Mills AP Bio 2003/2013 Chapter 27 Reproduction in Flowering Plants Topics: 27.1 Sexual Reproductive...

Mills AP Bio 2003/2013

Chapter 27Reproduction in Flowering

Plants

Topics:27.1 Sexual Reproductive Strategies27.2 Seed Development27.3 Fruits and Seeds27.4 Asexual Reproductive Strategies

Read Textbook Ch 27 and pages 569-572Read Cliffs AP Book

http://samson.kean.edu/~breid/flower_lab/glad1.jpg


Chapter 27 Reproduction in Plants27.1 Sexual Reproductive Strategies

• Life Cycle of flowering Plant– Alternation of generations

• Sporophyte (2n) – Dominant in flowering

plants – plant we recognize

– Diploid – produces haploid spore by meiosis

• Gametophyte (n)– Haploid- produces

diploid zygote– Small and not

independently living (is independent in mosses and ferns)

– (Dominant in mosses)

– Flowering plants’ sperm do not require water to fertilize egg – mosses and ferns do

Memory device:meggagametophyte



• Flower parts– “Female”-ovary and egg

• Pistil (some texts call a carpel)

– Stigma– Style– Ovary (with ovules)

– “Male” – produces pollen grain

• staMEN– Anther (MANther)– filaMENt

– Petals– Sepals




Pistils SEM

http://www.ulb.ac.be/sciences/biodic/ImDicot.html







• Wild peoni– Many stamen and 3 pistils







• Three carpels fused to form a compound pistil– When pistil contains only one carpel, then pistil

and carpel are synonymous




• A single pistil consisting of several fused carpels (A) and several pistils each consisting of a single carpel (B)

http://www.botany.uwc.ac.za/ecotree/flowers/flowerparts2.htm

Carpel is ovule bearing unit. Ovary may have one or more carpels.


http://www.botany.uwc.ac.za/ecotree/flowers/flowerparts2.htm



• Sporophyte (flower) produces haploid spores (microspore and megaspore) by meiosis

• Microspore produces microgametophyte (pollen grains “male”) and megaspore produces megagametophtye (eggs “female”) by mitosis. (sometimes also called macrogametophyte)

• When pollen and egg come together – fertilization – diploid zygote is formed-plant returns to sporophyte stage





• Megaspore (female embryo sac) development

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Angiosperm.html

Functional megaspore divides by mitosis to become:

One egg cellTwo synergid cellsOne central cell with two polar nucleiThree antipodal cells

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Angiosperm.html



Synergid cells – guide pollen tube

Polar nuclei – become endosperm once fertilized

Ovum – egg sporophyte

Antipodal nuclei- no known function – degenerate eventually




• Microspore development (male pollen)

http://www.ualr.edu/~botany/pollendev.gif



Pollen grain formation







Pollen Sac (in anther) SEM





Allergenic Pollen (SEM x1,000). This image is copyright Dennis Kunkel at www.DennisKunkel.com,

http://www.denniskunkel.com/



• Pollination and Fertilization– Pollen usually wind blown (in flowering plants)– Pollen sticks on sticky stigma– Pollen grain contains one generative cell and one tube cell (each haploid)– Generative cell divides by mitosis to produce two sperm cells– Tube cell forms a tube that grows down to the megagametophyte

(embryo sac)– One sperm joins with egg to form zygote– Other sperm joins with both polar nuclei to form triploid endosperm– This double fertilization is unique to flowering plants

Zygote becomes sporophyte embryo

Ovule matures into seed and seed coat

Ovary becomes the fruit

Fertilization animation..\..\Biology\Biology Clipart Movies Animations Sounds\Biology animations\PlantFertilization.mov



Fertilization


From: http://www.emunix.emich.edu/~ghannan/systbot/NewFiles/animation%203801.swf



• Pollination– Animals, wind






Chapter 27 Reproduction in Plants27.2 Seed Development



• Embryo Development – (seed development animation)– Endosperm nucleus divides to become endosperm tissue– Zygote divides into embryo (which will develop cotyledons) and

suspender which will transfer nutrients to the embryo




• Cotyledons– Monocot

• Has one• Doesn’t store food

just passes it from the endosperm to the embryo

– Dicot• Has two• Store nutrients to

feed embryo

• Epicotyl– Area between

cotyledon(s) and first leaves

• Hypocotyl– Below cotyledon(s) –

stem development• Radicle

– Contributes to root development






Embryo Development



• Fruits and Seeds– Seeds

• embryo plus endosperm plus surrounding ovule (seed coat)

– Fruit • Ovary and sometimes

surrounding floral parts• Fruit=mature ovary that

usually contains seeds.

– Many types and varieties of fruits

• Simple (derived from one ovary-simple or compound)– apples peaches

• Compound (develop from several individual ovaries) – blackberry, strawberry

• Grains (corn, wheat,rice, beans, nuts etc.) are dry fruits

– Fruit animation– Good fruit type site:

http://www.botany.uwc.ac.za/ecotree/fruit/fruittypeswin.htm

Chapter 27 Reproduction in Plants27.3 Fruit Types and Seed Dispersal







www.caosclub.org/ members/plan22.html



• Seed dispersal– Many varied ingenious

mechanisms• Explosive• Wind• Water• Animals




• Seed germination– Needs sufficient water, warmth and oxygen– Needs correct chemical regulators– Some need mechanical actions (washing, bacteria, fire)– Some need period of dormancy– All work together to have seed germinate when it is most

likely to survive. Dicot- –if hypocotyl bends – cotyledons come above ground.

