Without pollination, the selection of fruit and vegetables on our plates would be surprisingly small, which is why in this article we will explain to you what exactly plant pollination is, how it works - and why pollination and fertilization are not the same thing.
What is plant pollination and how does it work?
Plant pollination is the process by which pollen is transferred from male flowers to female flowers to enable reproduction and formation of fruits and seeds. This pollination occurs through natural helpers such as insects, birds, wind or water and is fundamental for biodiversity and food production.
- Pollination refers to sexual reproduction in plants
- various forms, basic distinction between self-pollination and external pollination
- all plants need help with pollination, usually from insects or wind
- Not only bees pollinate plants, but also bumblebees, butterflies, moths, beetles, flies etc.
- many plant species have specialized in pollination by certain insects
What is pollination?
As with humans and many animals, there are two different sexes in plants, whose genetic makeup comes together during pollination - the male pollen is transferred to the female ovule (stigma) in different ways. This is where the pollen germinates and grows through the flower style. This contains the embryo sac cell, in which male and female cells finally fuse together. After successful fertilization - because this is what it is - the fruits containing seeds then form. The reproduction was successful.
Excursus
Is there a difference between pollination and fertilization?
Even though these two terms are often used interchangeably, they do not mean the same thing: pollination simply describes the exchange of pollen or pollen between flowers; fertilization only occurs afterwards through the fusion of female and male sex cells. Not every pollination is crowned with fertilization, but without pollination fertilization is not possible.
Types of pollination
Kiwi flowers are dioecious (here: female flowers)
Basically, the biologist distinguishes between monoecious and dioecious plants:
- monoecious plants: female and male flowers are on the same plant (hermaphrodite), appear either at the same time or at different times
- dioecious plants: there are male and female plants, each specimen only produces flowers of one sex
Depending on the abundance of a plant species, its type of pollination is determined, although there are two different options. Monoecious species are capable of self-pollination (as long as the flowers of different sexes are formed at the same time), while dioecious species always rely on cross-pollination by animals - usually insects - or wind.
Self-pollination
Self-pollinators are able to develop male and female genes themselves and thus pollinate themselves - so they are not dependent on a second plant of the same species. Therefore, they are always monoecious plants that bear both male and female flowers. However, these plants also need insects, wind or other aids to transfer the pollen to the female flowers.
The advantage of self-pollination is that entire colonies can quickly grow from a single plant specimen. That's why this ability is often found in pioneer plants - i.e. H. in species that first colonize fallow areas - or in early bloomers. Typical self-pollinators are therefore peas, beans and barley. The snowdrop and the anemone also belong to this group.
Tip
Many fruit trees are also capable of self-fertilization. However, the harvest is often significantly better if a second pollinator plant is available.
Cross-pollination
Bees are probably the most well-known pollinators
Foreign pollinators, on the other hand, are not able to fertilize themselves. Here the male pollen from one plant must pass to the female ovary of another - otherwise a fusion of the genetic makeup is not possible. In contrast to self-pollination, cross-pollination has the advantage that the genetic diversity is greater and therefore the species' ability to adapt to its environment is greater. Cross-pollinators are always found in dioecious plants, but many monoecious species also fall into this group - for example when they bear male and female flowers at different times.
Some species are even capable of both and can pollinate themselves as well as other specimens of their own variety. But regardless of whether self-pollination or external pollination: all plants rely on outside help in this process. The pollen must either pass through
- Insects such as bees, bumblebees, butterflies, beetles
- animals of various species that happen to pass by (and take pollen with them)
- Birds (e.g. hummingbirds) and nectar-sucking bats
- Elements such as wind or water
transferred. Most plant species prevent self-pollination because it is evolutionarily less successful than cross-pollination. Ergo, self-pollination is a kind of solution when a suitable pollinator is not available.
Insect pollination
Butterflies also pollinate flowers
“If the bee dies, does the person die? This quote is incorrect for several reasons!”
Many plants rely on the diligent help of various types of insects for pollination. “Insect-flowered” species can be recognized by typical flower characteristics such as
- bright, colorful flower colors (especially red, pink, yellow, violet or blue)
- strongly scented flowers
- special flower shapes
These characteristics serve to attract pollinating insects. Many plant species have specialized in pollination by certain insects, so that for example
- Nectar composition
- Flower shapes
- Flowering time and duration
are precisely adapted to the flight times, hatching times and needs of the pollinator insects.
