Flowers, Fruits, and Seeds Lecture PDF

FLOWERS, FRUITS, AND SEED’S Lecture Asexual Reproduction in Plants INTRODUCTION Other Methods: Some plants can Ragweed (Ambrosia) is one of the reproduce asexually throu...

FLOWERS, FRUITS, AND SEED’S Lecture Asexual Reproduction in Plants INTRODUCTION Other Methods: Some plants can Ragweed (Ambrosia) is one of the reproduce asexually through most freqeuntly encountered stems, leaves, or roots, weeds in the northeastern and bypassing the need for flowers. central parts. o Characteristics: In Pollen comes from flowers, the asexual reproduction, there organs of reproduction in most is only one parent, and no plants. fusion of gametes occurs, Flowering plants, or angio sperms: leading to offspring that are They reproduce both sexually and genetically identical to the asexually. parent. REPRODUCTIVE FLEXIBILTY OF FLOWERS FLOWERIN PLANTS Flower: A Reproductive Shoot Key Components: A flower BIOLOGICAL FUNCTION OF consists of four types of organs: FLOWERS: Sexual Reproduction o Sepals, Petals, Stamens, ○ Main purpose: Flowers are and Carpels. specialized structures for Peduncle (Flower Stalk) sexual reproduction in Arrangement of Organs: The plants. organs are arranged in whorls (circular patterns) on the peduncle. Adaption of Flowers Inflorescence ○ Colors, Shapes, and Flower Cluster: The peduncle can Fragrances: Flowers have end in either a single flower or a evolved a variety of vibrant cluster of flowers, known as an colors, distinct shapes, and inflorescence. pleasant scents to attract Organ Order (From Outer to Inner pollinators, increasing the Layers) chances of transferring The order of the organs from the pollen from one plant to flower’s outer edge to the center: another. 1. Sepals Fertilization Process: 2. Petals o Fusion of Gametes: 3. Stamens Fertilization involves the fusion 4. Carpels of the plant's reproductive cells, Receptacle the egg cell (female gamete) Support Structure: The receptacle and the sperm cell (male is the enlarged tip of the peduncle, gamete). where some or all flower parts are attached. Flower Types Based on Organ ○ Location: This process Completeness occurs within the flower's Complete Flower: Contains all ovary, resulting in the four parts—sepals, petals, development of seeds. stamens, and carpels. Incomplete Flower: Lacks one or more of these parts. Flower Types Based on Reproductive Organs Perfect Flower: Contains both stamens (male reproductive 1 FLOWERS, FRUITS, AND SEED’S Lecture organs) and carpels (female reproductive organs). PARTS OF A FLOWER( for sexual Imperfect Flower: Contains either reproduction) stamens or carpels, but not both. Sepal Pollen Transfer: For sexual reproduction Function: The sepal is one of the to occur, pollen grains must be transferred outermost parts of a flower, often from the anther (male) to the carpel resembling a leaf. It plays a (female) of the same species. protective role, shielding the flower when it is still a bud. Pollen Grain Structure: Each Petals Description: Petals are often the pollen grain consists of two cells brightly colored parts of a flower, enclosed in a tough outer wall. One located inside the whorl of sepals. cell generates two male gametes Stamens (Male Reproductive (sperm cells). Organs) Location: Stamens are located Carpels (Female Reproductive Organs) inside and above the petals. Function: The carpel bears Parts of a Stamen: ovules, structures that can develop o Filament: A thin stalk that into seeds after fertilization. supports the anther. o A single carpel or a group of o Anther: The structure at the fused carpels is sometimes top of the filament, where referred to as a pistil (if pollen grains are produced. single) or compound pistil o Pollen Grains: Small, sac- (if fused) like structures that contain the male reproductive cells. CARPEL (THREE MAIN PARTS) Stigma: The top part of the carpel, which IMPORTANT INFO captures pollen grains. Reproductive Organs: Only stamens and carpels directly participate in sexual Style: A neck-like structure through which reproduction. the pollen tube grows to reach the ovary. Sterile Organs: Sepals and petals are sterile and do not participate in Ovary: A jug-like structure at the base of reproduction. the carpel that contains one or more ovules, which can develop into seeds after fertilization. PARTS OF