Reproduction in Plants (Part I, II & III) PDF

17/7/2024 BL2131 Foundation in Biology II Part I (Intro & Flower Parts) Topic 5: Reproduction in flowering plants 1 1 Recap from T4 Heredity From asexual and sexual reproduction, you should b...

17/7/2024 BL2131 Foundation in Biology II Part I (Intro & Flower Parts) Topic 5: Reproduction in flowering plants 1 1 Recap from T4 Heredity From asexual and sexual reproduction, you should be able to: 1. define ‘asexual reproduction’ as the process resulting in the production of genetically identical offspring from one parent; 2. define ‘sexual reproduction’ as the process involving the fusion of two nuclei to form a zygote, resulting in the production of genetically dissimilar offspring. 2 1  17/7/2024 T5 Reproduction In Plants Focus on parts of flower & their functions. You should be able to: identify and draw the sepals, petals, stamens and carpels of a flower; (in practical) state the functions of the sepals, petals, stamens and carpels; 3 T5 Reproduction In Plants Parts of a typical flower Flowers may occur singly or in clusters, called inflorescences. stigma petal style anther carpel stamen ovary filament ovule sepal receptacle pedicel 4 2  17/7/2024 T5 Reproduction In Plants Parts of a typical flower Sepal (Collective: calyx) The sepal is a modified leaf that protects the flower in the bud stage. All the sepals together make up the calyx. Some flowers have another layer of floral leaves outside the sepals sepal known as the epicalyx. 5 T5 Reproduction In Plants Parts of a typical flower Petal (Collective: corolla) Petal The petal is a modified leaf that forms the most obvious part of a flower. In insect-pollinated flowers, the petal is – brightly coloured to attract insects for pollination; and – provide a landing platform for insects. All the petals together make up the corolla. 6 3  17/7/2024 T5 Reproduction In Plants Parts of a typical flower Receptacle & Pedicel The receptacle is the enlarged end of the flower stalk that bears parts of the flower. The pedicel is the flower stalk. Sessile flowers are flowers without the pedicel and are attached to the plant directly at receptacle pedicel the base. 7 T5 Reproduction In Plants Parts of a typical flower Stamen anther The stamen is the male part of the flower. All the stamens stamen together make up the filament androecium. (plural: androecia) The stamen consists of an anther and a filament. 8 4  17/7/2024 T5 Reproduction In Plants Parts of a typical flower Stamen pollen sacs The filament holds the anther in a suitable position to disperse pollen grains. The anther produces pollen grains. It is made up of two pollen grains lobes, each containing two pollen sacs. anther lobes The anther contains a vascular bundle made up of a phloem and a xylem. 9 T5 Reproduction In Plants Parts of a typical flower Stamen Pollen grains have a haploid set of chromosomes. Each pollen grain has two nuclei, the generative nucleus and the pollen tube nucleus or vegetative nucleus. 10 5  17/7/2024 T5 Reproduction In Plants Parts of a typical flower Carpel (collective: pistil) stigma The carpel is the female part of the flower. style All the carpels together carpel make up the pistil or ovary gynoecium. (plural: gynoecia) The carpel consists of an ovary, a style and one or more stigmas. 11 T5 Reproduction In Plants Parts of a typical flower Carpel (collective: pistil) stigma The stigma is a swollen structure that receives pollen grains. style A mature stigma secretes carpel sugary fluid to stimulate the ovary germination of pollen grains. The style connects the stigma to the ovary. It holds the stigma in a suitable position to trap pollen grains. 12 6  17/7/2024 T5 Reproduction In Plants Parts of a typical flower Carpel (collective: pistil) The ovary contains one or more ovules. The ovule contains the ovum and the definitive nucleus. definitive nucleus The ovum has a haploid set ovary of chromosomes. ovum The ovule is attached to the ovule placenta by a stalk called the funicle. funicle The ovule develops into a placenta seed after fertilization. It produces the haploid female gamete or ovum by meiosis. 13 BL2131 Foundation in Biology II Part II (Pollination) Topic 5: Reproduction in flowering plants 14 14 7  17/7/2024 Learning objectives ❑Outline the process of pollination and distinguish between self-pollination and cross-pollination. ❑Application: Practical 3: Examine the different floral parts of flowering plants, including pollen grains. Compare the differences between insect-pollinated and wind- pollinated flowers. 15 Fundamental Questions A. Do all flowers have 4 whorls? B. What is pollination? C. What are the 2 types of pollination? 