Which part of a plant produces pollen? | Reference.com Which part of a plant produces pollen? A: Quick Answer The stamen is the part of a flower that produces pollen. The anther, which is supported by a filament, is the part of the stamen where the pollen is produced. Full Answer Ovules are produced in the ovary in the base of the female part of the flower, called the pistil. When the ovary is mature, it is called a fruit. Mature ovules are called seeds. For pollination to occur, pollen must move from the stamen to the stigma, which is the top of the pistil. Wind, hummingbirds, bees and butterflies help pollinate flowers. Plants that depend on wind pollination often have long stamens and pistils. What Part of a Plant Makes Pollen? | Garden Guides What Part of a Plant Makes Pollen? What Part of a Plant Makes Pollen? Reason for flagging? Submit Overview Although some people are allergic to pollen, the role pollen plays in the life cycle of a plant is nothing to sneeze at.

Flowering plants, called angiosperms, produce pollen in a male floral part called the stamen, comprised of a stem-like filament and pollen-shedding pod called the anther. In non-flowering plants, called gymnosperms, pollen is made in male-gendered cones. Flower Parts Flowering plants, or angiosperms, create structures to exchange genetic codes in the process of making seeds. Flowers are this specialized structure. Although flowers may have both male and female floral parts, some plant species have flowers that are single-gendered, having male or female parts in separate flowers. The female part of the flower is known as the pistil and is generally found in the center of the flower. The pistil is comprised of stigma, the style and the ovary. The male part of the flower is known as the stamen and usually surrounds the female pistil. The Stamen The individual male floral part is referred to as the stamen, or androecium. A stamen is made up of a thin stem called a filament and pollen-filled sacs called an anther. Often each flower has multiple stamens. The Filament A filament is a thin, thread-like stalk of the stamen.

It physically supports and carries the pollen-making anther at its tip, providing a means for water, nutrients and hormones to permit the development of the anther as the flower matures. The Anther At the tip of the stamen's filaments is the anther, which is a single or collection of pollen sacs where pollen is created, ripened and released. A pollen grain is minute in size and is shaped uniquely per each plant species. Pollen Each pollen grain is filled with male gametophytes of the plant. A gametophyte contains the genetic code, DNA, of the plant in one-half the amount. Once a pollen grain reaches and fertilizes the ovary of the female flower part, the two halves of the DNA code merge and form a viable seed that can later develop into a plant. Cones In non-flowering plants, called gymnosperms, no flowers are produced, but reproduction takes place via differently gendered cones. Cycads and conifers like pines and spruces are an example. Male cones are small, thin, cylindrical structures that spilt open to shed copious amounts of pollen. Wind carries this pollen, distributing it upon nearby female cones and subsequently fertilizing ovaries in a ripe cone.

Keywords: pollen, anthers, stamen About this Author James Burghardt has written for The Public Garden, Docent Educator, numerous non-profit newsletters and for Learn2Grow.com's comprehensive plant database. He holds a Master's degree in Public Horticulture from the University of Delaware and studied horticulture and biology in Australia at Murdoch University and the University of Melbourne's Burnley College. What Part of the Plant Produces Pollen? | Garden Guides What Part of the Plant Produces Pollen? What Part of the Plant Produces Pollen? Reason for flagging? Submit Overview Angiosperms are plants that reproduce sexually, by producing flowers. Flowers can be either male or female, with one flower fertilizing the other, or they may be self-pollinating, with flowers that possess both male and female organs within the same flower. Pollen is produced within the flower to provide the male portion of the reproductive process. The Male Reproductive Organ The entire male portion of the plant is referred to as the androecium. The primary parts of the androecium are the stamen and the anthers.