A FLOWER: Ovule: Contains the female gametophyte (also known as the embryo sac) that develops into the female gamete. Ovary Types Superior Ovary: An ovary where other floral organs (sepals, petals, and stamens) are free from the ovary and attached at its base. Inferior Ovary: An ovary located below the point where other floral 2 FLOWERS, FRUITS, AND SEED’S Lecture organs are attached, appearing genetic diversity and negatively embedded in the receptacle. affect the plant's health. Self-Incompatibility Preventing Self-Pollination: POLLINATION Many plant species have developed self-incompatibility Pollination mechanisms to avoid self- Definition: In seed plants, pollination and promote cross- pollination is the process of pollination. These mechanisms transferring pollen grains from the prevent the plant from accepting its anther (male part) to the stigma own pollen, thus encouraging (female part). genetic diversity and healthier offspring. Types of Pollination Self-Pollination: This occurs when FLOWERING PLANTS AND THEI pollen is transferred within the POLLINATORS same flower or between different flowers on the same plant. Cross-Pollination: This happens Coevolution when pollen grains are transferred Definition: Coevolution refers to to a flower on a different plant of the process where two species the same species. interact so closely that they undergo reciprocal adaptations, becoming increasingly specialized to each other over time. Prevent self-Pollination Animal-Pollinated Flowers How Flowers Attract Pollinators: Pollination Showy Petals: Brightly colored Definition: In seed plants, petals serve as visual attractants. pollination is the process of Scent: Fragrances (olfactory transferring pollen grains from the attractants) lure pollinators, anther (male part) to the stigma especially those with a strong (female part). sense of smell. Types of Pollination Rewards for Pollinators Self-Pollination: This occurs when Nectaries: Special floral glands pollen is transferred within the produce a sugary solution called same flower or between different nectar, which pollinators consume flowers on the same plant. as an energy-rich food source. Cross-Pollination: This happens Pollen: In addition to nectar, pollen when pollen grains are transferred grains provide pollinators with a to a flower on a different plant of protein-rich food source. the same species. IMPORTANT INFO Prevent self-Pollination Bee-Pollinated Crops: Bees pollinate crops that provide around Inbreeding and Self-Incompatibility in 30% of the world’s human food Plants supply. Inbreeding: In some plants, Color Adaptations: Plants repeated self-pollination can lead to pollinated by insects, especially inbreeding, which may reduce bees, often have blue or yellow 3 FLOWERS, FRUITS, AND SEED’S Lecture The other sperm cell fuses with two petals to attract them. other nuclei in the ovule, forming "Bee Purple": Bees can see a the endosperm, which provides range of ultraviolet light known as nourishment for the developing "bee purple," which makes certain seed. patterns on petals visible to them. Seed and Fruit Development: The fertilized ovule develops into a Nectar Guides: Some flowers have seed, containing the embryo and patterns or markings (nectar endosperm. guides) that direct pollinators The surrounding ovary matures toward the nectar. into a fruit, which protects the Insect Adaptation: Insects, seeds and aids in their dispersal. particularly those with a well- developed sense of smell, are highly adapted to locating flowers by scent. EMBRYONIC DEVELOPMENT IN SEEDS IS ORDERLY AND PREDICTABLE Seed Formation: In flowering WIND POLLINATED PLANTS plants, a fertilized ovule develops into a compact seed, containing a -Wind pollinated plants young plant embryo and stored - produce small and inconspicuous nutrients. This occurs after flowers. fertilization, when the pollen grain -Wind pollinated plants produce a large germinates on the stigma, and the quantities of pollen grains, which increases pollen tube grows through the style the likelihood of that some pollen grains will and ovary to reach the female land on the appropriate stigma. gametophyte (embryo sac) in the ovule. FERTILIZATION AND SEED AND FRUIT DEVELOPMENT STRUCTURE OF A MATURE SEED Pollen Tube Formation: Embryonic Plant and Storage: A After pollination, the