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Transcript
Chapter 10 Plant Reproduction and Responses Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Co 10 10.1 Sexual Reproduction in Plants • Alternation of generations – Diploid (2n) sporophyte stage • Produces spores by meiosis • Spores divide by mitosis to become gametophytes – Haploid (n) gametophyte stage • Produces gametes by mitosis • Upon fertilization, the cycle returns to 2n sporophyte 10.1 Sexual Reproduction in Plants • In flowering plants, the sporophyte is dominant and it is the generation that bears flowers • Flowers produce two kinds of spores. – Microspores undergo mitosis and becomes a pollen grain, which is the male gametophyte • Pollen grain contains two nonflagellated sperm – Megaspores undergo mitosis to become a microscopic embryo sac, which is the female gametophyte • Female gametophyte is retained within the flower Alternation of Generations in Flowering Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. anther sporophyte seed diploid (2n) ovule ovary zygote FERTILIZATION MEIOSIS haploid (n) microspore egg megaspore sperm Male gametophyte (pollen grain) Female gametophyte (embryosac) 10.1 Sexual Reproduction in Plants • Upon fertilization, a zygote is formed. The zygote develops into an embryo • A seed forms - contains the embryo and stored food • When a seed germinates, a new sporophyte emerges 10.1 Sexual Reproduction in Plants • Parts of a Flower – Sepals - leaf-like structures that protect the developing bud – Petals - attract pollinators – Stamens - male portion of the flower • Anther - produces pollen grains • Filament - a slender stalk that supports the anther – Carpel - female portion of the flower • Stigma - an enlarged stick knob • Style - a slender stalk • Ovary - encloses one or more ovules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. stamen anther carpel (pistil) stigma filament style ovary petal ovule sepal receptacle peduncle 10.1 Sexual Reproduction in Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. stamen • Flower parts occur in threes (or multiples) in monocots s1 p2 carpel s2 p1 petal p3 sepal s3 a. Daylily • Flower parts occur in four or fives (or multiples) in eudicots p3 p2 carpel stamen p4 petal p1 p5 b. Festive azalea a: © Farley Bridges; b: © Pat Pendarvis 10.1 Sexual Reproduction in Plants • Flowers that have sepals, petals, stamens and carpels are called complete flowers – Flowers that do not are called incomplete • A monoecious plant has both staminate and carpellate flowers. • If staminate and carpellate flowers are on separate plants, the plant is dioecious Holly-dioecious 10.1 Sexual Reproduction in Plants • Life Cycle of Flowering Plants – Flowering plants produce: • Microspores • Megaspores 10.1 Sexual Reproduction in Plants • Life Cycle of Flowering Plants – Microspores become mature male gametophytes (sperm-bearing pollen grains) – Megaspores become mature female gametophytes (egg-bearing embryo sacs) 10.1 Sexual Reproduction in Plants • Life Cycle of Flowering Plants – During fertilization, one sperm nucleus unites with the egg nucleus, producing a zygote. – The other sperm unites with the polar nuclei, forming a 3n endosperm cell. 10.1 Sexual Reproduction in Plants • When cell walls form later, there are seven cells, one of which is binucleate • The female gametophyte, also called the embryo sac, consists of these seven cells: – one egg cell; – two synergid cells; – one central cell containing two polar nuclei – three antipodal cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. anther Mature Seed Development of the male gametophyte: In pollen sacs of the anther, a microspore mother cell undergoes meiosis to produce 4 microspores each. seed coat The ovule develops into a seed containing the embryonic sporophyte and endosperm. Development of the female gametophyte: In anovule within an ovary, a megaspore mother cell under goes meiosis to produce 4 megaspores . anther mitosis ovule ovary Pollen sac embryo endosperm (3n) microspore mother cell Sporophyte Seed ovary Ovule megaspore mother cell diploid (2n) MEIOSIS MEIOSIS DOUBLE FERTILIZATION haploid (n) ovule wall tube cell Pollination Microspores During double fertilization, one sperm from the male gametophyte will fertilize the egg; another sperm will join with polar nuclei to produce the 3n endosperm. polarnuclei egg sperm Development of the sporophyte: Pollination occurs; a pollen grain pollen germinates and tube produces a pollen tube. generative cell Megaspores ovule wall Pollengrain (malegametophyte) sperm antipodals Mature male gametophyte tube cell nucleus polarnuclei egg cell synergids Embryosac (mature female gametophyte) (top): Courtesy Graham Kent; (bottom): © Ed Reschke Microspores develop into male gametophytes (pollen grains). One megaspore becomes the embryosac (female gametophyte). megaspore 3 megaspores disintegrate integument