Some stamens are long filaments, protruding conspicuously from the center of the flower, as is the case with lily flowers. Other stamens are very short and are attached to modified leaves within the flower, as in magnolia flowers. Stamens support the anthers within the flower. Anther Structure Each anther is at the end of a stamen filament. Within the anther is sporogenic tissue that produces the actual pollen grains. Another portion of the anther is called the tapetum; it provides nutrition for the pollen that will develop within the anther. Pollen Development In the beginning of the process, pollen mothercells form. These will eventually become spores that reproduce by cell division. The tapetum will eventually enclose each spore in a cellular casing called an exine. Exines are often sticky, allowing the pollen grains to attach to pollinators such as insects. Pollen Transport After the pollen matures, it will contain the male gametophyte, or sperm cells, that are necessary for fertilization of the flower. The grains will dry out on the surface of the anther and remain there until moved by some physical force, such as wind, rain or animal interactivity.

Germination The pollen grains are then transported by this action to the stigma, the tip of the female reproductive portion of the flower. When each pollen grain contacts the stigma, it will fuse to it and release the male gametophyte, which will then move through the stigma, then into the pistil and finally into the ovary by means of a tunnel called a pollen tube. Germination then takes place. Keywords: pollen organ, pollen production, anther pollen About this Author Located in Jacksonville, Fla, Frank Whittemore has been a writer and content strategist for over 15 years, providing corporate communications services to Fortune 500 companies. Whittemore writes on topics that stem from his fascination with nature, the environment, science, medicine and technology. What Part of the Plant Produces Pollen? (with Pictures) | eHow What Part of the Plant Produces Pollen?  Email Save Pollen production is a critical part of the plant reproduction process. Pollen is produced in a male flower's stamen, and it is a powder of grains that produces the sperm seeds of plants. The stamen is the male organ of the flower and contains a small stalk called a filament.

The pollen is often spread by the wind or by insects when they land on a flower--a process called pollination. Pollen will often stick to an insect such as a honey bee, which aids in transferring the pollen to a female flower's pistil. (Ryan McVay/Photodisc/Getty Images) Pollen production is helpful for bees, which rely on pollen as a source of protein. Also, for people with allergies, pollen production and dispersal can manifest itself in the watery eyes and runny noses associated with hay fever. revetina01/iStock/Getty Images Identifying pollen is difficult without a magnifying glass because of the small size. Pollen is shaped differently depending on the type of plant from which the pollen originates. For example, the pollen produced by Entomophilous plants is a sticky, protein-rich pollen attractive to bees--it is designed to aid the pollination process. Capstoc/iStock/Getty Images There are two distinct walls in the outer layer of pollen grains. The outer wall consists of a resistant layer called the exine. The exine maintains its form while the pollen travels from one flower to the next.

The inner wall is called the intine and is made of cellulose similar to a plant cell wall. kellingo/iStock/Getty Images The location of pollen production is dependent on the type of flower producing the pollen. Pollen is produced in the anther of an angiosperm flower, the male cone of a coniferous flower or often in the male cone of other seed plants. Some plants contain both male and female reproductive cells and can self-pollinate. These are called perfect flowers. Dookfish/iStock/Getty Images Researchers are examining threats to bees and other pollinators, which could affect a plant's ability to reproduce. Scientists in some regions of the globe have noted a decrease in the number of honeybees, which could influence the numbers and diversity of plants in a region. According to a report by the North American Pollinator Protection Campaign, the estimated benefit to Americans by pollinators is approximately $14.6 billion each year. tetmc/iStock/Getty Images Flower Anatomy Printer friendly version Pollination is the first step in the process of sexual reproduction in plants. In pollination, a male pollen grain is transferred to the female part of a flower, germinates and fertilizes the ovule.

All of these steps must occur for a seed to develop. Without pollination, the production of many of the seeds and fruits that we eat would not be possible. As in all sexually reproducing organisms, mating in plants results in offspring that contain genes from both parents. Unlike animals, plants cannot seek each other out. They must rely on wind, water, or animals to move pollen between plants. Wind is responsible for pollinating many staple crops such as wheat and corn, but many Ontario crops rely heavily or completely on insects for pollination. Bees are the most commonly discussed pollinators, but many other insects and even vertebrates can play a role (see Pollinators ). Insects that visit flowers are in search of pollen and nectar . Most flowers produce nectar just to attract pollinators. The higher the concentration of sugar in the nectar, the more attractive it is to pollinators. Nectar can also contain other useful compounds such as lipids, amino acids, vitamins, and minerals. Pollen is high in protein, carbohydrate, lipids, and vitamins. It is valuable to some adult insects as a food source, and especially to bees looking for food for their young (larvae).

