Slide 1 Sexual Reproduction in Plants Slide # 2 Flower Structure Stigma Ovary Fruit Style Ovule Seed Anther Filament Ovule Petal Sepal Pistil (female Part) Stigma Style Ovary Receptacle Stamen (Male Part) Anther Filament Ovary Slide # 3 Structure of a Flower 1.Pistil:female reproductive structure a.Stigma: sticky tip; traps pollen b.Style: slender tube; transports pollen from stigma to ovary c.Ovary: contains ovules; ovary develops into fruit d.Ovule: contains egg cell which develops into a seed when fertilized Stamen Anther Filament Ovule Stigma Pistil Style Ovary Petal Sepal Slide # 4 Structure of a Flower 2.Stamen: male reproductive structure a.Filament: thin stalk; supports anther b.Anther: knob-like structure; produces pollen c.Pollen: contains microscopic cells that become sperm cells Stamen Anther Filament Ovule Stigma Pistil Style Ovary Petal Sepal Slide # 5 Slide # 6 Perfect & Imperfect Flowers Perfect Flower ~ has pistil & stamen Imperfect Flower ~ only one sex Slide # 7 Structure of a Flower 3.Sepals: encloses & protects flower before it blooms Stamen Anther Filament Stigma Pistil Style Ovary 4.Petals: usually colorful & scented; attracts pollinators Ovule Petal Sepal Slide # 8 Slide # 9 Pollination The transfer of pollen grains from the anther to the stigma. Pollination may be aided by wind, insects, and birds. In some instances, the colored petals act as a visual attractant for insects. If pollination occurred in a dry environment, the pollen would not dehydrate (dry up) due to a thick wall that surrounds it. Two types of pollination: 1. Self-Pollination 2. Cross-Pollination Slide # 10 Self-Pollination The transfer of pollen grains from the anther to the stigma of the same plant. Cross-Pollination The transfer of pollen grains from the anther of a flower on one plant to the stigma of a flower on a different plant. Allows for variations due to the combination of two different plants. Slide # 11 Following pollination, the pollen grain germinates to the stigma and forms a pollen tube. Pollen tube is an adaptation for internal fertilization. 2 Haploid sperm cells travel down the pollen tube and only one fertilizes the egg in the ovule. Slide # 12 Fertilization and Embryo Development The union of a sperm cell and an egg cell results in the formation of a zygote The zygote undergoes development resulting in the formation of an embryo (ripened ovule) The ripened ovule (embryo) develops into the seed The ripened ovary develops into the fruit Slide # 13 Structure of a Seed (embryo) Hypocotyl: Develops into roots and in some species lower stem. Radical: Develops in roots Epicotyl: Develops into leaves and upper stem Cotyledon: Stored food for early development of embryo (seed leaves) Slide # 14 Structure of a Seed Epicotyl Slide # 15 Seed coat: • forms from outer layer of ovule • protects embryo Endosperm: food storage tissue (the other sperm creates this triploid (3n) structure when it fertilizes 2 polar bodies from oogenesis) Slide # 16 Monocots & Dicots Monocots – seeds with one cotyledon (corn) Dicots – seeds with two cotyledons (bean, peanut) Slide # 17 Germination and Growth Fruits are specialized structures which aid in seed dispersal. Seeds develop inside the fruit. If the temperature and moisture levels are sufficient, the dispersed seeds will germinate (activate and grow). Growth in most plants occurs in the meristems. The organs of a plant are developed in the meristems. Apical Meristems are found in the tips of roots and stems and cause the plant to grow in height. Lateral Meristems are between the xylem and phloem and cause the plant to grow in diameter (get wider). Slide # 18 Plant Responses and Adaptations Slide #19 Hormone Action on Plants A. Plant cells can produce hormones (chemical messengers that travel throughout the plant causing other cells called target cells to respond) B. In plants, hormones control: Movement of hormone Hormoneproducing cells Target cells 1. Plant growth & development 2. Plant responses to environment Cells in one blooming flower signals other blooms using hormones to open. Slide # 20 Plant Hormones Auxin High Auxin ~ stimulates stem growth ~ inhibits root growth Low Auxin ~ reverse effect Gibberellin • Increases stem growth • Increases fruit and seed development Slide # 21 Plant cells will send signals to one another to tell them: 1. When trees to drop their leaves. 2. When to start new growth. 3. When to cause fruit to ripen. 4. When to cause flowers to bloom. 5. When to cause seeds to sprout. Tree Budding Fruit Ripening Cactus Blooming Leaf Drop Sprouting Corn Seeds Slide # 22 Ethylene causes Fruit to Ripen 1.Fruit tissues release a small amount of ethlyene 2. Ethylene is a gaseous hormone 3.Causes fruits to ripen 4.As fruit become ripe, they produce more and more ethlyene, accelerating the ripening process Ethylene released by apples and tomatoes causes fruit to age quickly. Slide # 23 Plant Tropisms Tropism: the way a plant grows in response to stimuli in the environment caused by an unequal distribution of auxin. Phototropism: growth response to light -Plants bend towards light Geotrophism: growth response to gravity -plant roots grow down with gravity, shoots (stems) grow up against gravity and out of the soil. Thigmotropism: growth response to touch -vines grow up around trees, venus flytrap closes when leaves are touched Slide # 24 What type of tropism is shown in these pictures?