Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Chapter 38,Angiosperm Reproduction and Biotechnology,Review,In angiosperms,the dominant sporophyte,(remember that,alternation of generations,as a key plant trait),Produces male gametophytes(pollen grains)within anthers,Produces female gametophytes(embryo sacs)within the ovule,With fertilization,(union of sperm and egg),the ovules develop into seeds,while the ovary becomes the fruit.,An overview of angiosperm reproduction,Anther at,tip of stamen,Filament,Anther,Stamen,Pollen tube,Germinated pollen grain,(,n,)(male gametophyte),on stigma of carpel,Ovary(base of carpel),Ovule,Embryo sac(,n,),(female gametophyte),FERTILIZATION,Egg(,n,),Sperm(,n,),Petal,Receptacle,Sepal,Style,Ovary,Key,Haploid(,n,),Diploid(2,n,),An idealized flower.,angiosperm life cycle.,Mature sporophyte,plant(,2n,)with,flowers,Seed,(,develops,from ovule,),Zygote,(2,n,),Embryo(2,n,),(sporophyte),Simple fruit,(,develops from ovary,),Germinating,seed,Seed,Carpel,Stigma,Flower Structure,Flowers,Are the reproductive shoots of the angiosperm sporophyte,Are composed of four floral organs:sepals,petals,stamens,and carpels,Many variations in floral structure have evolved,Bilateral symmetry,(orchid),Sepal,Radial symmetry,(daffodil),Fused petals,Semi-inferior ovary,Inferior ovary,Superior,ovary,Lupine inflorescence,Sunflower inflorescence,Maize,a monoecious,species,Dioecious,Sagittaria,latifolia,(common,arrowhead),REPRODUCTIVE VARIATIONS,SYMMETRY,OVARY LOCATION,FLORAL DISTRIBUTION,Flower variations,(Inflorescences,are clusters of small flowers),(Stamate and carpellate flowers on the same plant),(Stamate and carpellate flowers on separate plants.Reduces inbreeding),(Ovary relation to stamen,petal,and sepal attachment site),Flower Parts,Sepals,-enclose and protect flower bud before it opens,Petals,may be colored to advertise the flower to pollinators,Carpels,ovary,base,slender neck(,style,),and,stigma,(a landing platform for pollen),Stamen,filament,stalk and terminal,anther,(which contains the pollen sacs),Complete flowers,have all four basic flower organs,Incomplete,flowers,lack something(grass flower may lack petals),Pollination,Pollination is the transfer of pollen from an anther to a stigma,If pollination is successful,a pollen grain produces a,pollen tube,which grows down into the ovary and discharges sperm near the embryo sac,Pollen grain development,Pollen d,evelops from microspores within the sporangia of anthers,A,pollen grain,becomes a,mature male gametophyte,when its 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.),Each,microsporo-,cyte,divides by,meiosis to produce,four haploid,microspores,each of which,develops into,a pollen grain.,Pollen sac,(microsporangium),Micro-,sporocyte,Micro-,spores(4),Each of 4,microspores,Generative,cell(will,form 2,sperm),Male,Gametophyte,(pollen grain),Nucleus,of tube cell,Each one of the,microsporangia,contains diploid,microsporocytes,(microspore,mother cells).,75,m,20,m,Ragweedpollengrain,MEIOSIS,MITOSIS,KEYto labels,Haploid(,2n,),Diploid(,2n,),Microsporangium,Microsporocyte,Microspore,Pollen grain,Key,to labels,MITOSIS,MEIOSIS,Ovule,Ovule,Integuments,Embryo,sac,Mega-,sporangium,Mega-,sporocyte,Integuments,Micropyle,Surviving,megaspore,Antipodel,Cells(3),Polar,Nuclei(2),Egg(1),Synergids(2),Within the ovules,megasporangium,is a large diploid,cell called the,megasporocyte,(megaspore,mother cell).,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).,Female gametophyte,(embryo sac),Diploid(,2n,),Haploid(,2n,),100,m,The megasporocyte divides by,meiosis and gives rise to four,haploid cells,but in most,species only one of these,survives as the,megaspore,.,Embryo sac development,Embryo sacs develop from megaspores within ovules,Megasporangium,Megasporocyte,Megaspore,Embryo sac,Mechanisms That Prevent Self-Fertilization,The most common anti-selfing mechanism in flowering plants is known as,self-incompatibility,the ability of a plant to reject its own pollen,Some angiosperms have structural adaptations that make it difficult for a flower to fertilize itself,Stigma,Anther,with,pollen,Stigma,Pin flower,Thrum flower,Some species produce two types of flowers:,Pin flowers-long styles/short stamens,Thrum flowers-short styles/long stamens,Pollinating insects would collect pollen on different body areas and deposit the pollen on the opposite flower type!,Detaselling corn,In corn,hybrid seed corn is far superior to inbred(self-fertilized corn),Detaselling involves removing the pollen-producing top part of the plant,the tassel,so the corn cant pollin