32.2 Pollination and Fertilization
4 min read•june 14, 2024
Plants have an incredible reproductive system. and are key processes that allow them to create new life. These processes involve the transfer of pollen, the growth of pollen tubes, and the fusion of male and female gametes.
Understanding plant reproduction is crucial for grasping how plants adapt and thrive. From to , and the unique in flowering plants, these processes showcase nature's ingenuity in ensuring plant survival and diversity.
Pollination and Fertilization in Plants
Steps of plant fertilization
Top images from around the web for Steps of plant fertilization
Plant life cycles and taxonomy | It's a natural universe View original
Is this image relevant?
Double Fertilization | Biology for Majors II View original
Is this image relevant?
Plant Reproductive Development and Structure | Boundless Biology View original
Is this image relevant?
Plant life cycles and taxonomy | It's a natural universe View original
Is this image relevant?
Double Fertilization | Biology for Majors II View original
Is this image relevant?
1 of 3
Top images from around the web for Steps of plant fertilization
Plant life cycles and taxonomy | It's a natural universe View original
Is this image relevant?
Double Fertilization | Biology for Majors II View original
Is this image relevant?
Plant Reproductive Development and Structure | Boundless Biology View original
Is this image relevant?
Plant life cycles and taxonomy | It's a natural universe View original
Is this image relevant?
Double Fertilization | Biology for Majors II View original
Is this image relevant?
1 of 3
- involves the transfer of pollen grains from the to the of a flower
- Can occur through (within the same flower or plant) or (between different plants of the same species)
- Examples of pollination agents include wind, water, insects (), and birds ()
- germination occurs when the pollen grain absorbs moisture and nutrients from the stigma
- emerges from the pollen grain and begins to grow through the towards the
- Growth is guided by chemical signals released by the
- Double fertilization is a unique feature of flowering plants ()
- Two sperm cells are released from the pollen tube into the
- One fuses with the egg, forming the which develops into the
- The other sperm cell fuses with two , forming the which provides nutrition for the developing embryo
Self-pollination vs cross-pollination
- Self-pollination involves the transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant
- Leads to genetic uniformity in offspring as they inherit genes from a single parent plant
- Advantageous in stable environments where the parent plant is well-adapted
- Examples of self-pollinating plants include peas, wheat, and tomatoes
- Cross-pollination involves the transfer of pollen grains from the anther of one plant to the stigma of another plant of the same species
- Requires external agents such as wind, water, or animals (insects, birds) for pollen transfer
- Leads to genetic diversity in offspring as they inherit genes from two different parent plants
- Advantageous in changing environments where genetic variability can help plants adapt
- Examples of cross-pollinating plants include apple trees, sunflowers, and grasses
Pollination to seed development
- Pollination occurs when pollen grains are transferred from the anther to the stigma
- Pollen grain germination and pollen tube growth follow pollination
- Pollen grain absorbs moisture and nutrients from the stigma and begins to grow a pollen tube
- Pollen tube grows through the style towards the , guided by chemical signals from the ovule
- Double fertilization takes place once the pollen tube reaches the ovule
- Two sperm cells are released into the embryo sac
- One sperm cell fuses with the egg, forming the zygote
- The other sperm cell fuses with two polar nuclei, forming the endosperm
- Seed development begins after double fertilization
- Zygote develops into an embryo which will become the new plant
- Endosperm provides nutrition for the developing embryo
- Ovule develops into a , protecting the embryo
- Fruit development occurs as the ovary wall matures into a fruit, enclosing the seed(s)
- Examples of fruits include apples, oranges, and cucumbers
Double fertilization in flowering plants
- Double fertilization is a unique feature of flowering plants (angiosperms) that involves the fusion of two sperm cells with different parts of the female
- One sperm cell fuses with the egg, forming the zygote which develops into the embryo
- The other sperm cell fuses with two polar nuclei, forming the endosperm which provides nutrition for the developing embryo
- Significance of double fertilization in flowering plants:
- Ensures the simultaneous development of the embryo and endosperm
- Endosperm provides a food reserve for the developing embryo, supporting its growth
- Allows for the formation of seeds, a key adaptation in the evolutionary success of angiosperms
- Seeds contain an embryo, food reserve (endosperm), and protective coat, enabling plants to disperse and survive in various environments
Reproductive structures and gamete formation
- The is the female reproductive structure of a flower, consisting of the stigma, style, and ovary
- The is the male reproductive structure of a flower, composed of the anther and filament
- Gametes are reproductive cells that carry genetic information:
- Sperm cells are male gametes produced in the anther through the process of microsporogenesis
- Egg cells are female gametes formed in the ovule through megasporogenesis
- Microspores develop into pollen grains, which contain the male gametophyte
- Megaspores develop into the female gametophyte (embryo sac) within the ovule
Key Terms to Review (61)
Accessory fruits: Accessory fruits are fruits in which some of the flesh is derived not from the ovary but from some adjacent tissue exterior to the carpel. These fruits often involve other parts of the flower, such as the receptacle or hypanthium, contributing to the fruit's structure.