micropyle 10.1 Sexual Reproduction in Plants • Pollination – The transfer of pollen from an anther to a stigma • Self-pollination (pollen is from the same plant) • Cross-pollination (pollen is from a different plant) 10.1 Sexual Reproduction in Plants • When a pollen grain lands on the stigma of the same species, it germinates, forming a pollen tube • Pollen tube grows down to micropyle • Double fertilization – One sperm nucleus unites with egg forming 2n zygote – Other sperm nucleus unites with polar nuclei forming 3n endosperm cell Pollinators 10.2 Growth and Development • Development of the Eudicot Embryo – The endosperm cell divides to produce endosperm tissue – The zygote divides into two cells • One cell will become the embryo – Embryonic cells near the suspensor become the root, and those at the opposite end form the shoot • The other cell will give rise to the suspensor – The suspensor pushes the embryo into the endosperm tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. endosperm nucleus zygote endosperm a. b. embryo suspensor basal cell c. cotyledons appearing shoot tip epicotyl bending cotyledons hypocotyl bending cotyledons radicle f. root tip e. d. 10.2 Growth and Development • Monocots Versus Eudicots – Eudicots (two cotyledons) • Cotyledons store nutrients that the embryo uses – Monocots (one cotyledon) • Cotyledon absorbs food molecules from the endosperm and passes them to the embryo 10.2 Growth and Development • Fruit – Derived from an ovary and sometimes other flower parts – As a fruit develops, the ovary wall thickens to become the pericarp • May have up to three layers 10.2 Growth and Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Types of fruit seed covered by pericarp – Simple - derived from a simple ovary of a single carpel or from a compound ovary of several fused carpels • • • • wing a. © James Mauseth Legumes Dry fruits Fleshy fruits Accessory fruits Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b. flesh is from receptacle © Edward S. Ross one fruit 10.2 Growth and Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. one fruit • Fruit Types – Compound fruits develop from several individual ovaries. fruits from ovaries of one flower c. © Runk/Schoenberger/Grant Heilman Photography Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Aggregate fruits • Multiple fruits fruits from ovaries of many flowers one fruit d. © Joe Solem/Riser/Getty Images 10.2 Growth and Development • Dispersal of Seeds – Seeds may have hooks or spines that attach to fur or clothing – Seeds may pass through the digestive tract of animals – Seeds may be gathered and buried by animals – Seeds may be carried by wind or water 10.2 Growth and Development • Germination of Seeds – Some types of seeds remain dormant until conditions are favorable for growth • • • • Temperature Moisture Regulatory Factors (stimulatory and inhibitory) Mechanical Action (examples: water or fire) Doomsday vault seed collection Doomsday vault seed collection Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. plumule (epicotyl with leaves) hypocotyl radicle seed coat cotyledon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cotyledons (two) epicotyl withered cotyledons cotyledons (two) first true leaves (primary leaves) hypocotyl seed coat hypocotyl secondary root primary root primary root © BJ Miller/Biological Photo Service Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. epicotyl plumule (epicotyl with leaves) hypocotyl radicle withered cotyledons cotyledons (two) seed coat cotyledon first true leaves (primary leaves) a. Seed structure hypocotyl seed coat hypocotyl secondary root primary root primary root b. Germination and growth © BJ Miller/Biological Photo Service • Eudicot Versus Monocot Germination – Eudicots – 2 cotyledons • Cotyledons shrivel and degrade • Epicotyl produces immature leaves and is called a plumule • Young shoot is hook shaped as it emerges through the soil Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pericarp endosperm cotyledon coleoptile plumule radicle coleorhiza a. Cornkernel coleorhiza primary root coleoptile © James Mauseth first leaf adventitious root coleoptile Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. true leaf first leaf coleoptile radicle adventitious root coleoptile coleorhiza primary root b. Germination and growth prop root Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pericarp endosperm cotyledon true leaf coleoptile plumule radicle coleorhiza a. Cornkernel coleorhiza primary root first leaf adventitious root coleoptile radicle coleoptile prop root coleorhiza primary root b. Germination and growth b(left): © James Mauseth; b(right): © Barry L. Runk/Grant Heilman Photography – Monocots – 1 cotyledon • Cotyledon does not have a storage function • Plumule and radicle are protected by coleoptile and the coleorhiza • Plumule and radicle burst through the sheaths when germination occurs