What is pollination how does it differ from fertilization

Many flowers will remain unpollinated, failing to bear seeds if honeybees disappear. The impact on commercial fruit growers could be devastating. Pollination by insects : Insects, such as bees, are important agents of pollination.

Bees are probably the most important species of pollinators for commercial and garden plant species. Many flies are attracted to flowers that have a decaying smell or an odor of rotting flesh.

These flowers, which produce nectar, usually have dull colors, such as brown or purple. They are found on the corpse flower or voodoo lily Amorphophallus , dragon arum Dracunculus , and carrion flower Stapleia, Rafflesia. The nectar provides energy while the pollen provides protein. Wasps are also important insect pollinators, pollinating many species of figs.

Butterflies, such as the monarch, pollinate many garden flowers and wildflowers, which are usually found in clusters. These flowers are brightly colored, have a strong fragrance, are open during the day, and have nectar guides.

Moths, on the other hand, pollinate flowers during the late afternoon and night. The flowers pollinated by moths are pale or white and are flat, enabling the moths to land. One well-studied example of a moth-pollinated plant is the yucca plant, which is pollinated by the yucca moth.

The shape of the flower and moth have adapted in a way to allow successful pollination. The moth deposits pollen on the sticky stigma for fertilization to occur later. The female moth also deposits eggs into the ovary. As the eggs develop into larvae, they obtain food from the flower and developing seeds. Thus, both the insect and flower benefit from each other in this symbiotic relationship. The corn earworm moth and Gaura plant have a similar relationship.

Moths as pollinators : A corn earworm a moth sips nectar from a night-blooming Gaura plant. Both the moth and plant benefit from each other as they have formed a symbiotic relationship; the plant is pollinated while the moth is able to obtain food. Plants have developed specialized adaptations to take advantage of non-insect forms of pollination. These methods include pollination by bats, birds, wind, and water. In the tropics and deserts, bats are often the pollinators of nocturnal flowers such as agave, guava, and morning glory.

The flowers are usually large and white or pale-colored so that they can be distinguished from their dark surroundings at night. The flowers have a strong, fruity, or musky fragrance and produce large amounts of nectar. They are naturally-large and wide-mouthed to accommodate the head of the bat. As the bats seek the nectar, their faces and heads become covered with pollen, which is then transferred to the next flower.

Many species of small birds, such as hummingbirds and sun birds, are pollinators for plants such as orchids and other wildflowers. Flowers visited by birds are usually sturdy and are oriented in a way to allow the birds to stay near the flower without getting their wings entangled in the nearby flowers.

Brightly-colored, odorless flowers that are open during the day are pollinated by birds. Botanists determine the range of extinct plants by collecting and identifying pollen from year-old bird specimens from the same site. Pollination by birds : Hummingbirds have adaptations that allow them to reach the nectar of certain tubular flowers, thereby, aiding them in the process of pollination.

Most species of conifers and many angiosperms, such as grasses, maples, and oaks, are pollinated by wind.

Pine cones are brown and unscented, while the flowers of wind-pollinated angiosperm species are usually green, small, may have small or no petals, and produce large amounts of pollen. Unlike the typical insect-pollinated flowers, flowers adapted to pollination by wind do not produce nectar or scent.

In wind-pollinated species, the microsporangia hang out of the flower, and, as the wind blows, the lightweight pollen is carried with it. The flowers usually emerge early in the spring before the leaves so that the leaves do not block the movement of the wind. The pollen is deposited on the exposed feathery stigma of the flower. Wind pollination : These male a and female b catkins from the goat willow tree Salix caprea have structures that are light and feathery to better disperse and catch the wind-blown pollen.

Some weeds, such as Australian sea grass and pond weeds, are pollinated by water. The pollen floats on water. When it comes into contact with the flower, it is deposited inside the flower. Orchids are highly-valued flowers, with many rare varieties. They grow in a range of specific habitats, mainly in the tropics of Asia, South America, and Central America.

