4Two types of reproduction AsexualSexualinvolves one parentinvolves no gamete (sex cell)offspring are genetically identical to the parents – mitotic cell divisionusually involves 2 parentsinvolves gametesinvolves fertilizationfusion of the nuclei of male & female gametes zygoteoffspring are genetically different from each of their parents
5Types of asexual reproduction Examples of asexual reproductionBinary fissionBuddingSpore formationFragmentationVegetative propagation
6division of unicellular organisms into equal halves e.g. Amoeba Binary fissionBinary fissiondivision of unicellular organisms into equal halvese.g. Amoeba
7two daughter Amoebae are formed Binary fissionnucleus divides equally into two by mitosisnucleuscytoplasm constrictstwo daughter Amoebae are formed
8production of buds, which grow to new individuals e.g. yeast Buddingproduction of buds, which grow to new individualse.g. yeast
9Buddinga yeast cella nucleus moves into the buda bud is formednucleusvacuolenucleus divides into twoa nucleus remains in the parent cell
10Buddingthe new cell breaks off from the parent cell
11produced in large numbers. occurs in fungi e.g. Mucor, Rhizopus Spore formationproduced in large numbers.occurs in fungie.g. Mucor, Rhizopus
12Fungi are saprophytes- causing rotting of dead organic matters Spore formationFungi are saprophytes- causing rotting of dead organic mattersProduce spores for reproduction and dispersal
16regeneration in flatworm Fragmentationregeneration in flatworm
17Vegetative propagation development of new plants from vegetative / food storage organsoccurs in flowering plantse.g. potato, onion, ginger, Gladiolus
18development of new plants from vegetative / food storage organs 1. Bulb 2. tuber 3. rhizome 4. corm
19Vegetative propagation budstorage organaerial partsWhen conditions become unfavourable such as winter,the aerial parts of the plant die and the storage organ stops growing underground.It survives through bad conditions for growth.
20Vegetative propagation When conditions are suitable for growth,a new plant develops from a bud.The storage organ provides food for the development of the new plant.
21Vegetative propagation Adventitious roots are formed.They absorb water and minerals.The shoot grows up and develops leaves.aerial shootadventitious roots
22Vegetative propagation leafThe storage organ dries up as food is used up for growth.
23Vegetative propagation The plant can now survive on its own by food made from photosynthesis.new storage organSome food made from photosynthesis is passed to a new storage organ.previous storage organ
24Vegetative propagation Examples of storage organsTuberBulbRhizomeCormswollen underground steme.g. potato tubershort underground stem with layers of fleshy ‘scale leaves’e.g. onion bulbhorizontally growing underground steme.g. gingerrhizomeshort swollen underground steme.g. Gladioluscorm
25Vegetative propagation TuberVegetative propagation of a potato plant
26Vegetative propagation TuberVegetative propagation of a potato plantIn springIn winterThe aerial shoots die but the new tubers remain dormant.Each bud can produce a new independent plant.
27tuber formed by last year’s plant shootIn summerold tubernew tubersadventitious rootseye (a bud)The buds use the food stored in the tuber to produce adventitious roots and shoots.Excess food made in the leaves is sent to the underground shoots and stored.
28Vegetative propagation TuberVegetative propagation of a potato plant
30Vegetative propagation BulbGrowth of an onion bulbscale leaffleshy leafbudstemrootThe bud remains dormant.
31After dormancy, the bud develops. new flower stalkleaffleshy leafnew bulbAfter dormancy, the bud develops.The leaves make and provide food for the growth of a new bud.The fleshy leaves provide food for the development of the shoot.They become dry scale leaves after their food storage has been used up.
32Vegetative propagation RhizomeGrowth of a ginger rhizome
33Vegetative propagation Growth of a ginger rhizomeRhizomeThe food produced from photosynthesis passes downwards to the underground parts.