A nectary (nectar-producing organ)is usually positioned within the flower so that visitors to the flower have to contact the reproductive organs to access the nectar. Plants that can self-fertilize (or self-compatible) can still benefit from cross-pollination because it can lead to more or higher quality fruit. In these plants, self-pollination is often an emergency mechanism in case cross-pollination does not occur. Because plants prefer to invest their resources in cross-pollinated offspring, self-pollination often produces fewer fruit ,or fruit that is smaller or misshapen. Flower Anatomy & Function There is an incredible variety of floral shapes in nature, but they are all derived from the same basic structure. copyright Cara Dawson All plant reproduction requires that pollen be transmitted to the female organ, or pistil . (The exception is agamospermy, in which a plant produces viable seed without being fertilized.) Pollen is produced by the male organ, called the stamen . The stamen consists of an anther atop a long filament . Pollen grains released by the anther are picked up by visiting insects or the wind.

When a pollen grain reaches the female pistil (which may be on the same or a different flower), it germinates on the stigma , forming a pollen tube that grows through the style and into the ovary . The fertilized ovules then develop into seeds. Flowers may have male or female organs (called imperfect flowers), or both (referred to as perfect flowers). Examples of crops with perfect flowers include apples, cherries and legumes; crops with imperfect flowers include squash, cucumber and corn. These terms should not be confused with those that describe the plant as whole. A species may have individual plants that produce either male or female flowers (dioecious, from the Greek for 'two houses'), or plants that produce both (e.g., hermaphrodite or monoecious, 'one house'). In those species that are monoecious, individual plants may have their male and female functions in separate (imperfect) flowers, in perfect flowers, or they may have two or even all three of the flower types. Monoecious plants may also have sexual functions separated in time. This means that the pollen production and stigma receptivity to the pollen occur at different times.

All of the crops covered in this website are monoecious, but may have perfect or imperfect flowers. A perfect flower has both male and female parts (left) while imperfect flowers have either male or female parts (illustration by Cara Dawson) (a) Example of a monoecious plant species with separate male and female flowers (left) or perfect flowers (right) on the same plant. (b) Example of a dioecious species, in which male and female flowers are located on separate plants (illustration by Cara Dawson) Inbreeding (self-fertilization or fertilization by close relatives) can reduce the vigour and health of living things. An inbred plant may perform poorly and leave fewer offspring. In a crop plant, this may mean lower yields. While plants do not suffer as rapidly or severely from inbreeding as animals do, most have ways to reduce or eliminate the possibility of self-fertilization. Self-fertilization is usually only a back-up mechanism in case cross-pollination does not occur. The most effective way to ensure cross-fertilization is for plants to be dioecious, but these plants have no alternative in the event that cross pollination does not occur.

There are many different ways that plants avoid self-fertilization. These include physical separation of male and female flower parts on the plant, or staggering the fertility of male and female flowers over time. Some plants may prevent self-fertilization by chemically preventing germination of their own pollen on the stigma. Examples of perfect and imperfect flowers: a) perfect flower (legume); b) perfect flower (crab apple); c) imperfect female squash flower; d) imperfect male squash flower. Information Sheet 9, Parts of Flowers INFORMATION SHEET 9 Parts of Flowers Flowers are beautiful to us, but for the plant they serve a critical function. Flowers are how plants produce seeds to reproduce. In many cases, the flower contains male and female parts, roughly equivalent to the male and female sexes of animals. The male parts of the flower are called the stamens and are made up of the anther at the top and the stalk or filament that supports the anther. The female elements are collectively called the pistil. The top of the pistil is called the stigma, which is a sticky surface receptive to pollen. The bottom of the pistil contains the ovary and the narrowed region in between is called the style.