At least 25, species of orchids have been identified. Flowers often attract pollinators with food rewards, in the form of nectar. However, some species of orchid are an exception to this standard; they have evolved different ways to attract the desired pollinators. They use a method known as food deception, in which bright colors and perfumes are offered, but no food. Anacamptis morio , commonly known as the green-winged orchid, bears bright purple flowers and emits a strong scent.

The bumblebee, its main pollinator, is attracted to the flower because of the strong scent, which usually indicates food for a bee.

In the process, the bee picks up the pollen to be transported to another flower. Other orchids use sexual deception. Chiloglottis trapeziformis emits a compound that smells the same as the pheromone emitted by a female wasp to attract male wasps. The male wasp is attracted to the scent, lands on the orchid flower, and, in the process, transfers pollen. Some orchids, like the Australian hammer orchid, use scent as well as visual trickery in yet another sexual deception strategy to attract wasps.

The flower of this orchid mimics the appearance of a female wasp and emits a pheromone. The male wasp tries to mate with what appears to be a female wasp, but instead picks up pollen, which it then transfers to the next counterfeit mate. Pollination by deception in orchids : Certain orchids use food deception or sexual deception to attract pollinators. Shown here is a bee orchid Ophrys apifera. After pollen is deposited on the stigma, it must germinate and grow through the style to reach the ovule.

The microspores, or the pollen, contain two cells: the pollen tube cell and the generative cell. The pollen tube cell grows into a pollen tube through which the generative cell travels. The germination of the pollen tube requires water, oxygen, and certain chemical signals. During this process, if the generative cell has not already split into two cells, it now divides to form two sperm cells.

The pollen tube is guided by the chemicals secreted by the synergids present in the embryo sac; it enters the ovule sac through the micropyle. Of the two sperm cells, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid cell that develops into the endosperm.

Together, these two fertilization events in angiosperms are known as double fertilization. After fertilization is complete, no other sperm can enter. The fertilized ovule forms the seed, whereas the tissues of the ovary become the fruit, usually enveloping the seed.

Double fertilization : In angiosperms, one sperm fertilizes the egg to form the 2n zygote, while the other sperm fuses with two polar nuclei to form the 3n endosperm. This is called a double fertilization. After fertilization, embryonic development begins.

The zygote divides to form two cells: the upper cell terminal cell and the lower cell basal cell. The division of the basal cell gives rise to the suspensor, which eventually makes connection with the maternal tissue. The suspensor provides a route for nutrition to be transported from the mother plant to the growing embryo. The terminal cell also divides, giving rise to a globular-shaped proembryo. In dicots eudicots , the developing embryo has a heart shape due to the presence of the two rudimentary cotyledons.

In non-endospermic dicots, such as Capsella bursa , the endosperm develops initially, but is then digested. In this case, the food reserves are moved into the two cotyledons.

As the embryo and cotyledons enlarge, they become crowded inside the developing seed and are forced to bend. Ultimately, the embryo and cotyledons fill the seed, at which point, the seed is ready for dispersal. Embryonic development is suspended after some time; growth resumes only when the seed germinates. The developing seedling will rely on the food reserves stored in the cotyledons until the first set of leaves begin photosynthesis. After fertilization, the zygote divides to form an upper terminal cell and a lower basal cell.

The basal cell also divides, giving rise to the suspensor. Monocot and dicot seeds develop in differing ways, but both contain seeds with a seed coat, cotyledons, endosperm, and a single embryo. The seed, along with the ovule, is protected by a seed coat that is formed from the integuments of the ovule sac. In dicots, the seed coat is further divided into an outer coat, known as the testa, and inner coat, known as the tegmen. The embryonic axis consists of three parts: the plumule, the radicle, and the hypocotyl.

The portion of the embryo between the cotyledon attachment point and the radicle is known as the hypocotyl. The embryonic axis terminates in a radicle, which is the region from which the root will develop. In angiosperms, the process of seed development begins with double fertilization and involves the fusion of the egg and sperm nuclei into a zygote.

Flowers visited by birds are usually sturdy and are oriented in such a way as to allow the birds to stay near the flower without getting their wings entangled in the nearby flowers. Brightly colored, odorless flowers that are open during the day are pollinated by birds. Botanists have been known to determine the range of extinct plants by collecting and identifying pollen from year-old bird specimens from the same site.

