video slide - Biology Junction

video slide - Biology Junction

Chapter 38 Angiosperm Reproduction and Biotechnology PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: To Seed or Not to Seed The parasitic plant Rafflesia arnoldii Produces enormous flowers that can produce up to 4 million seeds Figure 38.1 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Concept 38.1: Pollination enables gametes to come together within a flower In angiosperms, the dominant sporophyte Produces spores that develop within flowers into male gametophytes (pollen grains) Produces female gametophytes (embryo sacs) Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of angiosperm reproduction Anther Stamen Stigma Carpel

Germinated pollen grain (n) (male gametophyte) on stigma of carpel Anther at tip of stamen Style Filament Ovary (base of carpel) Ovary Pollen tube Ovule Embryo sac (n)

(female gametophyte) Sepal Egg (n) FERTILIZATION Petal Receptacle Sperm (n) Mature sporophyte Seed plant (2n) with (develops flowers from ovule) (a) An idealized flower.

Key Zygote (2n) Seed Haploid (n) Diploid (2n) (b) Simplified angiosperm life cycle. See Figure 30.10 for a more detailed version of the life cycle, including meiosis. Figure 38.2a, b Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Germinating seed Embryo (2n) (sporophyte) Simple fruit (develops from ovary) Flower Structure Flowers Are the reproductive shoots of the angiosperm sporophyte Are composed of four floral organs: sepals, petals, stamens, and carpels Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Many variations in floral structure Have evolved during the 140 million years of angiosperm history SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION Lupine inflorescence Bilateral symmetry (orchid) Superior ovary Sunflower inflorescence Sepal

Semi-inferior ovary Inferior ovary Radial symmetry (daffodil) Fused petals REPRODUCTIVE VARIATIONS Figure 38.3 Maize, a monoecious species Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dioecious Sagittaria latifolia (common arrowhead)

Gametophyte Development and Pollination In angiosperms Pollination is the transfer of pollen from an anther to a stigma If pollination is successful, a pollen grain produces a structure called a pollen tube, which grows down into the ovary and discharges sperm near the embryo sac Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pollen Develops from microspores within the sporangia of anthers Pollen sac (microsporangium)

(a) Development of a male gametophyte (pollen grain) 1 Each one of the microsporangia contains diploid microsporocytes (microspore mother cells). Microsporocyte MEIOSIS Microspores (4) 2 Each microsporocyte divides by meiosis to produce

four haploid microspores, each of which develops into a pollen grain. Figure 38.4a 3 A pollen grain becomes a mature male gametophyte when its generative nucleus divides and forms two sperm. This usually occurs after a pollen grain lands on the stigma of a carpel and the pollen tube begins to grow. (See Figure 38.2b.)

Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Each of 4 microspores Generative cell (will form 2 sperm) MITOSIS Male Gametophyte (pollen grain) Nucleus of tube cell 20 m

75 m Ragweed pollen grain KEY to labels Haploid (2n) Diploid (2n) Embryo sacs Develop from megaspores within ovules (b) Development of a female gametophyte (embryo sac)

Megasporangium Ovule MEIOSIS Megasporocyte Integuments Micropyle Surviving megaspore Female gametophyte (embryo sac) MITOSIS Ovule Antipodel Cells (3)

Polar Nuclei (2) Egg (1) Integuments Haploid (2n) Diploid (2n) 100 m Key to labels Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Synergids (2)

1 Within the ovules megasporangium is a large diploid cell called the megasporocyte (megaspore mother cell). 2 The megasporocyte divides by meiosis and gives rise to four haploid cells, but in most species only one of these survives as the megaspore. 3 Three mitotic divisions of the megaspore form the embryo sac, a

multicellular female gametophyte. The ovule now consists of the embryo sac along with the surrounding integuments (protective tissue). Embryo sac Figure 38.4b Mechanisms That Prevent Self-Fertilization Many angiosperms Have mechanisms that make it difficult or impossible for a flower to fertilize itself Stigma