Dicot- –if epicotyl bends – cotyledons stay below ground.







• Germination in monocots and dicots– Embryo breaks out of seed coat– Epicotyle bears young leaves called plumule– Monocot tip protcted by coleoptile – dicot bends– Phytochromes (ch 38) stimulate leaf growth









Germination movies:

Corn..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Germination corn.mov

Sunflower..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Germination sunflower.mov

Photomorphism in sunflowers:Sunflowers in light..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Germinating sunflower dark.mov

Sunflowers in dark

..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Germinating sunflower light.mov




• Vegetative propagation– Can occur naturally– Can be “human

induced”• Tissue culture• Capitalize on fact that

plant cells are totipotent

– This is possible because plants contain non differentiated meristematic tissue

Chapter 27 Reproduction in Plants27.4 Asexual Reproduction Strategies


Tissue Culture Animation




• Genetic engineering in plants– Previously,

hybridization, the crossing of different varieties or species of plants, was used to produce plants with desirable traits.

– Now can just ‘insert the gene”

– Can produce plants with• Resistance to disease

and herbicides• More nutritious• Ability to make human

hormones, clotting factors and antibodies

– The sky is the limit, but some advise great caution

Chapter 27 Reproduction in Plants27.4 Asexual Reproduction Strategies


Transgenic Plants



Transgenic Plants- Gene Gun




Evolutionary Overview

• algae mosses ferns gymnosperms angiosperms– Ferns are over 360 million years old – were around way before

the dinosaur (about 220mya)

• avascular seedless (mosses, liverworts, hornworts- which are all bryophytes) vascular seedless (ferns) vascular with seeds (gymnosperms and angiosperms)

• gymnosperms (pine trees etc) with naked seeds angiosperms (flowering plants) with seeds inside ovaries

• Mosses and ferns need water (externally) for fertilization, seeded plants don’t

• Gametophyte (haploid) generation dominant in mosses.• Sporophyte generation dominant in vascular plants (ferns,

angosperms and gymnosperms).



Chapter 27 Reproduction in Plants

• In ferns and mosses, the sporophyte and gametophyte generations are represented by two greatly different plants.

– Among mosses, a sporophyte consists of a long, rigid stalk with a spore-producing container at the end, extending from the top of a soft, leafy, green gametophyte. The sporophyte depends on the gametophyte for food and water. When we think of the green carpet of mosses, it is the gametophyte we are seeing.

– The ferns sporophytes have leaves which are much larger than the gametophytes. They have clusters of sporangia, where the spores develop, called sori form on the edges or underside of each leaf.

– After the spores ripen, they fall to the ground and grow into gametophytes. A fern gametophyte produces both male and female sex cells, and if enough moisture is present, a sperm cell swims to an egg cell and unites with it.

– Once fertilized, the egg grows into an adult sporophyte.

• From: http://www.ecoworld.com/plants/EcoWorld_Plants_Home5.cfm


Gymnosperm Life Cycle


Link to animation: http://bcs.whfreeman.com/thelifewire/content/chp30/30020.html


Gymnosperm Life Cycle Animation




Chapter 27 Reproduction in Plants

Gametophyte (bottom) vs Sporophyte (top) in various “plants”



Mosses (bryophytes)avascular seedless

• http://www.esu.edu/~milewski/intro_biol_two/lab_2_moss_ferns/MossandFern_Diversity.html

In mosses, the sporophyte is small and at least partially erect, with very little specialization of cells and tissues, specifically, no true leaves, stems, or roots. The moss gametophyte has a shoot portion that appears leafy, and has rhizoids which emerge from its base to attach it to the substratum upon which it grows.



Mossesavascular seedless

Gametophyte (haploid)

Sporophyte (diploid)



Mossesavascular seedless



Moss Life Cycle


Life cycle of a Moss Animation




The ferns sporophytes , which are much larger than the gametophyte, have clusters of sporangia (inside sori), on their leaves, where the haploid spores develop. After the spores ripen, they fall to the ground and grow into heart shaped gametophytes.

A fern gametophyte produces both male and female sex cells, and if enough moisture is present, a sperm cell swims to an egg cell and unites with it. Once fertilized, the egg grows into an adult sporophyte

Ferns



Fernsvascular seedless

Sporangia (in sori) on underside of fern leaf









Heart shaped haploid gametophyte

Gametophyte with new sporophyte growing

Fern Life Cycle animation

..\..\Biology\Biology Clipart Movies Animations Sounds\Biology animations\FernLifeCycle[1].mov

http://flightline.highline.edu/jbetzzall/BI100/animations/fern_life_cycle_v2.html


Fern Life Cycle Animation





Gametophyte (haploid)








The End










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Mills AP Bio 2003/2013 Chapter 27 Reproduction in Flowering Plants Topics: 27.1 Sexual Reproductive...

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