The male contribution or pollen is produced in the anther, and seeds develop in the ovary. Many of the fruits we eat are the thickened ovary walls surrounding the seeds. Not only does the flower contain the sexual parts necessary for reproduction, they are also like flashy roadside billboards advertising a rich supply of nectar and pollen ready and waiting for pollinating insects and other creatures. That is the bargain offered. Flowers trade rewards (in the form of sugary nectar and pollen) in return for the service that insects and other pollinators perform. Pollination is simply the transfer of pollen grains from an anther to a stigma. Fertilization occurs much later when the pollen grains germinate on the stigma and send down a pollen tube which releases the sex cells to fertilize the ovules. After fertilization, the ovules become the seeds, and the ovary wall becomes the fruit. The sexual nature of flowers and the role of the many forms, colors and scents in attracting pollinators was discovered in 1759 by Arthur Dobbs. Angiosperms. Flowering plants that have a condensed shoot tip specialized for reproduction. Anthers. The bright yellow sacs that produce and contain the pollen grains. Composites.

Flowers such as daisies, sunflowers and their relatives that are made up of lots of tiny flowers but look just like a single flower. Filament. The thin stalk that supports the anther in the male portion of the flower. Gametes. The sex cells of a flower, both male and female. The gametes are porduced within the anthers of the male part and the ovary of the female part of the flower. Gymnosperms. Plants that produce seeds without flowers, such as conifers. Nectar. A sugary liquid reward for pollinators that is produced by the nectaries. Nectaries. The tissue at the base of a flower (or elsewhere) that secrete nectar. Some plants, such as cotton, have nectaries on the leaves or stems. These are called extrafloral nectaries, and may serve to attract beneficial insects. An example is the extrafloral nectaries of peonies (a flower) that attract ants that in turn protect the unopened flower buds from caterpillars. Ovary. The base of the female portion of the flower containing the ovules which become seeds. Perfect flower.

Perfect flowers contain both the male parts and female parts within a single flower structure. Petals. The colorful, thin structures that surround the sexual parts of the flower. Not only attract pollinators, but also protect the pistil and stamen. May also produce a scent. Pollen grains. The powdery particles that contain the male sex cells (gametes). Also a nutritious, protein-rich food for bees. Pollination. The act of transferring pollen from the anther to the stigma. The pollen may be carried by the wind or water, but is usually transported by a go-between insect, bird or bat. Sepals. Commonly green, leaflike structures that protect the bud prior to opening. Stamen. Male part of flower consisting of anther and filament. Stigma. Sticky surface where the pollen lands and germinates. pollen | plant anatomy | Britannica.com plant anatomy plant reproductive system Pollen, a mass of microspores in a seed plant appearing usually as a fine dust.

Each pollen grain is a minute body, of varying shape and structure, formed in the anther, or male apparatus, in seed-bearing plants and transported by various means (wind, water, insects, etc.) to the pistil , or female structure, where fertilization occurs. The pollen grain of flowering plants (angiosperms) consists of three distinct parts. The central cytoplasmic part is the source of nuclei responsible for fertilization. The other parts constituting the wall of the grain are an inner layer, the intine , and an outer layer, the exine . The intine consists, at least in part, of cellulose . The outer and most durable layer, the exine, is very resistant to disintegration; treatment with intense heat, strong acids, or strong bases has little effect upon it. The composition of the exine is uncertain; its constituents have been termed sporopollenins. The internal parts of the pollen grain are easily broken down, whereas the exine layer, and thus the general form of the pollen grain, is easily preserved in various kinds of sediments; the quality of preservation may vary with different environments . Pollen transports sperm cells to flowers’ egg cells Encyclopædia Britannica, Inc.