Aggregate fruit: An aggregate fruit forms from the merger of several ovaries that were separate in a single flower. They are derived from multiple carpels of one flower and develop into a cluster of smaller fruits joined together.
Aleurone: Aleurone is the outermost layer of the endosperm in seeds, primarily found in cereals. It plays a critical role in seed germination by secreting enzymes that break down stored nutrients for the developing plant.
Amniote embryo: An amniote embryo is an embryo that develops inside an amniotic egg, which provides a protective environment. This adaptation is crucial for terrestrial reproduction among vertebrates such as reptiles, birds, and mammals.
Angiosperms: Angiosperms, also known as flowering plants, are a group of vascular plants that produce flowers and seeds enclosed within a fruit. This group represents the most diverse and widespread category of plants on Earth, playing crucial roles in ecosystems and human agriculture through their varied forms and functions.
Anther: An anther is the part of a stamen in flowering plants that produces and holds pollen, which is crucial for reproduction. Located at the top of the filament, the anther is typically bulbous and often has a two-lobed structure. It plays a significant role in angiosperm reproduction by releasing pollen grains for transfer to the female reproductive structures, enabling fertilization.
Bees: Bees are flying insects that belong to the superfamily Apoidea, known for their role in pollination and honey production. They are essential pollinators for many flowering plants, facilitating the transfer of pollen from male to female reproductive structures, which is crucial for plant fertilization and seed production. Their behavior and social structure, particularly in species like honeybees, also play a vital role in ecosystem health and agricultural productivity.
Coleoptile: The coleoptile is a protective sheath covering the emerging shoot in monocotyledons, such as grasses. It plays a crucial role in shielding the young shoot as it grows upward through the soil.
Coleorhiza: Coleorhiza is a sheath-like structure that protects the radicle in monocot seeds during germination. It helps in anchoring the seedling to the soil as the radicle grows out.
Cotyledons: Cotyledons are the first leaves that appear on a seedling. They play a crucial role in the early stages of plant development by providing nutrients to the young plant before true leaves begin photosynthesis.
Cross-pollination: Cross-pollination occurs when pollen from the anther of one flower is transferred to the stigma of another flower, often of the same species. This process promotes genetic diversity within a plant population.
Cross-pollination: Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower, leading to fertilization and genetic diversity. This process is essential for many flowering plants, including seed plants, as it promotes genetic variation that can enhance adaptability and survival. Cross-pollination occurs through various agents, such as wind, water, and animals, which help facilitate this vital reproductive process.
Dormancy: Dormancy is a state in which a plant temporarily stops growing and reduces its metabolic activities to conserve energy. This often occurs in response to adverse environmental conditions such as extreme temperatures or insufficient water supply.