34Vegetative propagation Growth of a ginger rhizomeRhizomelateral bud grows into daughter rhizomeThe food produced from photosynthesis passes downwards to the underground parts.Food passes upwards from the older parts to the growing regions.
36Vegetative propagation CormGrowth of a Gladiolus cormIn springbudscale leafremains of last year’s cormFood stored in the swollen stem is passed upwards to the bud for its growth.
37A new corm is developed over the old one each year. aerial shootleafnew cormnew cormold cormWhen the leaves are well developed, the food they made is passed down to the new corm.A new corm is developed over the old one each year.
42Importance of Vegetative Propagation It is the only means of reproduction for seedless plants such as pineapples, seedless grapes, oranges, roses, sugarcane, potato, banana, etc.Plants raised through vegetative propagation are genetically similar. It preserves the type of characters that a plant breeder desires to retain.It is very economical and easy method for the multiplication of plants.
43Artificial propagation by grafting Eg. Fruit treesOrnamental plantsBauhinia of HKGrafting is a method of asexual plant propagation where the tissues of one plant are encouraged to fuse with those of another.In most cases, one plant is selected for its roots, and this is called the stock or rootstock. The other plant is selected for its stems, leaves, flowers, or fruits and is called the scion.
44Artificial Vegetative reproduction To ensure a quick growth union, all cut surfaces are covered with a soft wax to prevent drying. The tissues of both the stock and the scion will fuse together and will make organic connection, getting nourishment from the stock, but producing fruits of scion retaining parental characters. Grafting is not possible is monocot plants since cambial activity is essential for the union of stocks and scion.Grafting blends the properties of two plants. It is also used in the production of dwarf fruit trees for the home gardens. High quality roses are usually grafted on wild rose root stocks. Other plants where grafting has been performed successfully are rubber, apple, pear, mango and guava.
45Grafting peach into plum Main grafting steps: Trimming bark after cutting a branch to be graftedNext: Budwood inserted into branchCompleted bark graft which has been tied with tape and waxed with grafting waxThese peach grafts were been successful and have already produced blossomsThis wild plum tree has now become half peach and half plum
46The ‘grafted’ Bauhinia appear in two segments: the upper half is Bauhinia blakeana 洋紫荊 and the lower half is Bauhinia purpurea 紅花羊蹄甲. When you look at the joint carefully, then you will notice that the bark textures on both halves are significantly different. Also, the leaves on the branches and those near the foot vary a little bit. When we see the ‘grafted’ Bauhinia, Bauhinia blakeana is just one of the tree names. Bauhinia purpurea is another one. (Well, if the foot of this tree does have leaves and flowers, then it should be labeled with two names!)
47ADVANTAGES and DISADVANTAGES What are theADVANTAGES and DISADVANTAGESof Artificial Propagation ?
49Advantages Disadvantages Vegetative propagation A relatively quick way to produce new plantsOvercrowding…..Good characters are passed to the offspringDiseases in parents…..Offspring are identical…..No external agents or other plants are neededUndesirable characters….
50Advantages Disadvantages Vegetative propagation A relatively quick way to produce new plantsOvercrowding can occur which causes competition for resourcesDisease of the parent plants can easily be transmitted to the offspringGood characters of the parent are passed to the offspringOffspring have no new features No new features in offspring to adapt to any changes in environmental conditionsNo external factors or other plants are needed for reproductionUndesirable characters are passed on to the offspring
51Importance of Vegetative Propagation It is the only means of reproduction for seedless plants such as pineapples, seedless grapes, oranges, roses, sugarcane, potato, banana, etc.Plants raised through vegetative propagation are genetically similar. It preserves the type of characters that a plant breeder desires to retain.It is very economical and easy method for the multiplication of plants.
