Pollination (part 4)

Flower shape and nectar provision

Flower pollination is also aided by the very shape of the flower, and the way in which insects come into contact with its sexual parts (the carpels and stamen). For example, even within the bee families, the shapes, sizes and weights of the bees vary, as do the tongue lengths.

Whilst honey bees have quite short tongues for sucking up nectar, some of the bumblebees have long tongues, meaning they may target deep, tubular shaped flowers. For example, with their furry, roundish bodies, they are ideal pollinators for foxgloves, their coats being efficient catchers of pollen as they make their way up inside the flowers.

Flowers have different nectar re-fill rates - yes, once the nectar is taken by one insect, the flower may replenish the nectar ready for the next passing insect. This helps to ensure that a plant can be visited more than once, increasing its chances of pollination.

 However, insects may cheat the plant!

In cases where short tongued bumblebees cannot get at nectar stores in the base of flowers, they may bite a hole, and access the nectar in that way. This is called ‘nectar robbing’. The hole may then be visited by other insects also keen to take the nectar, as the nectar supply is replenished. This is called ‘secondary robbing’.

Opinions vary, but some state that flower pollination is not necessarily hindered, because the flower may still be targeted by other bees that are engaged in gathering pollen, rather than nectar.

On the other hand, flowers may cheat insects too!

The Bee Orchid (Ophyrys apifera) is believed to have evolved to emulate the appearance of the female bee of the species required to pollinate it. The male bee lands on the female with the intention to mate. In his attempt, the orchid is pollinated. The bee, however, is disappointed!

Orchid pollination is not only carried out by bees. Certain beetles such as the beetle Strangalia maculata , are also able to assist in orchid pollination, as they can efficiently access the complex flower structures of some wild orchids.

Buzz about bee net

Pollination (part 3)

It’s well known that insects have a vested interest in visiting flowers – that is, they’re not merely visiting the flowers with the altruistic intention of performing a passing pollination service. They’re usually gathering nectar and/or pollen. Thus both the plant and insect benefit from their relationship with each other.

However, flowers come in all sorts of shapes and sizes, and so do insects. The flowers vary their features to appeal to their target visitors. When flowers have adapted to attract certain pollinators, they are said to have developed ‘pollination syndromes’.

Scent

Humans love fragrance, and so do insects. But different insects like different fragrances. On the one hand, sweet peas have a scent that can charm the bees. Butterflies also like fresh, but very delicate scents.

A number of flowers produce what humans would consider to be a foul stench. For example, the Vodoo Lily - Sauromatum guttatum (pictured), from the ‘Aroideae’ plant family, emits an odour that is likened to rotting flesh.

From a different plant family, the Orontiods, the Eastern Skunk Cabbage (Symplocarpus foetidus) and Western Skunk Cabbage (Lysichiton americanus), are also said to give off the horrible odour of decaying flesh.  Primarily carrion flies and beetles (i.e. flies and beetles that are attracted to dead and rotting bodies of animals etc.).

The time of day also plays a role in attracting pollinators. In some cases, flower pollination actually takes place in the evening. Flowers pollinated by bats and moths, for example, are strongly scented at night, such as night-scented Stocks, Evening primrose, and  Jasmine (Jasminum officinale).

Colors and patterns

 Like humans, bees are trichromatic. This means their eyes (like ours) have 3 color receptors. However, whereas humans base their color vision on the color receptors red, green and blue, bees base their color vision on Ultra Violet, blue and green.

Although bees cannot see red, however, they do visit red flowers. Why? Because flower petals have Ultra Violet patterns on them, not visible to humans in normal light, but visible to bees. The patterns are believed to guide the bees onto the flower ‘landing platform’, and then into the flower. With regard to red flowers, bees may also use other cues, such as scent. However, all in all, it is also thought that bees prefer different shades of blues, whites, and purple flowers.

In general, it’s believed that swathes of color are also more helpful to foraging bees and butterflies, providing a stronger visual signal that suggests ‘plenty of food here’ , and of course, it is more energy efficient for bees and other pollinators to find areas of denser food provision.

Buzz about bee net

Pollination (part 2)

There are 2 type of pollination

Abiotic

Abiotic pollination refers to situations where pollination is mediated without the involvement of other organisms. Only 10% of flowering plants are pollinated without animal assistance. The most common form of abiotic pollination, anemophily, is pollination by wind. This form of pollination is predominant in grasses, most conifers, and many deciduous trees. Hydrophily is pollination by water and occurs in aquatic plants which release their pollen directly into the surrounding water. About 80% of all plant pollination is biotic. In gymnosperms, biotic pollination never takes place. These plants always exhibit anemophily that is wind pollination. Of the 20% of abiotically pollinated species, 98% is by wind and 2% by water.

Biotic

More commonly, the process of pollination requires pollinators: organisms that carry or move the pollen grains from the anther to the receptive part of the carpel or pistil. This is biotic pollination. The various flower traits (and combinations thereof) that differentially attract one type of pollinator or another are known as pollination syndromes.

There are roughly 200,000 varieties of animal pollinators in the wild, most of which are insects.Entomophily, pollination by insects, often occurs on plants that have developed colored petals and a strong scent to attract insects such as, bees, wasps and occasionally ants (Hymenoptera), beetles (Coleoptera), moths and butterflies (Lepidoptera), and flies (Diptera). In zoophily, pollination is performed by vertebrates such as birds and bats, particularly, hummingbirds, sun birds, spider hunters, honey eaters, and fruit bats. Plants adapted to using bats or moths as pollinators typically have white petals and a strong scent; while plants that use birds as pollinators tend to develop red petals and rarely develop a scent (few birds have a sense of smell).

Insect pollinators such as honeybees (Apis mellifera), bumblebees (Bombus terrestris), and butterflies (Thymelicus flavus) have been observed to engage in flower constancy, which means they are more likely to transfer pollen to other con specific plants. This can be beneficial for the pollinisers, as flower constancy prevents the loss of pollen during inter specific flights and pollinators from clogging stigmas with pollen of other flower species.

Pollination (part 1)

Pollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Pollen grains, which contain the male gametes (sperm) to where the female gamete(s) are contained within the carpel in gymnosperms the pollen is directly applied to the ovule itself. The receptive part of the carpel is called a stigma in the flowers of angiosperms. The receptive part of the gymnosperm ovule is called the micropyle. Pollination is a necessary step in the reproduction of flowering plants, resulting in the production of offspring that are genetically diverse.