tube cell mature seed contains: within the pollen grain grows into a o An embryonic plant. pollen tube. o Stored nutrients, either in The pollen tube extends down the endosperm or in the through the style towards the ovary, cotyledons. creating a path for fertilization. Endosperm: The endosperm is the Generative Cell: nutritive tissue that surrounds and The generative cell inside the nourishes the embryonic plant pollen grain divides to produce two within the seed. sperm cells. Seed Coat: The seed is encased in These sperm cells travel down the a tough, protective outer layer pollen tube to reach the ovule in the called the seed coat. ovary. Fertilization: COMPONENTS OF THE EMBRYONIC Once the pollen tube reaches the PLANT ovule, one sperm cell fertilizes the egg cell, forming a zygote (which develops into an embryo). 4 FLOWERS, FRUITS, AND SEED’S Lecture Radicle (Embryonic Root): The part of the embryo that will develop into the plant’s FRUITS ARE MATURE. RIPENED root system. OVARIES Embryonic Shoot: The portion of the embryo that will develop into the plant’s stem and leaves. Fruit Development After Fertilization Hypocotyl: The short part of the Once fertilization occurs within the embryonic shoot that connects the ovule, the ovule develops into a radicle to the cotyledons. seed, while the surrounding ovary Plumule (Epicotyl): The shoot matures into a fruit. apex above the cotyledons, which A single fruit may contain one or will develop into the first true more seeds, depending on the type leaves. of fruit. Cotyledons (Seed Leaves): Monocots: Plants with a single cotyledon. Four Basic Types of Fruits Eudicots: Plants with two 1. Simple Fruit: cotyledons o Develops from a single carpel or several fused AFTER THE RADICLE, carpels. HYPOCOTYL,COTYLEDONS, AND o At maturity, simple fruits PLUMULE HAVE FORMED may be fleshy or dry. Germination Process: o Example: A berry is a type Radicle: The radicle is the first part of fleshy simple fruit. to emerge from the seed during 2. Aggregate Fruit: germination. It grows downward, o Forms from a single flower developing into the primary root, that has multiple free anchoring the plant, and absorbing carpels, each developing water and nutrients from the soil. into a small fruit that collectively forms a larger Hypocotyl: The hypocotyl fruit. elongates and pushes the 3. Multiple Fruit: cotyledons above the soil surface. o Develops from the carpels This process is known as hypogeal of several closely germination (if the cotyledons associated flowers that fuse remain below ground) or epigeal together as the fruit germination (if the cotyledons matures. emerge above ground). 4. Accessory Fruit: o A fruit in which the fleshy part develops from tissue Cotyledons: The cotyledons other than the ovary, such provide stored nutrients to the as the receptacle. developing plant until the first true leaves form and photosynthesis Types of Specialized Simple Fruits begins. Once the true leaves are Pepo: A modified berry with a established, the cotyledons leathery rind. Examples include typically wither and fall off. pumpkins, squash, cucumbers, and watermelons. Plumule (Epicotyl): After the Hesperidium: A type of fruit with a hypocotyl emerges, the plumule leathery rind that contains continues to grow, producing the numerous oil glands. Inside, first true leaves, which take over the succulent cavities hold the seeds. role of photosynthesis to support Citrus fruits like oranges and further growth of the seedling. lemons are examples. 5 FLOWERS, FRUITS, AND SEED’S Lecture Drupe: A fleshy or fibrous fruit that clustered flowers. Examples has a hard stone (or pit) include pineapples and figs. surrounding a single seed. Examples include peaches, cherries, avocados, olives, and SEED DISPERSAL IS HIGLY VARIED almonds. Seed dispersal is crucial for plant Dry Simple Fruits reproduction and species survival, allowing Many simple fruits dry out at seeds to spread and grow in new locations. maturity. Some of these are Plants have evolved various methods to dehiscent, meaning they split open disperse seeds, each suited to different to release seeds, while others are environments and conditions. indehiscent, meaning they do not split open. Types of Seed Dispersal Dehiscent Dry Fruits: 1. Wind Dispersal (Anemochory): o Follicle: A fruit that splits o Seeds are light, often with open along one seam specialized structures like (suture) to release seeds. wings or plumes, allowing Example: milkweed. them to be carried by the o Legume: A fruit that splits wind. open along two seams. o Examples: Dandelions, Example: pea pods and maples, and pine trees. beans. 