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Chapter 27: pp. 493 - 509 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10th Edition Sylvia S. Mader Flowering Plants: Reproduction BIOLOGY © Royalty-Free/Corbis PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display 1 2 Reproductive Strategies • All plants have a two-stage, alternating life cycle (alternation of generations) • Sporophyte produces haploid spores by meiosis • Spores divide mitotically to become haploid gametophytes • Gametophytes produce gametes • Gametes fuse to produce zygote • Zygote divides mitotically to become diploid sporophyte 3 Alternation of Generations in Flowering Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 8 anther 1 7 sporophyte seed 2 diploid (2n) 6 zygote FERTILIZATION ovule ovary MEIOSIS haploid (n) 3 egg sperm 5 Male gametophyte (pollen grain) Female gametophyte (embryo sac) microspore megaspore 4 4 Reproductive Strategies Flowers are the reproductive structure (aka genitalia) of the plant and produces two types of spores Microspore - Male gametophyte Pollen Megaspore - Female gametophyte Embryo within the ovary LE 38-2A Anther Stamen Filament Stigma Carpel Style Ovary Sepal Petal Key Haploid (n) Diploid (2n) Receptacle An idealized flower LE 38-2B Germinated pollen grain (n) (male gametophyte) Anther Ovary Ovule Embryo sac (n) (female gametophyte) Pollen tube FERTILIZATION Egg (n) Mature Sperm (n) sporophyte plant (2n) Zygote (2n) Seed Key Seed Haploid (n) Diploid (2n) Germinating seed Simplified angiosperm life cycle Embryo (2n) (sporophyte) Simple fruit 7 Flowers • Sepal- green “petals” that protect bud • Petal- colorful “leaves” • Stamens- male part • Anther - Saclike container • Filament - Slender stalk • Carpel- female part • Stigma - Enlarged sticky knob • Style - Slender stalk • Ovary - Enlarged base enclosing ovules 8 Pollination • Pollination is the transfer of pollen from an anther to the stigma of a carpel • Self-pollination occurs if the pollen is from the same plant • Cross-pollination occurs if the pollen is from a different plant Some plants have ways to prevent self pollination. 9 Pollination Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. 118 mm c. 8 mm a: © George Bernard/Animals Animals/Earth Scenes; b: © Simko/Visuals Unlimited; c: © Dwight Kuhn 10 Pollinators Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. Aa: © Steven P. Lynch; Ab: © Robert Maier/Animals/Animals/Earth Scenes 11 Pollinators Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. Ba: © Anthony Mercieca/Photo Researchers, Inc.; Bb: © Merlin D. Tuttle/Bat Conservation International; 12 Fertilization • When pollen grain lands on stigma, it germinates forming a pollen tube • Passes between the stigma and style to reach the micropyle of the ovule • Double fertilization occurs • One sperm nucleus unites with the egg nucleus, producing a zygote • Other sperm nucleus unites with the polar nuclei, food storage endosperm double fertilization animation LE 38-6 Pollen grain Stigma Pollen tube If a pollen grain germinates, a pollen tube grows down the style toward the ovary. 2 sperm Style Ovary Polar nuclei Ovule (containing female gametophyte, or embryo sac) Egg Micropyle Ovule Polar nuclei The pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule. One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryo sac’s large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm. Egg Two sperm about to be discharged Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n) (egg plus sperm) From Ovule to Seed • After double fertilization, each ovule develops into a seed • The ovary develops into a fruit enclosing the seed(s) 15 Monocot vs. Eudicot Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. seed coat plumule pericarp hypocotyl endosperm coleoptile radicle cotyledon embryo plumule cotyledon radicle coleorhiza a. b. a: © Dwight Kuhn; b: Courtesy Ray F. Evert/University of Wisconsin Madison embryo 16 Fruits Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Drupe True Berry exocarp chamber of ovary has many seeds pericarp exocarp (skin) mesocarp (flesh) endocarp (pit contains seed) a. A drupe is a fleshy fruit with a pit containing a single seed produced from a simple ovary. b. A berry is a fleshy fruit having seeds and pulp produced from a compound ovary. Samara Legume seed covered by pericarp wing pericarp seed c.A legume is a dry dehiscent fruit produced from a simple ovary . d. A samara is a dry indehiscent fruit produced from a simple ovary . Aggregate Fruit Multiple Fruit fruit from many ovaries of a single flower e. An aggregate fruit contains many fleshy fruits produced from simple ovaries of the same flower. one fruit fruits from ovaries of many flowers f. A multiple fruit contains many fused fruits produced from simple ovaries of individual flowers. a, b: © Kingsley Stern; c: © Dr. James Richardson/Visuals Unlimited; d: © James Mauseth; e: Courtesy Robert A. Schlising; f: © Ingram Publishing/Alamy Seed Germination • As a seed matures, it dehydrates and enters a phase called dormancy • Seed dormancy increases the chances that germination will occur at a time and place most advantageous to the seedling • The breaking of seed dormancy often requires environmental cues, such as temperature or lighting changes From Seed to Seedling • Germination depends on imbibition, the uptake of water due to low water potential of the dry seed • The radicle (embryonic root) emerges first • Next, the shoot tip breaks through the soil surface • In many eudicots, a hook forms in the hypocotyl, and growth pushes the hook above ground • Time lapse fast growing corn LE 38-10A Foliage leaves Cotyledon Epicotyl Hypocotyl Cotyledon Cotyledon Hypocotyl Hypocotyl Radicle Seed coat Common garden bean 20 Simple Fruits Dispersal Many seeds are dispersed by wind Woolly hairs, plumes, wings Fleshy fruits - Attract animals and provide them with food Peaches, cherries, tomatoes Accessory fruit - Bulk of fruit is not from ovary, but from receptacle Apples 21 Fruit Dispersal by Animals Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. a: © Marie Read/Animals Animals/Earth Scenes; b: © Scott Camazine/Photo Researchers, Inc.