Watch an Arum plant trap a fly and cover it with pollen. Contunico © ZDF Enterprises GmbH, Mainz Because of their remarkably symmetrical structure and surface patterns, pollen grains are readily recognizable under the microscope. The structure of the wall of a pollen grain is oftentimes so characteristic that in some cases species may be identified by pollen grains alone. On the other hand, there are cases in which pollen grains of very like structure occur in quite unrelated plant families. Because of their high resistance to decay, their widespread dispersal by wind and water, and their abundant production by plants, pollen grains are very common constituents of geologic sediments, both recent and ancient. Because of these features pollen grains have provided much information on the origin and geologic history of terrestrial plant life. Britannica Stories pollen - Student Encyclopedia (Ages 11 and up) A mass of microscopic spores that usually appear as a fine dust, pollen is the substance in a seed plant that causes the plant to form seeds. Each pollen grain is a minute body, of varying shape and structure. Pollen is formed in the stamen, or male apparatus, in seed-bearing plants and transported by various means to the pistil, or female structure, where fertilization occurs.

This transfer, which may take place by wind, water, insects, or other means, is called pollination. The study of pollen and spores is known as palynology. Article History Pollen Grain: Definition, Structure & Function - Video & Lesson Transcript | Study.com Pollen Grain: Definition, Structure & Function Watch short & fun videos Start Your Free Trial Today An error occurred trying to load this video. Try refreshing the page, or contact customer support. You must create an account to continue watching Register for a free trial Are you a student or a teacher? I am a student Start Your Free Trial To Continue Watching As a member, you'll also get unlimited access to over lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed. Coming up next: Flowering Plants: Reproduction & Fertilization You're on a roll. Keep up the good work! Your next lesson will play in 10 seconds 0:35 What Are Pollen Grains? 0:57 Structure of Pollen Grains 2:53 Pollination in Angiosperms Add to Add to Add to Want to watch this again later?

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Premium Edition: You can share your Custom Course by copying and pasting the course URL. Only Study.com members will be able to access the entire course. Create an account to start this course today Try it free for 5 days! Instructor: Wendy McDougal Wendy has taught high school Biology and has a master's degree in education. A pollen grain is a microscopic body that contains the male reproductive cell of a plant. It is crucial in a plant's fertilization process. Learn more about this tiny structure and take a short quiz at the end. What are Pollen Grains? Spring is a time of new growth and fresh beginnings. Days get longer, the sun gets warmer, and flowers bloom in a magnificent show of color. And as a result of these lovely blossoms everywhere, many of us find ourselves in sneezing fits. In order for flowers to propagate every year, they must be pollinated. And pollination sends millions of tiny pollen grains through the air, many of which end up in our nose. But pollen does not exist simply to make us miserable. Pollen grains represent the male portion of the reproductive process in plants and trees.

These tiny bodies are swirling in the air and on the legs of insects so that they can join the female part of the plant to create a new seed. This important process is known as fertilization. As we will discover, pollen plays a crucial role in the plant world. Structure of Pollen Grains Pollen grains are microscopic structures that vary in size and shape. Some are tiny orbs, while others are egg-shaped. Although too small to see individually, they can be seen by the naked eye in large quantities. You have probably noticed a bright orange-yellow coating on your car during springtime that closely resembles cheese powder from the macaroni and cheese box. Assorted Pollen Grains (Sunflower, Morning Glory, Hollyhock, Primrose, Castor Bean) Viewed through a microscope, a pollen grain hardly looks real. An extremely durable body, it has a tough outer coating. This hardy coat offers great protection from the harsh outdoor environment. This is important because inside this tough shell lie two cells: the tube cell, which will eventually become the pollen tube, and a generative cell, which contains the male sperm nuclei needed for fertilization. Let's zoom in to take a closer look. There are three main components of a pollen grain.

The inside of the grain is made up of cytoplasm. This fluid medium houses the aforementioned living cells, keeping them moist and alive. The outer shell is made up of two layers. The inside layer is aptly named the intine (think interior). It is composed partly of cellulose, a common component in the cell walls of plant cells. Parts of Pollen Grain The tough-as-nails outer layer is known as the exine (think exterior). This highly sophisticated and complex outer layer is rich in a compound known as sporopollenin. Waterproof, resistant to deterioration and very stiff, this shell is basically one of nature's most advanced polymers. It ensures that the tender cells inside have a strong chance of survival. In addition, often times the exine has folds, creases and spikes rising from its surface. Like extra armor, these features add to the protective nature of this layer. They also play an important role in the mobility of the grains, making it more likely that they will stick to the legs of insects as well as catch the wind. Pollination in Angiosperms Pollen is produced and transported in slightly different ways depending on whether the plant is an angiosperm or a gymnosperm.