16 8  17/7/2024 A. (i) Identify the 4 whorls (circular pattern) of a complete (bisexual / complete) flower from its top view 17 (ii) Identify the 4 whorls of the Hibiscus. 18 9  17/7/2024 (iii) Why do incomplete flowers do not have 4 whorls? They lack one or more floral organs, for example stamens or carpels. Boxelder-maple flowers Left: stamens (male) Right: pistil/carpel (female) (in drooping clusters; have long pedicels that increase exposure of the pollens to the wind) 19 Single Flowers versus Inflorescences Roses Buckeye Cow grass An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated Hibiscus arrangement of branches. 20 20 10  17/7/2024 What are the structural features of the flowers that attract the pollinators? (i) Identify the nectar guides! An Orchid 21 21 What are the structural features of the flowers that attract the pollinators? (ii) Heavily scented flowers are easily found by nocturnal animals. What about flowers that are inconspicuous and odourless? These flowers rely on wind for pollination. 22 22 11  17/7/2024 What are the structural features of the flowers that attract the pollinators? (iii) Why are colours important for flowers too? 23 23 What are the structural features of the flowers that attract the pollinators? (iii) Why are colours important for flowers too? 24 24 12  17/7/2024 Besides colour & size of petals, scent – fragrance smell Left: Michelia champaca from NUS High 25 Which parts of the flowers do you eat? Stamen Pistil http://images.slideplayer.com/7/1727586/slides/slide_40.jpg 26 13  17/7/2024 B. What is pollination? transfer of pollen grains from the anther to the stigma 27 B. What is pollination? Purpose? 28 14  17/7/2024 C. What are the 2 types of pollination? Transfer of pollen grains from one plant Cross to the stigma of a flower in another plant pollination of the same species. Transfer of pollen grains from the anther Self to the stigma of the same flower or of a pollination different flower on the same plant. Self pollination 29 17.3 Pollination Self-pollination Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or a different flower on the same plant. anther transfer of Flowers are bisexual with pollen grains anthers and stigmas maturing at the same time. The stigma is situated directly below the anther. Certain flowers in bisexual stigma plants never open (cleistogamous) and only self- pollination can happen. 30 15  17/7/2024 17.3 Pollination Beneficial qualities are passed down from parent plant to offspring. Only one Advantages of Not dependent on parent is external factors for required. self-pollination pollination. Less pollen and energy More likely to take place since is wasted. stigmas are closer to anthers. 31 17.3 Pollination Offspring produced are genetically similar to parents causing fewer varieties of offspring. Disadvantages of self-pollination Probability of harmful recessive alleles being expressed in offspring is higher as compared with cross-pollination. 32 16  17/7/2024 17.3 Pollination Cross-pollination Cross-pollination involves the transfer of pollen grains to the flower of another plant of the same species. Dioecious plants bear either male or female flowers making anther self-fertilisation impossible. transfer of In bisexual plants, cross- pollen grains pollination can happen when: anthers and stigmas mature stigma at different times. Stigmas of plants are situated at a distance away from the anthers. 33 17.3 Pollination More varieties of offspring Increased probability are produced which leads to of offspring being greater genetic variation. heterozygous. Offspring can Advantages of inherit beneficial cross-pollination qualities from both parents. Seeds produced are capable of Probability of harmful recessive surviving longer alleles being expressed in before germination. offspring is lower as compared with cross-pollination. 34 17  17/7/2024 17.3 Pollination Two different plants of the Dependant on external same species are required. factors for pollination. Disadvantages of cross-pollination More energy and pollen Less likely to occur as are wasted. compared to self-pollination. 