the plant. Cells break down food to provide energy. Oxygen is produced. Oxygen is used to break down food. 4. very cold weather, very dry weather 5. plantlets, tubers, runners 6. Plants need roots first so they can start to get nutrients from the soil. Also, the roots hold the plant in place. 4. stomata and cuticle 5. They form the base of almost all food chains SECTION 3 PLANT RESPONSES TO THE ENVIRONMENT on Earth. They also produce oxygen, which most organisms need for cellular respiration. 6. They would lose too much water. 1. anything that causes a reaction in your body 2. The X should be on the right side of the SECTION 2 REPRODUCTION OF FLOWERING PLANTS 3. 4. 1. stigma 2. ovule 3. Seeds are fertilized ovules. Fruits are ovaries 4. 5. 6. 7. 8. 5. 6. 7. that have grown larger to protect the seeds. The ovules should be circled. Protect the seed and spread seeds to new environments. if conditions were not right for a new plant to grow the root If no other plant of the same species were available for pollination, a plant could still reproduce, asexually. picture. A plant will grow toward light. Arrow points down. It must have been growing upside down. Plant stems grow away from gravity. 7.2 h chlorophyll orange and yellow pigments Review 1. A negative tropism is growth away from 2. 3. 4. 5. Review 1. Sexual—it involves the joining of a sperm and an egg. 2. In pollination, pollen lands on the stigma. In fertilization, a sperm joins with an egg. 3. A mature plant produces flowers. Flowers are pollinated. Eggs are fertilized. The ovary becomes a fruit, and ovules become seeds. Seeds are spread. They sprout and grow into new plants. 6. 7. a stimulus. A positive tropism is growth toward a stimulus. Cells farthest from the light grow longer than cells facing the light. This causes the shoot to bend toward the light. plant growth in response to gravity change in the length of days Short-day plants need short days and long nights in order to start reproducing. Long-day plants need longer day lengths to reproduce. Chlorophyll hides the other pigments in the summer. Evergreen leaves are covered with a thick cuticle that protects them from cold and dry weather. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook Answer Key 6 Microorganisms, Fungi, and Plants