Most species of conifers, and many angiosperms, such as grasses, maples and oaks, are pollinated by wind. Pine cones are brown and unscented, while the flowers of wind-pollinated angiosperm species are usually green, small, may have small or no petals, and produce large amounts of pollen.

Unlike the typical insect-pollinated flowers, flowers adapted to pollination by wind do not produce nectar or scent. In wind-pollinated species, the microsporangia hang out of the flower, and, as the wind blows, the lightweight pollen is carried with it Figure. The flowers usually emerge early in the spring, before the leaves, so that the leaves do not block the movement of the wind.

The pollen is deposited on the exposed feathery stigma of the flower Figure. Some weeds, such as Australian sea grass and pond weeds, are pollinated by water. The pollen floats on water, and when it comes into contact with the flower, it is deposited inside the flower. Pollination by Deception Orchids are highly valued flowers, with many rare varieties Figure. They grow in a range of specific habitats, mainly in the tropics of Asia, South America, and Central America.

At least 25, species of orchids have been identified. Flowers often attract pollinators with food rewards, in the form of nectar. However, some species of orchid are an exception to this standard: they have evolved different ways to attract the desired pollinators. They use a method known as food deception, in which bright colors and perfumes are offered, but no food. Anacamptis morio , commonly known as the green-winged orchid, bears bright purple flowers and emits a strong scent.

The bumblebee, its main pollinator, is attracted to the flower because of the strong scent—which usually indicates food for a bee—and in the process, picks up the pollen to be transported to another flower. Other orchids use sexual deception. Chiloglottis trapeziformis emits a compound that smells the same as the pheromone emitted by a female wasp to attract male wasps.

The male wasp is attracted to the scent, lands on the orchid flower, and in the process, transfers pollen. Some orchids, like the Australian hammer orchid, use scent as well as visual trickery in yet another sexual deception strategy to attract wasps. The flower of this orchid mimics the appearance of a female wasp and emits a pheromone.

The male wasp tries to mate with what appears to be a female wasp, and in the process, picks up pollen, which it then transfers to the next counterfeit mate. After pollen is deposited on the stigma, it must germinate and grow through the style to reach the ovule.

The microspores, or the pollen, contain two cells: the pollen tube cell and the generative cell. The pollen tube cell grows into a pollen tube through which the generative cell travels.

The germination of the pollen tube requires water, oxygen, and certain chemical signals. In the meantime, if the generative cell has not already split into two cells, it now divides to form two sperm cells.

The pollen tube is guided by the chemicals secreted by the synergids present in the embryo sac, and it enters the ovule sac through the micropyle. Of the two sperm cells, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid cell that develops into the endosperm. Together, these two fertilization events in angiosperms are known as double fertilization Figure.

After fertilization is complete, no other sperm can enter. The fertilized ovule forms the seed, whereas the tissues of the ovary become the fruit, usually enveloping the seed. After fertilization, the zygote divides to form two cells: the upper cell, or terminal cell, and the lower, or basal, cell. The division of the basal cell gives rise to the suspensor , which eventually makes connection with the maternal tissue.

The suspensor provides a route for nutrition to be transported from the mother plant to the growing embryo. The terminal cell also divides, giving rise to a globular-shaped proembryo Figure a. In dicots eudicots , the developing embryo has a heart shape, due to the presence of the two rudimentary cotyledons Figure b. In non-endospermic dicots, such as Capsella bursa , the endosperm develops initially, but is then digested, and the food reserves are moved into the two cotyledons.

As the embryo and cotyledons enlarge, they run out of room inside the developing seed, and are forced to bend Figure c. Ultimately, the embryo and cotyledons fill the seed Figure d , and the seed is ready for dispersal.

Embryonic development is suspended after some time, and growth is resumed only when the seed germinates. The developing seedling will rely on the food reserves stored in the cotyledons until the first set of leaves begin photosynthesis. The mature ovule develops into the seed. A typical seed contains a seed coat, cotyledons, endosperm, and a single embryo Figure. In monocots, such as corn and wheat, the single cotyledon is called a scutellum ; the scutellum is connected directly to the embryo via vascular tissue xylem and phloem.