Angiosperms are flowering plants, and gymnosperms are non-flowering. Let's first take a look at pollen in angiosperms. In angiosperms, pollen is produced by the anther, which sits on the filament in the center of the flower. Look closely and you will most certainly see the fine yellow powder on each anther. Pollen on Anthers of a Flower In order to complete fertilization, pollen must make its way to another plant. Since pollen cannot move on its own, it must rely on other methods of transport. × The Structure and Functions of Flowers The Structure and Functions of Flowers The Female Reproductive Organ: The Carpel The female parts of a flower consist of an ovary, which contains one or more ovules, a style and the stigma. The ovary is at the base of the flower. From the ovary, extends a tubular structure called the style and on the top of the style is a surface receptive to pollen called the stigma. The stigma can take many different forms, most of them designed to help trap pollen. There are many variations on this basic structural theme. After fertilization the ovule becomes the seed and the ovary becomes the fruit.

The Male Reproductive Organ: The Stamen The male parts of a flower consist of one or more stamens. Each stamen is made up of paired anthers (sacs containing pollen) on a filament or stalk. The anthers are the orange/yellow structures often seen in the centre of a flower. Pollen from the anthers of one flower is transferred to the stigma of another usually either by wind, or by animals, especially insects. PETALS, COROLLA, SEPALS, CALYX The reproductive structures in higher plants are contained within flowers. Flowers have more than one petal, and the flower petals are collectively called the corolla. A flower bud is protected by green leafy structures called sepals. Collectively, all of the sepals form the calyx. The corolla or petals are often brightly coloured with markings attractive to insects. The flowers may also be scented. For instance, Honeysuckle has showy, attractive flowers which attract insects by day. However, in the dark, their colourful show is not much use, and their heady scent then helps to attract night-flying moths.

In insect-pollinated plants, there are also usually nectaries which secrete sugary nectar, located within the flower. These provide an incentive to insects to visit the flowers. In the search for nectar, the insects will often get pollen grains caught on their bodies. This may then brush off onto the stigma of the next flower visited and in this way the flowers are pollinated. The receptacle is the place on the stem where floral organs originate and attach.ï¿½ï¿½ï¿½ï¿½ Formation of Sex Cells The sex cells of the flowering plant are called gametes. There are both male and female gametes thus the flower undergoes sexual reproduction. Male Gametes Pollen Formation: Development Of A Pollen Grain Within The Pollen Sac Of An Anther:ï¿½ï¿½ï¿½ï¿½ A cross section of the developing anther displays four chambers. These chambers are called pollen sacs (see upper illustration). Each pollen sac is filled with cells containing large nuclei. As the anther grows, each of these cells goes through two meiotic divisions, forming a tetrad. These cells are called microspores. Each one of these microspores eventually becomes a pollen grain.

Each pollen sac is enclosed by a protective epidermis and a fibrous layer. Inside the fibrous layer is the tapetum. This is a food store and will provide energy for future cell divisions. Each pollen grain is surrounded by a tough protective wall called an exine. This is a tough covering that allows the pollen grain to survive harsh conditions for long periods of time. The intine is another thin protective coating. First, each nucleus divides by mitosis to become two nuclei. One is the tube nucleus. The other is a generative nucleus.ï¿½ The wall of the cell thickens to protect the developing pollen grain. As the anther ripens, the wall between the paired pollen sacs disappears. The pollen sacs burst open and the mature pollen grains are ready for dispersal. Development of the Embryo Sac Each ovary contains one or more ovules. The green structure at the top of the diagram is the ovule. The integuments are the 2 walls of the ovule. There is a small opening in the walls called a micropyle. This is where the pollen tube will enter. (Will be discussed later.) The nucellus is cells that provide nutrition for the growth of the ovule.