35 Structural features of flowers that carry out self-pollination flowers are bisexual with anthers and stigmas maturing at the same time the stigma is situated directly below the anthers in some plants, the flowers never open 36 18  17/7/2024 Compare flower (a) & (b), explain which characteristics of the structure of flower (b) prevent self-pollination. (a) (b) petal anther stamen filament petal stigma stigma carpel / anthers style pistil sepal ovary style Pedicel (flower stalk) sepal 37 37 To facilitate cross-pollination… plants are dioecious (i.e. having either male or female flowers) (e.g. papaya). Or bisexual flowers’ anthers and stigmas mature at different times. stigmas are situated some distance away from anthers 38 19  17/7/2024 39 40 20  17/7/2024 Types of Pollinators 41 Sexually Deceived 42 21  17/7/2024 Sexually Deceived 43 Bees & Deceitful Plants 44 22  17/7/2024 Specific pollinator (e.g. fig) 45 Nurseries for Pollinators stamen carpel 46 23  17/7/2024 Youtube Videoclips used 47 Youtube Videoclips used Fig wasp and fig fruit – BBC (3’11”): https://www.youtube.com/watch?v=JfkiYfrStrU Richard Dawkins: bees and deceitful plants (1:58): https://www.youtube.com/watch?v=wmgKABRCZpo 48 24  17/7/2024 In Summary Tick  if you are able to carry out the following: ❑What is pollination? ❑Distinguish between self-pollination and cross-pollination. 49 49 Q1. Does sexual reproduction always involves two parents? Not always so for plants. Reason: Many flowering plants are bisexual, with both male and female organs in the same flower. Although most flowering plants have mechanisms that promote cross fertilization and prevent self fertilization, some flowering plants may occasionally carry out self fertilization and thus sexual reproduction is achieved within one parent. 50 25  17/7/2024 Q2. Why do pollen grains have different features? To help them to reach the stigma of another flower so as to achieve cross fertilization. Some are light and produced in large numbers. 51 Q3a. Does self fertilization give rise to identical offspring with no genetic variation? b. Is self fertilization the same as asexual reproduction? Q3a. No. Self fertilization is a sexual reproduction process. Many flowering plants are bisexual, with both male and female organs in the same flower. 3b. No. 52 26  17/7/2024 Link: https://forms.office.com/r/T0GRWLRmSR 53 BL2131 Foundation in Biology II Part III (Double Fertilization) Topic 5: Reproduction in plants 54 54 27  17/7/2024 Learning objectives ❑Describe the growth of pollen tube and its entry into the ovule followed by fertilization. ❑Describe double fertilization in plants. ❑Activity on Germination of pollen tubes 55 Double Fertilization in Plants 56 28  17/7/2024 Fundamental Questions How does the pollen tube penetrate through the style of the flower in order to reach the ovule and fertilize the ovum (egg cell) in ovary? How is double fertilization carried out by flowering plants? How does double fertilization prevent plants from wasting energy? 57 Flipped in-class assignment (formative) View the following video from https://www.youtube.com/watch?v=HLYPm 2idSTE Plant Reproduction in Angiosperms [3.34 mins - 8.04 mins] Complete the following questions as you watch the video. 58 29  17/7/2024 Flipped in-class assignment 2 (formative) 59 Qn. Are pollen grains male gametes? Pollen grains are carriers of male gametes. Each pollen grain has two nuclei, the generative nucleus & the pollen tube nucleus. --Generative nucleus divides into 2 male gametes. 60 30  17/7/2024 Sexual reproduction in flowering plants 61 mature pollen sperm cells (n) tube cell Pollination nucleus & Fertilization stigma pollen tube sperm style tube cell nucleus ovary integuments egg (n) Enlarged view polar nuclei of ovule 62 62 31  17/7/2024 mature pollen sperm cells (n) tube cell Pollination nucleus & What is the purpose of tube Fertilization cell nucleus? It directs the stigma stigma 1. Pollen settles on a mature ______. pollen tube to pollen tube 2. Stigma _secretes ________ a sugary fluid. sperm grow style 3. Pollen grain germinates and downwards produces a pollen tube. tube cell the ovule. nucleus ovary integuments egg (n) Enlarged view polar nuclei of ovule 63 63 mature pollen sperm cells (n) Pollination & Fertilization tube cell nucleus Growth of stigma. pollen tube 1. Pollen settles on a mature __________. 1cm / hour! secretes a sugary fluid. 2. Stigma __________ 3. Pollen grain germinates and produces a pollen tube. stigma Enzymes are secreted to digest the ______and 4. _________ style ____. stigma 5. Pollen tube grows down the style into the ovary, pollen tube enters the _______through ovule the tiny opening (micropyle). sperm style 6. Pollen tube’s tip absorbs the sap and ________ bursts, releasing the _____ two male gametes. tube cell nucleus ovary integuments egg (n) Enlarged view polar nuclei of ovule 64 64 32  17/7/2024 mature pollen sperm cells (n) Pollination & Fertilization tube cell nucleus Growth of pollen tube 1cm / hour! How is double fertilization carried out by flowering plants? one male gamete fuses 7. The nucleus of _______________________ stigma with the nucleus of the ovum to form a zygote. ______________________________________ pollen tube sperm male gamete fuses 8. The nucleus of another___________________ style with the two polar nuclei to form a triploid ________________________________________ (3n) cell that will develop into endosperm in ________________________________________ tube cell nucleus fruit later. How does double fertilization prevent plants from wasting ovary energy? integuments egg (n) Enlarged view polar nuclei of ovule 65 65 Double Fertilization (short) 66 33  17/7/2024 How does double fertilization prevent plants from wasting energy? It ensures that a plant does not invest energy in forming an endosperm for an ovule that has not been fertilized. 67 Double Fertilization (Details) 68 34  17/7/2024 Flower parts Post Fertiliation Changes Ovule Seed Zygote Embryo ( radicle, plumule, cotyledon) Endosperm nucleus Endosperm (present in some seeds, food store is absorbed by the embryo) Ovule stalk Seed stalk Ovary Fruit Ovary wall Fruit wall or pericarp Stigma and style Wither or modified to help in fruit dispersal Stamens Wither and fall off Petals Wither and fall off sepals May persist and modified to help fruit dispersal 69 69 Seeds Endosperm is stored food tissue → embryo growth Mature ovule becomes the seed and ovary becomes the fruit 70 70 35  17/7/2024 Fruit & Seed Development (contains nutrients) endosperm Triploid endosperm cell (3n) ovule ovary fruit flesh integument seed coat zygote embryo (2n) Flower Fruit 71 71 Fruit & Seed Development 72 36  17/7/2024 Development of fruit 73 Development of seed 74 37  17/7/2024 Extension Info Growth of root in a radish seed 75 Extension Info Fruits Encourage seed dispersal. Entice animals to eat them and disperse the seeds. Ovary surrounding the seed matures into a fruit. Seeds form from ovules. Adaptations for seed and fruit dispersal : - Animals - Wind - Water - Explosive action 76 76 38  17/7/2024 Extension Info Dispersals of fruits and seeds Infructescence of a dandelion Source: http://bestamericanpizza.com/explanation-animated-gif-dispersal-of-seeds/ 77 Extension Info Comparing Monocots vs. Eudicots FEATURES MONOCOTS DICOTS Cotyledons 1 2 Leaf venation parallel Net-like Root system Fibrous Tap Number of floral In 3’s In 4’s or 5’s parts Vascular bundle Scattered Arranged in a circle positions Woody or Herbaceous Either herbaceous 78 78 39  17/7/2024 Monocot Eudicot Monocot Eudicot Characteristics Characteristics Characteristics Characteristics Embryos Roots One cotyledon Two cotyledons Root system Taproot (main root) usually fibrous usually present (no main root) Leaf venation Pollen Veins usually Veins usually Pollen grain with Pollen grain with one opening three openings parallel netlike Stems Flowers Vascular tissue Floral organs Floral organs usually usually in in multiples of Vascular tissue usually arranged multiples of three four or five scattered in ring 79 79 Extension Info Monocot Flower parts – groups of 3 80 80 40  17/7/2024 Extension Info Dicot Flower parts – groups of 4 or 5 81 81 Extension Info Floral Diagram & Floral formula 82 41  17/7/2024 Extension Info How to construct a floral diagram? 83 Extension Info What is the Floral diagram of Hibiscus rosa-sinesis? Φ K(5) C5 A(∞) G(5) 84 42  17/7/2024 Extension Info What does the Floral formula of Hibiscus rosa-sinesis: Br. Brl. Φ __ K(5) C5 A(∞) G(5) mean? BR.: Bracteate flowers Brl.: Epicalyx Φ: actinomorphic symmetry __: Bisexual K(5): 5 sepals which are fused C5: 5 petals which are free A(∞): stamens are numerous & filaments are fused G(5): 5 carpels, fused and ovary is superior 85 Extension Info 86 43  17/7/2024 Extension Info Floral formula? Br. Φ P3+3 A3+3 G(3) 87 sporophyte (2n) Extension Info megaspore (n) microspore (n) tube cell nucleus male gametophyte pollen sperm cells (pollen grain) tube (n) (n) female gametophyte (embryo sac) egg cell (n) (n) haploid Flowering Plants diploid 88 88 44  17/7/2024 https://classconnection.s3.amazonaws.com/558/flashcards/183558/j pg/picture21332506068763.jpg 89 In Summary Tick  if you are able to carry out the following: ❑Describe the growth of pollen tube and its entry into the ovule followed by fertilization. ❑Describe double fertilization in plants. 90 90 45  17/7/2024 Learning objectives in earlier lessons i. Define and differentiate between asexual and sexual reproduction. ii. Briefly appreciate the importance of mitosis and meiosis for plant reproduction. iii. Outline the process of pollination and distinguish between self-pollination and cross-pollination. 91 Fibonacci Sequence? 92 46  17/7/2024 Asexual vs Sexual Reproduction 93 47