Food reserves are stored in the large endosperm. Upon germination, enzymes are secreted by the aleurone , a single layer of cells just inside the seed coat that surrounds the endosperm and embryo.

The enzymes degrade the stored carbohydrates, proteins and lipids, the products of which are absorbed by the scutellum and transported via a vasculature strand to the developing embryo. Therefore, the scutellum can be seen to be an absorptive organ, not a storage organ. The two cotyledons in the dicot seed also have vascular connections to the embryo. In endospermic dicots , the food reserves are stored in the endosperm. During germination, the two cotyledons therefore act as absorptive organs to take up the enzymatically released food reserves, much like in monocots monocots, by definition, also have endospermic seeds.

Tobacco Nicotiana tabaccum , tomato Solanum lycopersicum , and pepper Capsicum annuum are examples of endospermic dicots. In non-endospermic dicots , the triploid endosperm develops normally following double fertilization, but the endosperm food reserves are quickly remobilized and moved into the developing cotyledon for storage.

The two halves of a peanut seed Arachis hypogaea and the split peas Pisum sativum of split pea soup are individual cotyledons loaded with food reserves. The seed, along with the ovule, is protected by a seed coat that is formed from the integuments of the ovule sac. In dicots, the seed coat is further divided into an outer coat known as the testa and inner coat known as the tegmen.

The embryonic axis consists of three parts: the plumule, the radicle, and the hypocotyl. The embryonic axis terminates in a radicle the embryonic root , which is the region from which the root will develop.

In dicots, the hypocotyls extend above ground, giving rise to the stem of the plant. In monocots, the hypocotyl does not show above ground because monocots do not exhibit stem elongation. The part of the embryonic axis that projects above the cotyledons is known as the epicotyl. The plumule is composed of the epicotyl, young leaves, and the shoot apical meristem.

Upon germination in dicot seeds, the epicotyl is shaped like a hook with the plumule pointing downwards. This shape is called the plumule hook, and it persists as long as germination proceeds in the dark. Therefore, as the epicotyl pushes through the tough and abrasive soil, the plumule is protected from damage. Upon exposure to light, the hypocotyl hook straightens out, the young foliage leaves face the sun and expand, and the epicotyl continues to elongate.

During this time, the radicle is also growing and producing the primary root. As it grows downward to form the tap root, lateral roots branch off to all sides, producing the typical dicot tap root system. In monocot seeds Figure , the testa and tegmen of the seed coat are fused. As the seed germinates, the primary root emerges, protected by the root-tip covering: the coleorhiza. Next, the primary shoot emerges, protected by the coleoptile : the covering of the shoot tip. Upon exposure to light i.

At the other end of the embryonic axis, the primary root soon dies, while other, adventitious roots roots that do not arise from the usual place — i.

This gives the monocot a fibrous root system. Many mature seeds enter a period of inactivity, or extremely low metabolic activity: a process known as dormancy , which may last for months, years, or even centuries. Dormancy helps keep seeds viable during unfavorable conditions. Upon a return to favorable conditions, seed germination takes place. Favorable conditions could be as diverse as moisture, light, cold, fire, or chemical treatments.

After heavy rains, many new seedlings emerge. Forest fires also lead to the emergence of new seedlings. Some seeds require vernalization cold treatment before they can germinate. This guarantees that seeds produced by plants in temperate climates will not germinate until the spring.

Plants growing in hot climates may have seeds that need a heat treatment in order to germinate, to avoid germination in the hot, dry summers. In many seeds, the presence of a thick seed coat retards the ability to germinate. Scarification , which includes mechanical or chemical processes to soften the seed coat, is often employed before germination. Depending on seed size, the time taken for a seedling to emerge may vary. Species with large seeds have enough food reserves to germinate deep below ground, and still extend their epicotyl all the way to the soil surface.

Seeds of small-seeded species usually require light as a germination cue. It is an internal mechanism and takes place inside the flowers. It occurs in Pollination occurs in flowering plants only Fertilization is followed by almost every plant and living being present on earth.

Type Two types:Self-pollination.