Biology AGENTS OF POLLINATION

KEY TOPICS

`star` Pollination by Wind
`star` Pollination by Water
`star` Pollination by Animals

POLLINATION BY WIND

● Pollination by wind is more common amongst `color{Violet}"abiotic pollinations"`.

● Wind pollination also requires that the pollen grains are `color{Violet}"light and non-sticky"` so that they can be transported in `color{Violet}"wind currents"`.

● They often possess `color{Violet}"well-exposed stamens"` (so that the pollens are easily dispersed into wind currents, and large often-`color{Violet}"feathery stigma"` to easily trap air-borne pollen grains.

● Wind pollinated flowers often have a `color{Violet}"single ovule"` in each ovary and `color{Violet}"numerous flowers"` packed into an inflorescence.

● A familiar example is the `color{Violet}"corn cob"` – the `color{Violet}"tassels"` are nothing but the stigma and style which `color{Violet}"in the wind"` to trap pollen grains.

● `color{Violet}"Wind-pollination"` is quite common in `color{Violet}"grasses"`

POLLINATION BY WATER

● Pollination by water is quite `color{Violet}"rare in flowering plants"` and is limited to about 30 genera, mostly `color{Violet}"monocotyledons"`.

● On the contrary, water is a `color{Violet}"regular mode of transport"` for the male gametes among the `color{Violet}"lower plant groups"` such as algae, bryophytes and pteridophytes.

● It is believed, particularly for some `color{Violet}"bryophytes and pteridophytes"`, that their distribution is limited because of the need for water for the transport of male gametes and fertilisation.

● Some examples of water pollinated plants are `color{Violet}"Vallisneria and Hydrilla"` which grow in fresh water and several `color{Violet}"marine sea-grasses"` such as Zostera.

● Not all aquatic plants use water for pollination.

● In a majority of aquatic plants such as `color{Violet}"water hyacinth and water lily"`, the flowers `color{Violet}"emerge above"` the level of water and are pollinated by `color{Violet}"insects or wind"` as in most of the land plants.

● In Vallisneria, the female flower reaches the surface of water by the `color{Violet}"long stalk"` and the male flowers or pollen grains are `color{Violet}"released on to the surface"` of water.

● They are `color{Violet}"carried passively"` by water currents; some of them eventually reach the `color{Violet}"female flowers"` and the stigma.

● In another group of water pollinated plants such as `color{Violet}"sea grasses"`, female flowers remain `color{Violet}"submerged in water"` and the pollen grains are `color{Violet}"released inside"` the water.

● Pollen grains in many such species are `color{Violet}"long, ribbon like"` and they are carried `color{Violet}"passively inside the water"`; some of them reach the stigma and achieve pollination.

● In most of the water-pollinated species, pollen grains are protected from `color{Violet}"wetting"` by a `color{Violet}"mucilaginous covering"`.

● Both wind and water pollinated flowers are `color{Violet}"not very colourful"` and do `color{Violet}"not produce nectar"`.

POLLINATION BY ANIMALS

● Majority of flowering plants use a `color{Violet}"range of animals"` as pollinating agents.

● Bees, butterflies, flies, beetles, wasps, ants, moths, birds (sunbirds and humming birds) and bats are the `color{Violet}"common pollinating agents"`.



● Among the animals, insects, `color{Violet}"particularly bees"` are the `color{Violet}"dominant biotic"` pollinating agents.

● Even `color{Violet}"larger animals"` such as some primates (lemurs), arboreal (tree-dwelling) rodents, or even reptiles (gecko lizard and garden lizard) have also been reported as `color{Violet}"pollinators in some species"`.

● Often flowers of animal pollinated plants are `color{Violet}"specifically adapted"` for a particular species of animal.

● Majority of insect-pollinated flowers are `color{Violet}"large"`, `color{Violet}"colourful"`, `color{Violet}"fragrant"` and `color{Violet}"rich in nectar"`.

● When the flowers are small, a number of flowers are `color{Violet}"clustered into an inflorescence"` to make them conspicuous.

● Animals are `color{Violet}"attracted"` to flowers by `color{Violet}"colour"` and/or `color{Violet}"fragrance."`

● The flowers pollinated by `color{Violet}"flies and beetles"` secrete `color{Violet}"foul odours"` to attract these animals.

● To sustain animal visits, the flowers have to provide `color{Violet}"rewards"` to the animals.

● `color{Violet}"Nectar and pollen grains"` are the usual floral rewards.

● For harvesting the reward(s) from the flower, the animal visitor `color{Violet}"comes in contact"` with the anthers and the stigma.

● The body of the animal gets a `color{Violet}"coating of pollen grains"`, which are `color{Violet}"generally sticky"` in animal pollinated flowers.



● When the animal carrying pollen on its body comes in `color{Violet}"contact with the stigma"`, it brings about pollination.

● In some species `color{Violet}"floral rewards"` are in providing `color{Violet}"safe places to lay eggs"`; an example is that of the tallest flower of `color{Violet}"Amorphophallus"` (the flower itself is about `color{Violet}"6 feet"` in height).



● A similar relationship exists between a species of `color{Violet}"moth and the plant Yucca"` where both species – moth and the plant – cannot complete their `color{Violet}"life cycles"` without each other.

● The moth deposits its `color{Violet}"eggs in the locule"` of the ovary and the flower, in turn, gets `color{Violet}"pollinated by the moth"`.

● The larvae of the moth `color{Violet}"come out of the eggs"` as the seeds start `color{Violet}"developing"`.


 
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