The embryo sac, also known as the megaspore, divides by meiosis to form 4 haploid cells. Three of these cells degenerate and one remains. Only one megaspore survives in each ovule. This becomes the embryo sac. The haploid nucleus of the surviving megaspore undergoes three mitotic divisions. Eight haploid nuclei are now present. Within the swollen ï¿½megaspore cellï¿½ six haploid cells and two ï¿½polar nucleiï¿½ are formed. The entire structure is called the embryo sac. One of the cells near to the micropyle end of the ovule is the haploid female gamete (egg cell). ï¿½ï¿½ï¿½ï¿½ï¿½ The Carpel With a Mature Embryo Sac will appear as shown below: Pollination Pollination is the transfer of pollen (male gamete) from the anther to a stigma. Cross-pollination: pollen is transferred to the stigma of another plant.

Increases genetic variation, population more resistant to environmental change.ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Self-pollination: pollen transferred to the stigma of the same flower or a flower of the same plant. Guarantees reproduction if pollinating agent is absent or not efficient. Pollination can be accomplished by the wind or by animals. Insects are the most common animals that will pollinate a carpel. The most sophisticated relationships between plants and insects are generally those involving bees. Bees collect pollen and nectar not only for themselves but also to feed their young. For this reason bees have developed a number of adaptations that make them particularly good pollen carriers. Bees have special hairs that are arranged to form pollen 'baskets' on their hindlegs and the underside of their abdomen. These adaptations allow them to gather and carry large volumes of pollen. Bees are ideal pollinators because they visit many flowers while carrying lots of pollen, before returning to their nest.

So the chance that a bee will transfer the pollen between flowers of the same species is very high. Many insects eat pollen. In the process of eating they become covered in it. Pollination happens when the pollen feeder transfers the pollen to the pollen receivers of the same plant, or another plant of the same species, as the insect looks for more pollen to eat. Fertilisation ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Fertilisation is the union of the male and female gametes to form a zygote. Since the male and female gametes are haploid (n) when the two unite the zygote is diploid (2n). Fertilisation starts when a pollen grain lands on the stigma. The pollen grain then grain germinates forming a pollen tube. The tube nucleus controls the growth of the pollen tube. The pollen tube is an example of chemotropism since it is growing toward chemicals produced from the ovule. The generative nucleus travels down the pollen tube. It undergoes mitosis forming two haploid male gamete nuclei.

The pollen tube enters the ovule by way of the micropyle. The two male gamete nuclei are released into the embryo sac. The tube nucleus disintegrates. Double Fertilisation ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Since there are 2 sperm nuclei that have reached the embryo sac both nuclei will fuse with female gametes. One sperm nuclei will fuse with the egg cell to form the zygote (2n) while the other sperm nucleus fuses with the 2 polar nuclei in the embryo sac to form an endosperm nucleus (3n). Click here to view an animation of double fertilisation Seed Formation The fertilized becomes the seed. The integuments become the wall of the seed called the testa. The micropyle closes. The endosperm nucleus leads to the formation of triploid endosperm, a food tissue. The diploid zygote, by mitosis, develops into a plant embryo. The developing embryo draws nourishment from the endosperm. The embryo ceases development and goes dormant.

The ovule becomes a seed, which contains a dormant plant embryo, food reserve, and the protective coat called the testa. The Embryo ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ The embryo is made up of the radicle or future root and the plumule or future shoot. The endosperm cells divide many times and absorb the nucellus. This is the nutrition (mainly fats, oils and starch) for the embryo. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ There are 2 types of seeds. Some are endospermic while others are non-endospermic.ï¿½ In endospermic seeds the food reserve is the endosperm, which is outside the plant embryo. Examples of this type of seed are maize and wheat. Non-endospermic seeds have food reserve within the cotyledon(s) of the plant embryo. This occurs in broad beans.

Monocots and Dicots ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Monocots have one cotyledon in the seed while dicots have two cotyledons. The cotyledons are food reserves for the young plant after it germinates from the soil. It uses these food reserves until it is capable of making its own food. In monocots the food is absorbed from the endosperm while in dicots the food is stored in the cotyledons.

