Without pollination, the choice of fruits and vegetables on our plates would be surprisingly limited, which is why in this article we explain to you exactly what plant pollination is, how it works - and why pollination and fertilization are not the same.

Not only bees pollinate flowers

Table of Contents

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  1. the essentials in brief
  2. What is pollination?
  3. types of pollination
  4. frequently asked Questions

    5. the essentials in brief

    • Pollination refers to the sexual reproduction of plants
    • diverse forms, fundamental distinction between self- and cross-pollination
    • all plants need help with pollination, usually by 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 also two different sexes in plants, whose genes come 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 handle. This is where the embryo sac cell is located, in which male and female cells finally fuse with each other. After successful fertilization - because this is the type of fertilization - the seed-containing fruits then develop. The reproduction was successful.

    digression

    Is there a difference between pollination and fertilization?

    Even if these two terms are often used synonymously, they do not mean the same thing: Pollination only describes the exchange of pollen or pollen between flowers, fertilization only takes place afterwards through the fusion of female and male gametes. Not every pollination is crowned by fertilization, but fertilization is not possible without pollination.

    types of pollination

    Kiwi flowers are dioecious (here: female flowers)

    Basically, the biologist distinguishes between monoecious and dioecious plants:

    • monoecious plants: male and female flowers are on the same plant (hermaphrodite), appearing either at the same time or at different times
    • dioecious plants: there are male and female plants, one specimen only produces flowers of one sex

    The type of pollination depends on the abundance of a plant species, whereby there are two different possibilities. Monoecious species are capable of self-pollination (provided the opposite-sex flowers are formed at the same time), while dioecious species always depend on cross-pollination by animals - mostly insects - or wind.

    self-pollination

    Self-pollinators are able to develop male and female hereditary factors themselves and thus pollinate themselves - they are therefore not dependent on a second plant of the same species. That is why they are always monoecious plants that carry both male and female flowers. However, these plants also need insects, wind or other means to transfer the pollen to the female flowers.

    The advantage of self-pollination is that entire colonies can grow very quickly from a single plant specimen. Therefore, this ability is often found in pioneer plants - i. H. in species that colonize fallow land first - or in early bloomers. Typical self-pollinators are therefore peas, beans and barley. The snowdrop or the anemone also belong to this group.

    tips

    Many fruit trees are also capable of self-pollination. However, the harvest is often significantly better if a second pollinator plant is available.

    cross-pollination

    Bees are probably the best-known pollinators

    Cross-pollinators, on the other hand, are not able to fertilize themselves. Here the male pollen of one plant must be transferred to the female ovary of another - otherwise a fusion of the hereditary factors is not possible. In contrast to self-pollination, cross-pollination has the advantage that there is greater genetic diversity and thus the ability of the species 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, if they bear male and female flowers at different times.

    Some species are even capable of both, pollinating themselves as well as other specimens of their own variety. Regardless of whether it is self-pollination or cross-pollination, all plants are dependent on outside help for this process. The pollen must either go through

    • Insects such as bees, bumblebees, butterflies, beetles
    • randomly passing animals of different species (taking the pollen with them).
    • Birds (e.g. hummingbirds) and nectar-sucking bats
    • elements like wind or water

    be transmitted. Most plant species avoid self-pollination because it is evolutionarily less successful than cross-pollination. Ergo, self-pollination is a kind of workaround when no suitable pollinator is available.

    insect pollination

    Butterflies also pollinate flowers

    “Does the bee die, does man die? This quote is wrong for several reasons!”

    Many plants rely on the diligent help of various insect species 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 the pollinating insects. Many plant species have specialized in pollination by certain insects, so that about

    • nectar composition
    • flower shapes
    • flowering time and duration

    are precisely adapted to the flight times, hatching times and needs of the pollinating insects.

    It is well known that bees pollinate plants. On the other hand, many people are less aware that not only bees take on this important task - but also bumblebees, butterflies, moths, beetles, flies and other insects are active. Scientific studies have shown that in many cases pollination is less by bees than by other species - or is more successful if different species of insects cavort on the flowers. For this reason, the frequently quoted saying that after the bee dies out there will soon be no more plants and four years later man will also die is simply wrong. Quite apart from the fact that Einstein (who is credited with the quote) never claimed this either.

    digression

    Why are we talking about bee deaths? Will the honey bee be gone soon?

    Many people 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 in danger of extinction. Instead, the bee deaths relate to the approximately 560 different species of wild bees, which - together with other insect species such as bumblebees, moths and beetles - are also much more important for pollination than honey bees.

    There is no such thing as "the" cause of insect deaths, but factors such as industrial agriculture, with its gigantic monocultures and use of pesticides and other toxins, and the disappearance of flowering plants from gardens - which are increasingly being replaced by lawns and "gravel gardens" - play one major role. These developments deprive insects of both food and places to hide and nest.

    The following video on the subject of alternative pollination shows what happens when there are no more bees:

    youtube

    wind pollination

    The oldest form of pollination in evolutionary terms is wind pollination: In the primeval forests, which initially only contained coniferous trees - deciduous trees only formed much later - the wind blew the pollen to the female blossoms. For this reason, all conifers are still wind-pollinated today - many other species such as birches, poplars, alders and hazelnut bushes only developed this form afterwards. Typical characteristics of wind-pollinated plants are:

    • hanging, long catkins
    • these are always male and carry millions of pollen
    • these are often recognizable as pollen
    • female flowers are inconspicuous
    • have no petals or similar ornaments
    • and bear only a few ovules
    • no nectar is formed

    Other typical representatives of wind-pollinated species are grasses, sedges, rushes and nettle plants.

    frequently asked Questions

    What is water pollination?

    Water pollination (also water flowering or hydrophilicity) is the pollination of aquatic plants by water. With its movements, this ensures that the pollen is transported from one flower to the other. This phenomenon only occurs with a few aquatic plants, which you can recognize by their inconspicuous flowers. Examples of this are the mermaid (Najas marina), 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 against the death of bees or insects, you can do so with a few simple means: do not use any pesticides or other toxins in the garden, manage the garden as naturally as possible and offer hiding places (dead wood, piles of stones, sandy areas, insect hotel (11.33 €) etc.), sow or plant many flowering plants (with single flowers!) - umbellifers 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 the into October).

    Why is it not a good idea to buy wild bees and repopulate 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 to stop the bees from dying. Unfortunately, it is not that simple, as many nature conservation organizations emphasize. Because by artificially settling wild bees you do not promote biodiversity, but endanger it.

    For what reason? 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 also plants that get by without pollination at all?

    No plant can do 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 and co. for their reproduction - in 40 percent this is done by other helpers such as the wind. In the case of our food plants, this applies to cereals such as wheat, rye and barley, but also to legumes such as peas and beans. Without insect pollination, however, our table would be less richly set, since most types of fruit (such as apples, pears, cherries or strawberries) depend on cross-pollination.

    tips

    If you are interested, you can also be a beekeeper and keep honey bees - this is even financially supported by the state! Just ask your local beekeeping association.

Category:

Animals in the garden