It is common knowledge that bees pollinate plants. However, many people are less aware that it is not only bees that take on this important task - but also bumblebees, butterflies, moths, beetles, flies and other insects. Scientific studies have shown that in many cases pollination occurs less by bees and more by other species - or is more successful when different types of insects cavort on the flowers. For this reason, the oft-quoted saying that after the bees died out there would soon be no plants left and four years later humans would also die is simply wrong. Not to mention that Einstein (to whom the quote is attributed) never claimed this.
Excursus
Why do we talk about the death of bees? Will the honey bee soon no longer exist?
Many people spontaneously think of the honey bee when they hear the word “bee”. However, this is not what is meant when it comes to the death of bees or, more generally, insects. In fact, honey bees are farm animals and as such are not threatened with extinction. Instead, the death of bees refers to the approximately 560 different species of wild bees, which - together with other insect species such as bumblebees, butterflies and beetles - are also much more important for the pollination of plants than honey bees.
There is no "one" cause for the death of insects, although factors such as industrial agriculture with its gigantic monocultures and the use of pesticides and other poisons as well as the disappearance of flowering plants from gardens - in their place increasingly lawns and "Gravel gardens” play a major role. These developments rob insects of both food and hiding and nesting opportunities.
The following video on the subject of alternative pollination clearly shows what happens when there are no more bees:
Wind pollination
The evolutionarily oldest form of pollination is wind pollination: In the primeval forests, which initially only had conifers - deciduous trees only emerged much later - the wind blew the pollen to the female flowers. For this reason, all conifers are still wind-pollinated today - many other species such as birch, poplar, alder and hazelnut bushes only developed this form afterwards. Typical characteristics of wind-pollinated plants are:
- hanging, long catkin flowers
- these are always male and carry millions of pollen
- these are often recognizable as pollen
- female flowers are inconspicuous
- do not have petals or similar ornaments
- and only carry a few ovules
- no nectar is produced
Other typical representatives of wind-pollinated species are grasses, sedges, rushes and the nettle family.
Frequently asked questions
What is meant by water pollination?
Water pollination (also water flowering or hydrophilicity) is the name given to the pollination of aquatic plants by water. Through its movements, this ensures that pollen is transported from one flower to another. This phenomenon only occurs in a few aquatic plants, which you can recognize by their inconspicuous flowers. Examples of this are the large mermaidweed (Najas marina), the common seaweed (Zostera marina) or the various waterweed species (Elodea).
How can you help bees and other insects?
The greatest possible variety of flowers attracts pollinating insects to the garden
If you want to do something about the death of bees or insects, you can do so with a few simple measures: do not use pesticides or other toxins in the garden, cultivate the garden as close to nature as possible and offer hiding places (dead wood, piles of stones, sandy areas, Insect hotel etc.), sow or plant many flowering plants (with unfilled flowers!) - umbelliferous plants in particular are popular with insects, but also flowering shrubs, ensure plenty of flowering plants early and late in the year (flowering period from March and from July to October into it).
Why is it not a good idea to buy wild bees and resettle them artificially?
Basically, this idea sounds tempting: you simply buy wild bees of certain species and settle them in your garden - and you're already doing something about the death of bees. Unfortunately, it's not that simple, as many nature conservation organizations emphasize. Because by artificially settling wild bees you are not promoting biodiversity, but rather endangering it.
Why? Because the purchased bees displace native species (and thus their gene pool)! This even applies if it is the same species, because different populations from different regions also have different genetic information - and are also adapted to their respective homeland through evolution.
Are there plants that can survive without pollination?
No plant can survive without pollination. However, there are many plants that do not require pollination by insects. An estimated 60 percent of all flowering plants worldwide need bees etc. to reproduce - for 40 percent, other helpers such as the wind do this. When it comes to our food plants, this applies to grains such as wheat, rye and barley, but also to legumes such as peas and beans. Without insect pollination, however, our table would be less rich, as most types of fruit (such as apples, pears, cherries or strawberries) rely on cross-pollination.
Tip
If you are interested, you can also work as a beekeeper and keep honey bees - this is even financially supported by the state! Just ask your local beekeeping association.