Double fertilization: Double fertilization is a unique reproductive process in flowering plants where one sperm cell fertilizes the egg cell to form a zygote, while another sperm cell fuses with two polar nuclei to create a triploid cell that develops into the endosperm. This process is crucial for the development of seeds in angiosperms and ensures that the embryo has a nutritious food source as it grows. By creating both a zygote and endosperm, double fertilization supports the complex reproductive structures and strategies found in flowering plants.
Egg cell: An egg cell, or ovum, is the female reproductive cell in organisms that reproduce sexually. It is typically larger than the male sperm cell and carries half of the genetic information necessary for fertilization. The egg cell plays a critical role in reproduction, as it must be fertilized by a sperm cell to form a zygote, which then develops into an embryo.
Embryo: An embryo is an early developmental stage of a multicellular organism, particularly in the context of seed plants and animals, where it develops from the fertilized egg. This stage is crucial as it involves significant cellular division and differentiation, leading to the formation of various tissues and organs. In seed plants, the embryo is contained within the seed and plays a key role in the plant's reproductive cycle.
Embryo sac: The embryo sac is the female gametophyte of flowering plants, which contains the egg cell and is essential for sexual reproduction. It develops within the ovule and plays a crucial role in the processes of fertilization and seed development. The structure of the embryo sac is intricately linked to reproductive development, as it houses the necessary cells that will participate in forming the next generation of plants.
Endocarp: The endocarp is the innermost layer of the pericarp that surrounds and protects the seed(s) within a fruit. It can be hard or soft depending on the type of fruit.
Endosperm: Endosperm is a tissue found in seeds of flowering plants that provides nourishment to the developing embryo. It plays a critical role in seed development and germination, supplying the necessary nutrients for the growth of the young plant. The formation of endosperm is a key evolutionary adaptation that supports the reproductive success of seed plants, particularly angiosperms, enhancing their role in diverse ecosystems.
Endospermic dicots: Endospermic dicots are a type of dicotyledonous plant where the seeds retain some endosperm at maturity. This endosperm provides nutrients to the developing embryo within the seed.
Epicotyl: The epicotyl is the part of a seedling that lies above the cotyledons (seed leaves) and below the first true leaves. It is crucial for the initial vertical growth of the young plant after germination.
Exocarp: The exocarp is the outermost layer of the pericarp, which is the part of a fruit formed from the ovary wall. It serves as a protective layer for the fruit and can vary in texture and thickness.
Fertilization: Fertilization is the biological process where male and female gametes unite to form a zygote, marking the beginning of a new organism's development. This event is crucial for sexual reproduction, involving the combination of genetic material from two parents, which contributes to genetic diversity and evolutionary processes.
Gamete: A gamete is a specialized reproductive cell that carries half the genetic information of an organism, combining with another gamete during fertilization to form a new organism. Gametes are crucial for sexual reproduction and play a key role in genetic diversity and inheritance.
Gametophyte: A gametophyte is the haploid stage in the life cycle of plants and some algae that produces gametes (sperm and eggs) through mitosis. This phase alternates with the diploid sporophyte generation, and the gametophyte plays a crucial role in sexual reproduction and the development of new organisms.
Hummingbirds: Hummingbirds are small, colorful birds known for their rapid wing beats and ability to hover in mid-air, making them essential pollinators for many flowering plants. Their unique feeding behavior, where they extract nectar from flowers, promotes the process of pollination, allowing plants to reproduce. This relationship is crucial in maintaining biodiversity and ecosystem health, as hummingbirds facilitate the fertilization of various plant species.
Hypocotyl: The hypocotyl is the stem-like structure found between the seed leaves (cotyledons) and the root in a developing plant embryo. It plays a crucial role in early seedling growth by pushing the cotyledons above the soil surface during germination.
Megaspore: A megaspore is a large spore that develops into a female gametophyte in seed plants, particularly in the context of gymnosperms and angiosperms. It plays a crucial role in the reproductive cycle, as it is produced by the megasporangium and undergoes meiosis to produce the female gametes, which are essential for fertilization and the formation of seeds.
