In some species, the pollen and the ovary mature at different times. These flowers make self-pollination nearly impossible. By the time pollen matures and has been shed, the stigma of this flower is mature and can only be pollinated by pollen from another flower.
Some flowers have developed physical features that prevent self-pollination. The primrose employs this technique. Primroses have evolved two flower types with differences in anther and stigma length: the pin-eyed flower and the thrum-eyed flower. This allows insects to easily cross-pollinate while seeking nectar at the pollen tube. This phenomenon is also known as heterostyly.
Many plants, such as cucumbers, have male and female flowers located on different parts of the plant, thus making self-pollination difficult. In other species, the male and female flowers are borne on different plants, making them dioecious. All of these are barriers to self-pollination; therefore, the plants depend on pollinators to transfer pollen. The majority of pollinators are biotic agents such as insects bees, flies, and butterflies , bats, birds, and other animals.
Other plant species are pollinated by abiotic agents, such as wind and water. Pollinators : To maximize their avoidance of self-pollination, plants have evolved relationships with animals, such as bees, to ensure cross-pollination between members of the same species. Plants have developed adaptations to promote symbiotic relationships with insects that ensure their pollination. Bees are perhaps the most important pollinator of many garden plants and most commercial fruit trees. The most common species of bees are bumblebees and honeybees.
Since bees cannot see the color red, bee-pollinated flowers usually have shades of blue, yellow, or other colors. Bees collect energy -rich pollen or nectar for their survival and energy needs. They visit flowers that are open during the day, are brightly colored, have a strong aroma or scent, and have a tubular shape, typically with the presence of a nectar guide.
A nectar guide includes regions on the flower petals that are visible only to bees, which help guide bees to the center of the flower, thus making the pollination process more efficient. Recently, there have been many reports about the declining population of honeybees. 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. When a pollen grain comes into contact with the stigma, or top of the pistil, it sends a pollen tube down into the ovary at the pistil's base.
As the pollen tube penetrates the ovule, it releases two sperm cells. One fuses with the egg to create a diploid zygote, while the other joins with the fusion nucleus to form a triploid nucleus. This triploid nucleus turns into an endosperm, which nourishes the developing embryo filling the role of gametophyte tissue in the gymnosperm seed. As in gymnosperms, the ovule becomes a seed, encasing the embryo and endosperm in a seed coat.
But unlike gymnosperms, in angiosperms the ovary containing the ovules develops into a fruit after fertilization. The fruit gives the embryos the double benefit of added protection against desiccation and increased dispersal, since it is eaten by far-ranging animals who then excrete the seeds.
In a population, this genetic variation is important because, if conditions become hard, there is a chance that some individuals will survive. Many flowering plants are also able to reproduce asexually through various structures such as stolons, rhizomes and tubers.
However, all individuals produced like this are clones of their parent, with no genetic variation. This means that, if something happens that is fatal to one individual, such as a disease outbreak, it is likely to be fatal to all. Pollination is a very important part of the life cycle of a flowering plant. It is part of the sexual reproduction process of flowering plants, which results in seeds that will grow into new plants. Flowers are the structures of flowering plants that contain all the specialised parts needed for sexual reproduction.
Plants have gametes, which contain half the normal number of chromosomes for that plant species. Male gametes are found inside tiny pollen grains on the anthers of flowers. Female gametes are found in the ovules of a flower. The ovary surrounding the ovules develops into a fruit that contains one or more seeds.
After fertilization the flower withers. The sepals and the petals dry up, the ovary converts into fruit, the ovule forms the seed and the zygote forms the embryo which is enclosed in the seed. Plants need mineral elements to become fertilized. The major mineral elements that they need are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, magnesium and sulphur. The most generalized form of this process requires four steps: pollination, germination, penetration of the ovule, and fertilization.
Plants that reproduce by seeds. Seed plants have special structures on them where male and female cells join together through a process called fertilisation. The parent plant disperses or releases the seed. If the seed lands where the conditions are right, the embryo germinates and grows into a new plant. The ovule is the organ that forms the seeds of flowering plants. For example, Piper, Polygonum, Cycas. Anatropous ovules are the ovules that are completely inverted on its stalk.
For example, Helianthus and Tridax.
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