Stigma Anther with pollen Pin flower Thrum flower Figure 38.5 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings The most common anti-selfing mechanism in flowering plants Is known as self-incompatibility, the ability of a plant to reject its own pollen

Researchers are unraveling the molecular mechanisms that are involved in selfincompatibility Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some plants Reject pollen that has an S-gene matching an allele in the stigma cells Recognition of self pollen Triggers a signal transduction pathway leading to a block in growth of a pollen tube Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 38.2: After fertilization, ovules develop into seeds and ovaries into fruits

Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Double Fertilization After landing on a receptive stigma A pollen grain germinates and produces a pollen tube that extends down between the cells of the style toward the ovary The pollen tube Then discharges two sperm into the embryo sac Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings In double fertilization One sperm fertilizes the egg The other sperm combines with the polar

nuclei, giving rise to the food-storing endosperm Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Growth of the pollen tube and double fertilization Pollen grain Stigma Pollen tube 1 If a pollen grain germinates, a pollen tube grows down the style toward the ovary. Polar nuclei

Egg 2 sperm Style Ovary Ovule (containing female gametophyte, or embryo sac) Micropyle 2 The pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule. 3 One sperm fertilizes the egg, forming the zygote.

The other sperm combines with the two polar nuclei of the embryo sacs large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ovule Polar nuclei Egg Two sperm about to be discharged Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n)

(egg plus sperm) Figure 38.6 From Ovule to Seed After double fertilization Each ovule develops into a seed The ovary develops into a fruit enclosing the seed(s) Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosperm Development Endosperm development Usually precedes embryo development In most monocots and some eudicots The endosperm stores nutrients that can be

used by the seedling after germination In other eudicots The food reserves of the endosperm are completely exported to the cotyledons Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Embryo Development The first mitotic division of the zygote is transverse Splitting the fertilized egg into a basal cell and a terminal cell Ovule Endosperm nucleus Integuments Zygote Zygote

Terminal cell Basal cell Proembryo Suspensor Basal cell Figure 38.7 Cotyledons Shoot apex Root apex Suspensor Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Seed coat Endosperm Structure of the Mature Seed The embryo and its food supply Are enclosed by a hard, protective seed coat Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a common garden bean, a eudicot The embryo consists of the hypocotyl, radicle, and thick cotyledons Seed coat Epicotyl Hypocotyl

Radicle Cotyledons (a) Common garden bean, a eudicot with thick cotyledons. The fleshy cotyledons store food absorbed from the endosperm before the seed germinates. Figure 38.8a Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings The seeds of other eudicots, such as castor beans Have similar structures, but thin cotyledons Seed coat Endosperm Cotyledons

Epicotyl Hypocotyl Hypocotyl Radicle Radicle (b) Castor bean, a eudicot with thin cotyledons. The narrow, membranous cotyledons (shown in edge and flat views) absorb food from the endosperm when the seed germinates. Figure 38.8b Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings The embryo of a monocot Has a single cotyledon, a coleoptile, and a coleorhiza Pericarp fused with seed coat

Scutellum (cotyledon) Coleoptile Coleorhiza (c) Maize, a monocot. Like all monocots, maize has only one cotyledon. Maize and other grasses have a large cotyledon called a scutellum. The rudimentary shoot is sheathed in a structure called the coleoptile, and the coleorhiza covers the young root. Figure 38.8c Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosperm Epicotyl Hypocotyl

Radicle From Ovary to Fruit A fruit Develops from the ovary Protects the enclosed seeds Aids in the dispersal of seeds by wind or animals Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fruits are classified into several types Depending on their developmental origin Carpels Flower Ovary

Stigma Stamen Stamen Ovule Raspberry flower Pea flower Carpel (fruitlet) Seed Stigma Ovary Stamen