2. Water Dispersal (Hydrochory): o Capsule: A fruit that splits o Seeds float and are carried open along multiple sutures away by water currents. or pores. Examples include This method is common in iris, poppy, buckeye, and plants that live near bodies cotton fruits. of water. Indehiscent Dry Fruits: o Examples: Coconuts, o Caryopsis: Resembles a water lilies. seed; the fruit wall is fused 3. Animal Dispersal (Zoochory): to the seed coat. Examples: o External Dispersal: Some corn and wheat kernels. seeds have hooks, spines, o Nut: A simple dry fruit with a or sticky surfaces that hard, stony wall that does attach to the fur, feathers, or not split open at maturity. skin of animals, which carry Examples include acorns the seeds to new locations. and hazelnuts. ▪ Examples: o Achene: Similar to a Burdock, beggar- caryopsis but with the seed ticks. attached to the fruit wall at o Internal Dispersal: only one point. Example: Animals eat fruits and later sunflower seeds. excrete the seeds in new areas. This method often Aggregate and Multiple Fruits involves fleshy fruits that Aggregate Fruits: Formed from a attract animals. single flower that has several ▪ Examples: Berries, separate carpels, each developing apples, cherries. into a small fruit. Example: 4. Gravity Dispersal (Barochory): strawberries. o Seeds simply fall from the Multiple Fruits: Develop from the plant due to gravity. These fused carpels of several closely seeds often rely on rolling or bouncing to spread. 6 FLOWERS, FRUITS, AND SEED’S Lecture o Examples: Chestnuts, acorns. Stages of Seed Germination 5. Explosive Dispersal 1. Imbibition: (Ballochory): o The seed absorbs water, o Some plants have seed causing it to swell and break pods that burst open the seed coat. forcefully, ejecting seeds 2. Enzyme Activation: over considerable o Water activates enzymes distances. within the seed, which break o Examples: Touch-me-nots down stored nutrients in the (Impatiens), witch hazel, endosperm or cotyledons. and violets. These nutrients provide energy for the growing SEED GERMINATION AND EARLY embryo. GROWTH 3. Radicle Emergence: o The radicle (embryonic Conditions Required for Germination root) is the first structure to 1. Water: emerge, growing downward o Water is essential for into the soil to anchor the germination as it activates seedling and absorb water enzymes that begin the and nutrients. growth process. Seeds 4. Shoot Emergence: absorb water through a o After the radicle, the process called imbibition, hypocotyl pushes the causing the seed to swell shoot (including the and break the seed coat. plumule) upward. 2. Temperature: Depending on the type of o Seeds require a specific germination: temperature range to ▪ In epigeal germinate. Some seeds germination, the prefer warm conditions, hypocotyl elongates, while others may need and the cotyledons cooler temperatures. The are pulled above the right temperature triggers soil surface. the biochemical processes ▪ In hypogeal necessary for growth. germination, the 3. Oxygen: cotyledons remain o Oxygen is needed for below the soil cellular respiration, which surface, and only provides the energy the epicotyl grows required for the growth of above ground. the seedling. 5. Cotyledon Expansion: 4. Light: o The cotyledons provide o Some seeds need exposure stored nutrients to the to light to germinate, while seedling until it can perform others germinate better in photosynthesis. darkness. This varies 6. Plumule Development: between species. o The plumule (young shoot) develops into the first true leaves. Once these leaves unfold, the seedling begins photosynthesis, creating its own food. 7 FLOWERS, FRUITS, AND SEED’S Lecture Coleoptile: A protective sheath in monocots that helps the shoot push through the soil. Indeterminate Growth: Growth that continues indefinitely, often found in perennials, trees, and some vegetables like tomatoes. Determinate Growth: Growth that ceases once the plant or organ reaches its mature size, commonly seen in bush plants and some annual crops. 8