Mesocarp: The mesocarp is the fleshy middle layer of a fruit's pericarp, located between the outer exocarp and the inner endocarp. It is typically the part of the fruit that is eaten and can vary in texture and thickness depending on the type of fruit.
Microspore: A microspore is a haploid spore that develops into a male gametophyte in seed plants and some other vascular plants. These tiny spores are crucial for reproduction, as they give rise to pollen grains which carry the male gametes necessary for fertilization. In gymnosperms, microspores are produced in the male cones and play a key role in their reproductive structures, while in flowering plants, they also contribute to the formation of pollen.
Multiple fruit: A multiple fruit develops from an inflorescence, a cluster of flowers each with its own ovary, that merge into a single mass. Examples include pineapples and figs.
Nectar guide: Nectar guides are visual patterns on flowers that direct pollinators to the nectar source. These guides often appear as color contrasts or ultraviolet markings invisible to the human eye.
Non-endospermic dicots: Non-endospermic dicots are flowering plants whose seeds lack an endosperm at maturity. Instead, the cotyledons serve as the main storage tissue for nutrients.
Ovary: The ovary is the female reproductive organ of a flower that develops into a fruit after fertilization. It contains ovules, which become seeds upon fertilization.
Ovary: An ovary is a female reproductive organ that produces ova (egg cells) and hormones such as estrogen and progesterone. In plants, the ovary is part of the flower's pistil and contains ovules that develop into seeds after fertilization. This structure is essential for sexual reproduction, connecting to various life cycles and reproductive strategies.
Ovule: An ovule is a structure found in seed plants that contains the female gametophyte and develops into a seed after fertilization. It is critical for sexual reproduction as it houses the egg cell and, upon successful fertilization, transforms into a seed, ensuring the continuation of the plant species. The evolution of ovules marked a significant advancement in plant reproduction, providing protection to the developing embryo and facilitating the transition to seed plants.
Pericarp: The pericarp is the part of a fruit that develops from the ovary wall after fertilization. It typically consists of three layers: the exocarp, mesocarp, and endocarp.
Pistil: The pistil is the female reproductive structure of a flower, consisting of the ovary, style, and stigma. It plays a critical role in reproduction by facilitating the processes of pollination and fertilization, allowing for the development of seeds and fruit. The pistil is essential for plant reproduction, as it houses the ovules and serves as the site where pollen grains germinate and fertilization occurs.
Plumule: The plumule is the part of a seed embryo that develops into the shoot bearing the first true leaves. It emerges above the soil during germination and is crucial for photosynthesis initiation.
Polar nuclei: Polar nuclei are two haploid nuclei found within the central cell of an ovule in flowering plants, playing a critical role during fertilization. They contribute to the formation of the triploid endosperm when fertilized by one sperm cell, while the other sperm cell fuses with the egg cell to form the diploid zygote. Understanding polar nuclei is essential for grasping how plants reproduce and develop their seeds and fruits.
Pollen grain: A pollen grain is a microscopic structure produced by seed plants that contains the male gametes for fertilization. These grains play a crucial role in the reproduction of gymnosperms and angiosperms, as they are involved in the process of pollination, which allows for the transfer of sperm to the ovule for fertilization. Pollen grains are typically designed for dispersal by wind or animals, ensuring genetic diversity and successful reproduction.
Pollen tube: A pollen tube is a slender, tubular structure that forms after a pollen grain lands on a compatible stigma, allowing the sperm cells to travel from the male gametophyte to the ovule for fertilization. This process is critical in the reproductive cycle of seed plants, as it ensures that fertilization occurs efficiently and effectively. The pollen tube serves as a bridge, connecting the pollen grain to the ovule, facilitating the transfer of genetic material necessary for the development of seeds.
Pollination: Pollination is the transfer of pollen from the male anther to the female stigma of a flower. This process is essential for the fertilization and subsequent development of seeds in seed plants.