Monocotï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Dicot Fruit Development The ovary becomes a fruit. The wall of the ovary becomes the wall of the fruit called the pericarp. The fruit protects the developing seeds and plays an important role in seed dispersal. This process is controlled by auxins produced by the seeds. Once the fruit forms the rest of the flower parts die and fall away. Fruit and Seed Dispersal Seed dispersal is the scattering of offspring away from each other and from the parent plant.

As a result of dispersal there is an improved chance of success by reducing competition and overcrowding. Dispersal also enables colonisation of new suitable habitatsï¿½ and thus, there is an increased chance of species survival. Methods of Seed Dispersal Wind: The seeds of wind-dispersed plants are lightweight seeds. They have a high air resistance so they can be carried far away from the mother plant. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ ï¿½ï¿½ï¿½ï¿½ï¿½ Water Dispersal Fruits which float such as those of the water lily and the coconut palm are carried by water. Coconuts can travel for thousands of kilometres across seas and oceans. The original coconut palms on South Sea Islands grew from fruits, which were carried there from the mainland by ocean currents. Mangroves in the swamp regions of countries such as Thailand are another example. Some plants have juicy fruit that animals like to eat. The animal eats the fruit but only the juicy part is digested.

The stones and pips pass through the animal's digestive system and are excreted to form new plants. This can be far away from the parent plant. Blackberry, cherry and apple seeds are dispersed in this way. Birds also like to eat fruit and they help to disperse seeds to other areas through their droppings. Mistletoe has sticky fruits that are attractive to birds. The sticky seeds stick to the bird's beak. They then rub their beaks clean on the bark of trees. The sticky seeds are left on the bark to grow into new mistletoe plants - mistletoe is a parasitic plant. Squirrels collect nuts like acorns and bury them for winter food, but they often forget where they have buried them and these grow into new trees. Some fruits like that of the burdock plant have seeds with hooks. These catch on the fur of animals and are carried away. Self-Dispersal: Some plants have pods that explode when ripe and shoot out the seeds. Lupins, gorse and broom scatter their seeds in this way. Pea and bean plants also keep their seeds in a pod.

When the seeds are ripe and the pod has dried, the pod bursts open and the peas and beans are scattered. Dormancy ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Dormancy is a period of inactivity. There is very little cellular activity and no growth. One or many of the following reasons bring about dormancy: Auxins that inhibit growth- Growth Inhibitors The testa is impermeable to water and oxygen- The testa will eventually break down and allow water and oxygen into the seed. The testa may be too hard for the embryo to germinate. An Auxin (Growth Regulator) may be absent until suitable environmental conditions develop. Germination ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ The embryo will germinate from the seed if the proper environmental conditions are present. When this occurs the embryo resumes its growth. In order for germination to occur the following conditions must be present: Water must be present. This allows the seed to swell and enzymes to function. Oxygen must be present in the soil. The temperature must be suitable for the species of plant.

Suitable temperatures are usually between 5-30 degrees Celsius depending on the species. The dormancy period must be complete. Some seeds need light and others need darkness. Events of Germination ï¿½ï¿½ï¿½ When germination begins the first thing that happens is water is absorbed by the seed through the micropyle and through the testa. Enzymes in the soil now digest the foods stored in the seeds: ï¿½ Oils become fatty acids and glycerol ï¿½ Starch becomes glucose ï¿½ Protein becomes amino acids ï¿½ These foods now are absorbed by the embryo. ï¿½ The glucose and amino acids make new structures such as cell walls and enzymes.ï¿½ ï¿½ The fats and glucose are used in cellular respiration to produce energy. ï¿½ The stored food of the seed is being used up as the embryo grows larger. ï¿½ The radicle grows larger and breaks through the testa. It becomes the roots of the new plant. ï¿½ The plumule grows larger and emerges above the ground. ï¿½ Leaves form.

ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Germination occurs differently in different plants. In some plants the cotyledon remains underground while in other plants the cotyledon emerges above ground. The diagrams below show these 2 methods of germination. Click here to see an animation of:

Question: Which part of a flower is responsible for the production of pollen grains?
Answer: Anther