55Application of tissue culture Micro propagation of plantsPlant tissue in very small amounts can produce hundreds or thousands of plants continuously. By using tissue culture methods, millions of plants with the same genetic characteristics can be obtained.Improved crop In crop improvement efforts, pure strains can take six to seven generations of self-pollination or crosses. Through tissue culture techniques, homozygous plants can be obtained in a short time by producing haploid plants through pollen culture, anther or ovaries followed by chromosome doubling.Production of disease-free plants (virus) Tissue culture technology has contributed in a plant that is free from viruses. In plants that have been infected with the virus, the cells in the bud tip (meristem) is an area that is not infected with the virus. In this way virus-free plants can be obtained from the meristem.Genetic transformation For example, bacterial gene transfer (such as cry genes from Bacillus thuringiensis) into the plant cells )
5620.3 Sexual reproduction in flowering plants flowering plants reproduce sexually by producing flowersantherstamenstigmafilamentstylecarpelpetalovaryovulenectaryreceptaclesepalsepals, petals, stamens and carpels are attached to thisflower stalkStructure of a flower
57Structure of a flower Sepals make up the outermost ring (calyx) of a flowerprotect the inner parts of the flower when it is a bud
58make up the second ring (corolla) of a flower petalPetalsmake up the second ring (corolla) of a flowermay be brightly-coloured to attract insectsnectaries may be present at the base to produce nectar which attracts insectsmay have insect guides to lead insects towards the nectariesinsect guide
59male reproductive organs Stamensmale reproductive organsconsists of 2-4 pollen sacs inside which pollen grains are formedfilamentanthersupports antherpollen sacs split open to release pollens which contain male gametesantherwhen anthers ripenpollen sacsfilament
60female reproductive parts Carpelsstigmastylethe centre of a flowerfemale reproductive partseach consists ofstigma (receives pollen grains)style (carries the stigma)ovary (with ovules inside)
61ovules are protected by integument which has a small hole (micropyle) Carpelsstigmaovules are protected by integument which has a small hole (micropyle)styleovary wallintegumentsovules contain the female gametesfemale gameteovuleovaryeach ovule is attached to the ovary wall by a stalkmicropyleStructure of a carpel
62Pollination the transfer of pollen grains from anthers to stigmas fertilization of male & female gametes in ovulescross-pollinationself-pollination1Pollination2wind-pollinationinsect-pollination
63Cross-pollination and self-pollination pollen grains are transferred to a different plant
64Cross-pollination and self-pollination pollen grains are transferred within the same plant
65Inbreeding (Self-pollination) Advantages:Preserves well-adapted genotypesInsures seed set in the absence of pollinatorsDisadvantages:Decreases genetic variability
66Outbreeding (Cross-pollination) Advantages:Increases genetic variabilityStrong evolutionary potentialAdaptation to changing conditionsSuccessful in long-termDisadvantages:Can destroy well-adapted genotypes (offspring are not guaranteed to be viable)Relies on effective cross-pollination
67Wind-pollination and insect-pollination pollinated by windInsect pollinationpollinated by insectsThe flowers are structurally adapted to pollination.Wind-pollinated flowersInsect-pollinated flowers
68Structural adaptation of wind-pollinated flowers scentnectariespollen grainlarge numbersmooth and drylight in weight
69Structural adaptation of wind-pollinated flowers scentnectariesstigmalargefeatheryprojects outside the flower for picking up pollen grains from air
70Structural adaptation of wind-pollinated flowers scentpetalnectariessmallgreen or dull-colouredpollen grainstigma
71Structural adaptation of wind-pollinated flowers scentpetalnectariespollen grainantherstigmahangs outside the flower, exposed to windloosely attached to filament so that light wind can shake it
72pollen grains of this flower stick onto the leg of the bee Structural adaptation of insect-pollinated flowersscentpollen grains of this flower stick onto the leg of the beenectariespollen grainsmaller numberrough and sticky/with hooksheavier
