Our precious pollinators
The basic principles of pollination are easily understood: grab some pollen grains from the male parts of a flower (the anther) and somehow deposit those on the top of the female reproductive centre (the stigma). Once a pollen grain sticks to the stigma it produces a long pollen tube down the length of the style until it reaches the female gametophytes, where fertilisation takes place.
You can make the story as complicated as you like, but the upshot of this system is that fertilisation of flowers results in genetically diverse offspring, meaning there will be variabilities in the plants that emerge from the seeds.
Pollination, then, is the way in which the pollen grains are delivered to the stigma and style. About 20 per cent of plants rely on wind and water to do that job and some 80 per cent of all plant species simply grab the services of a pollinator from the animal kingdom. We’re talking birds and lizards, small primates, rodents, bats and a whole line-up of bugs. And, as you guessed, it’s the invertebrates (especially insects) that really do a stand-out job here.
To attract the right kind of pollinator, a plant has to have one or more tricks in its arsenal. A colour which insects can see is handy. Blue or white (and all the shades in between) are the best, as insects’ eyes appear to be pretty poor at detecting the orange and red spectral ranges.
A good smell plays right into the antennae too. These long feelers are very sensitive organs that can detect a few molecules of the right chemical and then excite and guide the owner.
A nicely shaped flower can be attractive to an insect: there are fabulous examples of bee orchid flowers looking like a female bee, which could be mounted by an alert male bee… Sorry mate!
And then there is the reward for the pollinator – quick sustenance, a decent dose of fructose (energy) and a sweet nectar that forms a building block for making honey.
Of course, the pollen is chock-full of protein that is useful for growing new insect bodies. Some pollinators are really only interested in pollen to stock the nursery for their larvae to eat.
The honeybee ( Apis mellifera) is by far the world’s most important pollinator of human food crops – about one-third of our food has had some input from these insects. Their amazing work involves not just collecting and distributing pollen, but also turning nectar into nutritious and medicinal honey.
Why is honey so good for us and how do these clever bees produce this miracle material? In this case the honours must go to the plants, dear gardener. Nectar is the ‘‘reward’’ plants make for the pollinator’s services. Imagine what would happen if a pollinator finds its reward spoilt, smelling of fungal rot and crawling with germy slime? I reckon the bee (and other pollinators for that matter) would soon give the incompetent plant species a wide berth. This, of course, jeopardises the plant’s long-term future on this planet. To prevent the nectar from spoiling, plants cram it full of antibacterial, anti-fungal and antimicrobial substances to keep it in fabulous condition. All the bee has to do is gather it and turn it into honey. Shows you the importance of using top-notch ingredients!
Large garden bumblebee, Bombus ruderatus