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Transcript
Parts of a Flower Plants grow is every part of the world- mountaintops, oceans, deserts, and Polar Regions. Without plants there would be no life on earth. They provide the air we breathe and the food humans and other animals eat. Plants also supply us with many useful products (something that comes from the consequence of something else.) such as lumber for wood and paper and cotton fibers for clothes. Scientist believe there are more than 350,000 species (individuals that may resemble (look like) one another). Their size varies from barely visible plants that grow on a forest floor to the largest living life forms on Earth like the giant sequoia trees of California. Giant sequoia trees Plants are also the oldest living things on Earth. One kind of pine tree in California called the bristlecone pine started growing 4,000-5,000 years ago. Bristlecone pine trees Today for Science Lab will be observing the part of the plant called the flower. Flowers are the part of a plant that makes seeds. PARTS OF A FLOWER A flower has two special parts that help the flower make seeds. These two special parts are the male stamen and the female carpel. A stamen has two parts to it, the A anther or pollen box and the filament. The carpel has three important parts. At the top is a sticky tip called the stigma. The long stem is called the style. At the very bottom is the ovary. The ovary has eggs in it that can grow into seeds. A pollen grain needs to join with each egg to form a seed. Most flowering plants need to get pollen from another plant. This is called cross-pollination. In some flowering plants, the pollen grains are blown from one plant to another by the wind. Grains such as wheat, rice, corn oats, and barley have flowers that are pollinated by the wind. Wheat Plants Some flowers are pollinated by insects. These flowers often have bright colors and sweet nectar to attract insects such as bees or butterflies. When the insect visits a flower, the pollen sticks onto its body. When the insect visits another flower, the pollen brushes off onto the sticky stigma of the flower. Bee collecting pollen from flower Some flowers can grow fruit and seeds without being pollinated at all. Dandelions plants can grow fruit and seeds without being pollinated. Dandelion Flowers pollinated by butterflies usually bloom in later summer when the butterflies are around. Flowers that have a strong scent or smell in the evening such as honeysuckle are pollinated by night –flying moths. Honeysuckle flower Yucca plant and flower So are a number of pale flowers, such as the yucca flower. Growing seeds and fruit What happens when the pollen grain gets onto the sticky stigma? If the pollen grain comes from a different kind of plant, nothing happens. But if the pollen comes from the same kind of flowering plant, then two things happen. First, part of the pollen grain grows a tube down through the stigma and style to the ovary, where the egg is. Then the center part of the pollen grain goes down the tube and joins with the egg. This joining is called fertilization. A seed can now form. Some flowers, such as apple, pear, and strawberry flowers have many stigmas in each flower and so have many ovaries. If pollen grains stick to each stigma, then several seeds will grow inside the apple or fruit. Apple blossoms Apple fruits with seeds All flowering plants have fruit. Plants such as daffodils and roses have fruit but it is not the kind of fruit we eat. While the seeds and fruits are growing, the sepals, petals, and stamen of the flower die. On some fruit such as apples, pears, and string beans, you can see the shriveled –up sepals, petals or stamens on the end of the fruit. Can you see the dead flowers on the ends of these apples? PARTS OF A FLOWER LAB Teachers: Read directions to students when they begin the lab Procedure: Objective: Students will identify the parts of a flower to discover where seeds originate. Materials: Complete flower Flower Dissection Instructions (one set per tray) and Parts of a Flower Data Sheet (One per student) Clear tape ( one roll per tray) Magnifier Cut apple (one per tray) How Flowers Reproduce Diagram (One per tray) Activity: Inform students that they are going to dissect (take apart) a flower to see where seeds are formed. Students follow the instructions on the data sheets to dissect their flowers (one flower per two students). Complete the data sheet. When the data sheet is complete have students read the information of the How Flowers Reproduce work sheet. Parts of a flower Data Sheet: Directions: Tape or draw (Since there is just one stamen one students should draw that stamen and the other student tape the stamen in the correct box.) the parts of a flower in the correct boxes below then complete the information. Stem Description: Magnified view of the tip of the stem Sepal Number of sepals:__________________ Description of how it feels: Petal: Describe fragrance: Pollen: Describe how it feels: Number of petals:__________________ Why do flowers have colored petals and sometimes have a fragrance? Magnified view of pollen grains: Stamen: Number of stamens:__________________ Describe what you saw on the anther: Pistil: Number of pistils:___________________ Describe how the stigma feels: Magnified view of anther: Magnified view inside ovary: How Flowers Reproduce 1. Each pollen grain is a single cell. Pollen forms on the top (anther) of the stamen. 2. Pollen is carried by insects, wind, or birds to the stigma, the sticky part top of the plant. 3. Once on the stigma, the pollen grain absorbs moisture from the pistil and breaks open. 4. Its contents form a pollen tube, growing down the pistil. 5. The pollen tube grows until it reaches the ovule containing an egg cell. 6. Sperm from the pollen travels down the tube to the ovule and unites with the egg cell. 7. A seed now begins to develop inside the ovary. 8. An ovary may have a single seed or more than one seed. 9. The ovary develops into a fruit enclosing the seed(s).