73Structural adaptation of insect-pollinated flowers stigmascentsmallerstickyremains inside the flowernectariespollen grain
74Structural adaptation of insect-pollinated flowers stigmascentnectariespollen grainpetallargerbrightly-coloured
75Structural adaptation of insect-pollinated flowers stigmascentnectariesantherinside the flower where insects will brush against itfirmly attached to prevent from being torn away by insectspollen grainpetal
76Outbreeder or Inbreeder? Often one can tell just by looking at a flower whether it cross-pollinates or self-pollinates.OUTBREEDERINBREEDERself-incompatibilitySize of flowerscolorsnectariesscentnectar guidesanthers positionNumber of pollen grainsstyle position
77Outbreeder or Inbreeder? Often one can tell just by looking at a flower whether it cross-pollinates or self-pollinates.OUTBREEDERINBREEDERself-incompatibleself-compatiblelarge flowerssmall flowersbright colorsmono-colorednectaries presentnectaries absentscented flowersunscented flowersnectar guides presentnectar guides absentanthers far from stigmaanthers close to stigmamany pollen grainsfewer pollen grainsstyle not included in flowerstyle included in flower
78The growth of pollen tube and fertilization Pollen grains land on the stigma of the same species.styleflower stalksepalThe growth of pollen tube and fertilization
79The growth of pollen tube and fertilization Sugary solution at the tip of the stigma stimulates the pollen grain to develop a pollen tube.styleflower stalksepalThe growth of pollen tube and fertilization
80The growth of pollen tube and fertilization Pollen tube grows down the styleand eventually into the ovary by secreting enzymes to digest tissues of the style.The male gamete moves towards the ovule.stylemale gameteflower stalksepalThe growth of pollen tube and fertilization
81The growth of pollen tube and fertilization After growing into the ovary, the tube grows through the micropyle of the ovule andthe tip of the tube bursts to release the male gamete into the ovule.styleovulemale gameteovaryflower stalksepalmicropyleThe growth of pollen tube and fertilization
82The growth of pollen tube and fertilization The male gamete enters the ovule and fuses with the female gamete to form a zygote.styleovulemale gameteovaryflower stalksepalmicropyleThe growth of pollen tube and fertilization
8320.4 What happens to the floral parts after fertilization? wither and drop offremains of stigma and stylescarstamensepalintegumentseed coatpetalovary wallfruit wallovuleseedovumembryoA Bauhinia flower after fertilizationFruit(pod) splits open to two halves
84undeveloped plant embryo Fruits and seedsFruitconsists ofprotectshelpsfruit wallseedplant dispersalmade up ofseed coatprotectsundeveloped plant embryoprovides foodfood store
85Fruits and seeds Structure of a mung bean seed micropyle hilum a hole through which embryo absorbs water before it germinateshilumseed coata scar on the surface of the coat;surrounds the embryo and protects it from damageformed when the ovule detaches from the ovary walland against attack of micro-organisms such as bacteria and fungiExternal appearance
86Structure of a mung bean seed plumuledevelops into the shootradicleembryodevelops into the rootcotyledonsact as food storescontain starch and proteins to supply food for the plumule and radicle to developEmbryo cut opened
87To reduce overcrowding and competition for materials. Dispersal of seeds and fruitsWhy seeds and fruitshave to be dispersed todistances far awayfrom parents ?To colonize new areas which are suitable for seed germination and survival of species.To reduce overcrowding and competition for materials.
88adaptive features of fruits and seeds are Dispersalwind dispersalanimal dispersaladaptive features of fruits and seeds aresmalllightmay have wings/feathery hairbrightly-colouredsweet, juicy and good to eatmay have hooks
89Concept diagram Reproduction asexual reproduction sexual reproduction can beasexual reproductionsexual reproduction
90vegetative propagation Concept diagramasexual reproductioncan be bybinary fissionbuddingvegetative propagationspore formationby the formation ofartificially achieved bystem tuberbulbrhizomecormcutting
91Concept diagram sexual reproduction flower male gamete female gamete in flowering plantsin mammalsformsbyinvolvesfloweraftermale gametefemale gametepollinationfusion is calledandforfertilizationfertilizationcopulation or IVF