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Pollination is one of the most fascinating processes in our nature. Pollination is how flowering plants reproduce. To produce offspring, a plant needs to be fertilised, which allows it to develop seeds that will grow into new plants.
Flowers have both male and female parts. The male part is called stamen and is a long slender stalk with pollens at the end. Pollens are small, powdery substance that are normally yellowish in colour. The female part is called stigma and sits normally at the centre of the flower. During pollination, the pollens from the stamen, the male part are transferred to the stigma, the female part. Through this fertilization, fruits and seeds are developed.
Flowers need external agents to move pollens from the male parts to female parts. Normally, pollen are transferred by wind, water, birds, bees, butterflies, bats, and other animals that visit flowers. We call animals or insects that transfer pollen from male organ to female organ “pollinators”.
When a mature plant is ready to reproduce, its buds swell and open into flowers. A pollinator visits a flower to eat nectar and pollen. The pollen grains from the flower will rub onto the pollinator and stick to its body. As the pollinator moves from flower to flower, its body collects more pollen. As the pollinator continues to visit more flowers, its body is rubbed off against the female part of the flower, and pollen is deposited on the stigma facilitating fertilization to occur.
There are approximately 350,000 species of known pollinators (bees, flies, butterflies, moths, wasps, beetles, birds, and bats) serving approximately 352,000 species of flowering plants. The vast majority of pollinator species are wild while some species such as honeybees are managed by humans.
Let’s look at some of the most common pollinators:
Bees: Bees are the most well known pollinators. Bees collect pollen and nectar not only for themselves but also to feed their young larvae. For this reason bees have developed a number of adaptive features that make them particularly good pollen carriers. Bees are fuzzy and carry an electrostatic charge. Both features help pollen grains attach to their bodies, but they also have specialized pollen-carrying structures. They have special hairs that are arranged to form “pollen baskets' on their hind legs and the underside of their abdomen. Bees are not picky and frequently visit a large variety of flowers. These adaptive characters allow bees to gather and carry large volumes of pollen and make them one of the most successful pollinators.
We are benefiting from the hard work of bees, when we are eating foods such as apples, grapes, pears, peaches, almonds, pumpkins, watermelons, cabbage, cauliflower, coffee, berries, mustard, onions and potatoes. Seventy out of the top 100 human food crops are pollinated by both domesticated and wild bees.
Butterflies: Butterflies like to sit on larger flower heads when they hunt nectar, collecting pollen on their legs and body as they search for food. The legs and the butterfly's proboscis are longer and farther away from the flower's pollen so less pollen collects on its body parts than it does on bees, but still they are very effective pollinators. Butterflies pollinate vegetables and herbs such as carrots, peas, beans, fennel and cilantro.
Flies: Flies are primary pollinators for many plant species such as pears, apples, strawberries, cherries, plums, apricots, peaches, rowanberries, raspberries, blackberries, roses, mangoes, fennel, coriander, caraway, kitchen onions, parsley, and carrots. Without flies, there would be no chocolate. Chocolate midge flies pollinate cacao trees native to Central America, South America, Africa, and Asia. The tiny insects are about one to three millimetres long, allowing them to fit inside the plant's small flowers.
Compared to bees, which need to collect nectar not only for themselves but also their hives, adult flies have low requirements. Although this makes flies less devoted to the task of moving quickly between flowers, it also frees them to bask in flowers and remain active at low temperatures.
Some plant’s flowers have adapted putrid smelling blossoms to attract certain fly pollinators looking for rotting meat. Some flowers have even adapted to look like rotting meat, usually having a brownish red color.
Bats: Bats are very important pollinators in tropical and desert climates. They feed on the insects in the flowers as well as on the nectar and flower parts. Over 300 species of fruit depend on bats for pollination. Over 300 species of fruit depend on bats for pollination. These fruits include: mangoes, bananas, guavas, durian and dragonfruits. Bats are attracted to dull white, green or purple flowers that emit strong, musty odors at night.
Hummingbirds: Because hummingbirds feed frequently and have a long needle like beak, they are ideal pollinators for many flowers. Hummingbirds have long, slender bills (beak) and tube-like tongues that they use to drink nectar from brightly-colored flowers. Hummingbirds are attracted to scarlet, orange, red or white tubular-shaped flowers with no distinct odors.
Sunbirds: Sunbird species can drink nectar while hovering, but usually perch to feed. Their long curved beaks and long, brush-tipped tongues make these birds particularly suited to feeding on and pollinating tubular flowers.
Sunbirds play a major role in pollinating rhododendrons, common species of the Himalayas.
Plants and pollinators evolved together side by side over millions of years. Plants developed many complex ways of attracting pollinators. The great variety in color, form, and scent we see in flowers is a direct result of the intimate relationship of flowers with pollinators. Similarly, pollinators evolved with specialized physical traits and behaviors that enhance their pollination efforts. These methods include visual cues, scent, food, mimicry, and entrapment.
Likewise, many pollinators have evolved specialized structures and behaviors to assist in plant pollination such as the fur on the face of the black and white ruffed lemur or a bat. Animal pollinated flowering plants produce pollen that is sticky and barbed to attach to the animal and thus be transferred to the next flower.
[Plants don’t always need pollination for reproduction. There are many plants (around 6% of total plant species) that reproduce asexually. This method does not require the plants to produce a flower, attract pollinators, or find a means of seed dispersal. ]