Reproduction in Plants

Name: __________________ Topic: Reproduction in Plants LO:Defineasexualreproductionastheprocessresultingintheproductionofgenetically identical offspring from one parent The process resulting in the production ofgeneticallyidenticaloffspring fromoneparent, without the fusion of nuclei of haploid gametes. (E.g. through mitosis / binaryfission) LO:Definesexualreproductionastheprocessinvolvingthefusionofnucleitoform a zygote and the production of genetically dissimilar offspringTheprocessinvolvingthefusionofnucleiofthehaploidfemalegameteandthehaploidmalegameteto forma diploidzygoteandtheproductionof geneticallydissimilaroffspring. Differences between asexual reproduction and sexual reproduction: Asexual Reproduction Sexual Reproduction Doesnotinvolvefusionofnucleiofgametes Involves thefusionof ahaploidnucleusofmale gametewith ahaploid nucleusoffemale gametetoform adiploidzygote Onlyoneparent required Requirestwoparents (except forplants with bisexual flowers) Offspring aregeneticallyidentical Offspring aregeneticallydifferent Relativelyquickermethod Slowermethod Concepts Summary NotesNan Hua High School Biology 1

Name: __________________ Topic: Reproduction in Plants LO:Identifyanddraw, usingahandlensifnecessary, thesepals,petals,stamensandcarpelsof one,locallyavailable,named,insect-pollinated,dicotyledonousflower, and examine the pollen grains using a microscope Concepts Summary NotesNan Hua High School Biology 2

Name: __________________ Topic: Reproduction in Plants LO: State the functions of the sepals, petals, anthers and carpelsSepals Modified leaves whichenclose and protectthe otherparts of theflower in thebud stage. Petals Brightly coloured and conspicuousmodified leavestoattractinsectsfor pollination and provide aplatformforinsects to land. Stamen Consists ofanther and filament; anther has 2 lobes,eachcontains 2 pollen sacs which producepollen grains.The pollen grain containstwo male gametes. Carpel (pistil)Consists of one or morestigmaswhich capture pollengrains,astyle through which pollen tube grows, and an ovary whichcontains ovules.The ovum is in the ovule. LO:Usea handlenstoidentifyanddescribethestamensandstigmasofone,locallyavailable,named,wind-pollinatedflower, andexaminethepollengrainsusing a microscope Concepts Summary NotesNan Hua High School Biology 3

Name: __________________ Topic: Reproduction in Plants LO:Outlinetheprocessofpollinationanddistinguishbetweenself-pollinationand cross-pollination● Pollination is thetransfer of pollen grains fromthe anther to the stigma. Self-pollination (A and B): Concepts Summary NotesNan Hua High School Biology 4

Name: __________________ Topic: Reproduction in Plants ● The process of pollination whereby the pollen grains from the anther aretransferred to the stigma ofthe same floweror adifferent flower in the sameplant. ● Advantages: ● Disadvantages:1. Offspring produced aregenetically similarto parentscausing fewervarieties of offspring, less adapted to changes in the environment.2. Probability of harmful recessive alleles being expressed in offspring ishigher as compared with cross-pollination.● Ways to prevent self-pollination:1. Stamen and pistil mature at different times2. Unisexual plant (plant producing either male or female flowers)3. Stigma of the flower is above the anther4. Stigma and anther are situated far apart from each other. Cross-Pollination (C):● The process of pollination whereby the pollen grains from the anther aretransferred to the stigma ofanother flower on anotherplant of the same species. ● Advantages Concepts Summary NotesNan Hua High School Biology 5

Name: __________________ Topic: Reproduction in Plants ● Disadvantages:1.Two different plantsof the same species are required.2. Dependent onexternal factorsfor pollination.3. More energy and pollens are wasted. Note:Self-pollination and cross-pollination bothresult in sexual reproduction. LO:Compare,usingfreshspecimens,aninsect-pollinatedandawind-pollinatedflowerInsect pollination● An insect lands on thepetals.● The insect follows thenectar guideinto the flower.● The insect brushes against thestigma.● Pollen grains from another flower,which the insecthad visited earlier aretransferredfrom the insect’s body anddepositedontothestigma.● As the insect brushes the anther,pollen grains willstick to the insect’s back,which will be used to pollinate another flower. Wind pollination● Thependulous filamentsexpose the anthers to thewind.Concepts Summary NotesNan Hua High School Biology 6

Name: __________________ Topic: Reproduction in Plants ● When the wind blows,pollen grainsare released and carried away by the wind.● The pollen grains land onlarge and feathery stigma,whichincreases surfacearea to trap the pollen grains. Feature CharacteristicsInsect-pollinated flowers Wind-pollinated flowers Petals Flowers are usually largeand conspicuous withbrightly-coloured petals. Flowers are usually small anddull-coloured, without petals. Stigmas Stigmas are usuallysmalland compact. Stigmasare large and featherytoprovide alarge surface areato trappollen.Stamens Stamens arenotpendulous. Stamens havelong pendulousfilaments with protruding anthers. Pollen Pollen isfairlyabundantandlarger with rough surfaces. Pollen ismore abundant withsmoothsurfacesand arelight and tiny. Nectar guides Nectar guidesmay bepresent on the petals toguide insects. Nectar guides are absent. LO:Describethegrowthofthepollentubeanditsentryintotheovulefollowedby fertilization(productionof endospermanddetailsof developmentarenotrequired)Sequence of Fertilisation:● After pollination, the pollen grainsgerminateinresponse to asugary fluidsecreted by the mature stigma● Apollen tubegrows out of each pollen grain● Thecytoplasm, thegenerative nucleusandthe pollentube nucleusof eachpollen grain pass into the pollen tube● The growth of pollen tube iscontrolled by the pollentube nucleus, and as itgrows,enzymes are secretedto digest the surroundingtissue of thestigma andthe style, so as to allow the pollen tube topenetratethrough the styleas it grows Concepts Summary NotesNan Hua High School Biology 7

Name: __________________ Topic: Reproduction in Plants ● The pollen tubeenters the ovulethrough an opening called themicropyle● Along the way, thegenerative nucleus divides to formtwo male gametes, andeventually thepollen tube nucleus disintegrates● Within the ovule, the tip of the pollen tubeabsorbssapandburststo release thetwo male gametes● The haploidnucleus of one male gametefuses withthe haploid nucleus of theovumto form the diploidzygote, while thenucleusof the other male gametefuseswith thedefinitive nucleusto form theendospermnucleus.This results indouble fertilisation.● The zygote thendivides mitotically and develops intothe embryo in the seed,while the endosperm nucleus divides to give rise to the food storage tissue calledtheendosperm. Concepts Summary NotesNan Hua High School