Pea fruit (a) Simple fruit. A simple fruit develops from a single carpel (or several fused carpels) of one flower (examples: pea, lemon, peanut). Raspberry fruit (b) Aggregate fruit. An aggregate fruit develops from many separate carpels of one flower (examples: raspberry, blackberry, strawberry). Figure 38.9ac Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pineapple inflorescence Each segment

develops from the carpel of one flower Pineapple fruit (c) Multiple fruit. A multiple fruit develops from many carpels of many flowers (examples: pineapple, fig). Seed Germination As a seed matures It dehydrates and enters a phase referred to as dormancy Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Seed Dormancy: Adaptation for Tough Times 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 cues Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings From Seed to Seedling Germination of seeds depends on the physical process called imbibition The uptake of water due to low water potential of the dry seed

Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings The radicle Is the first organ to emerge from the germinating seed In many eudicots A hook forms in the hypocotyl, and growth pushes the hook above ground Foliage leaves Cotyledon Epicotyl Hypocotyl Cotyledon Hypocotyl

Cotyledon Hypocotyl Radicle (a) Figure 38.10a Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Seed coat Common garden bean. In common garden beans, straightening of a hook in the hypocotyl pulls the cotyledons from the soil. Monocots Use a different method for breaking ground when they germinate

The coleoptile Pushes upward through the soil and into the air Foliage leaves Coleoptile Figure 38.10b Coleoptile Radicle (b) Maize. In maize and other grasses, the shoot grows straight up through the tube of the coleoptile. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 38.3: Many flowering plants clone

themselves by asexual reproduction Many angiosperm species Reproduce both asexually and sexually Sexual reproduction Generates the genetic variation that makes evolutionary adaptation possible Asexual reproduction in plants Is called vegetative reproduction Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mechanisms of Asexual Reproduction Fragmentation Is the separation of a parent plant into parts that develop into whole plants Is one of the most common modes of asexual reproduction

Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings In some species The root system of a single parent gives rise to many adventitious shoots that become separate shoot systems Figure 38.11 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vegetative Propagation and Agriculture Humans have devised various methods for asexual propagation of angiosperms Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Clones from Cuttings

Many kinds of plants Are asexually reproduced from plant fragments called cuttings Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Grafting In a modification of vegetative reproduction from cuttings A twig or bud from one plant can be grafted onto a plant of a closely related species or a different variety of the same species Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Test-Tube Cloning and Related Techniques Plant biologists have adopted in vitro methods To create and clone novel plant varieties

(a) Just a few parenchyma cells from a carrot gave rise to this callus, a mass of undifferentiated cells. Figure 38.12a, b Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) The callus differentiates into an entire plant, with leaves, stems, and roots. In a process called protoplast fusion Researchers fuse protoplasts, plant cells with their cell walls removed, to create hybrid plants Figure 38.13 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

50 m Concept 38.4: Plant biotechnology is transforming agriculture Plant biotechnology has two meanings It refers to innovations in the use of plants to make products of use to humans It refers to the use of genetically modified (GM) organisms in agriculture and industry Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Artificial Selection Humans have intervened In the reproduction and genetic makeup of plants for thousands of years Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Maize Is a product of artificial selection by humans Is a staple in many developing countries, but is a poor source of protein Figure 38.14 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Interspecific hybridization of plants Is common in nature and has been used by breeders, ancient and modern, to introduce new genes Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reducing World Hunger and Malnutrition Genetically modified plants

Have the potential of increasing the quality and quantity of food worldwide Genetically modified rice Ordinary rice Figure 38.15 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 38.16 The Debate over Plant Biotechnology There are some biologists, particularly ecologists Who are concerned about the unknown risks associated with the release of GM organisms (GMOs) into the environment

Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Issues of Human Health One concern is that genetic engineering May transfer allergens from a gene source to a plant used for food Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Possible Effects on Nontarget Organisms Many ecologists are concerned that the growing of GM crops Might have unforeseen effects on nontarget organisms Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Addressing the Problem of Transgene Escape

Perhaps the most serious concern that some scientists raise about GM crops Is the possibility of the introduced genes escaping from a transgenic crop into related weeds through crop-to-weed hybridization Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Despite all the issues associated with GM crops The benefits should be considered Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

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