Pollination: Pollination is the transfer of pollen grains from the male anther of a flower to the female stigma, facilitating fertilization and the development of seeds. This process is crucial for the reproduction of angiosperms, as it ensures genetic diversity and successful seed formation. The interaction between pollinators and plants also impacts ecological balance and biodiversity.
Radicle: The radicle is the embryonic root of a plant that emerges from the seed during germination. It is the first part of a seedling to grow and anchors the plant in the soil while absorbing water and nutrients.
Scarification: Scarification is the process of weakening, opening, or altering the coat of a seed to encourage germination. It can be achieved through mechanical, thermal, or chemical means.
Scutellum: The scutellum is a specialized, shield-like cotyledon found in the embryos of grass family plants, such as maize and wheat. It facilitates the absorption of nutrients during seed germination.
Seed coat: The seed coat is the protective outer layer of a seed that encases the developing embryo and stored nutrients. This structure plays a critical role in the survival and development of seed plants by safeguarding the embryo from physical damage and desiccation, while also facilitating the seed's dispersal and germination processes.
Self-pollination: Self-pollination is the transfer of pollen from the anther to the stigma of the same flower or another flower on the same plant. It results in offspring genetically similar to the parent plant.
Self-pollination: Self-pollination is the process where pollen from the anther of a flower fertilizes the ovule of the same flower or another flower on the same plant. This mechanism allows for reproduction without the need for external pollinators, making it an important reproductive strategy for many plants, especially those in environments where pollinator availability is limited. Self-pollination can lead to offspring that are genetically similar to the parent plant, which can be advantageous in stable environments but may limit genetic diversity.
Simple fruit: A simple fruit develops from a single ovary of a single flower. Examples include berries, drupes, and pomes.
Sperm cell: A sperm cell is the male gamete responsible for sexual reproduction in many organisms, including plants and animals. This specialized cell carries genetic information from the male parent and is designed to fertilize an egg, leading to the formation of a zygote. Sperm cells are crucial in the process of pollination and fertilization as they travel to the female reproductive structures to achieve successful reproduction.
Stamen: The stamen is the male reproductive part of a flower, responsible for producing pollen, which contains the male gametes. Each stamen typically consists of two main parts: the anther, where pollen is formed, and the filament, which supports the anther and holds it in position for effective pollination. This structure is vital for the reproduction of flowering plants and plays a significant role in the evolution and diversity of seed plants.
Stamens: Stamens are the male reproductive organs of a flower, consisting of an anther and a filament. They produce and release pollen necessary for fertilization.
Stigma: The stigma is the part of the female reproductive structure of flowering plants where pollen grains land and germinate. It plays a critical role in reproduction by receiving pollen during pollination, which is essential for fertilization and the development of seeds. The structure is often sticky or feathery, adapted to enhance the likelihood of successful pollination by attracting pollen from various sources.
Style: In botany, the style is a slender, elongated structure in flowering plants that connects the stigma to the ovary. It plays a crucial role in the reproductive process by facilitating the movement of pollen tubes from the stigma to the ovules contained within the ovary, ensuring successful fertilization. The style also influences the reproductive development and structure of angiosperms, aiding in the pollination process.
Suspensor: The suspensor is a structure in seed plants that connects the developing embryo to the nutrient-rich tissue of the seed. It helps in nutrient transfer and supports early embryonic growth.
Tegmen: The tegmen is the inner protective layer of a seed coat in flowering plants. It surrounds the embryo and works in conjunction with the outer layer, known as the testa.
Testa: The testa is the outer protective layer of a seed. It shields the seed from physical damage and pathogens during dormancy and germination.
Vernalization: Vernalization is the process by which prolonged exposure to cold temperatures prompts flowering in certain plants. This physiological response ensures that flowering occurs at a favorable time, typically in spring.
Zygote: A zygote is the initial cell formed when two gametes, typically a sperm and an egg, fuse during fertilization. This single cell undergoes division and development, leading to the formation of a new organism, making it a crucial stage in sexual reproduction across various life forms.