How do plants make love?
Audio 03:43
By foraging on the flowers of a cherry tree, then another, these two bees will carry the pollen necessary for fertilization.
© RFI / Florent Guignard
By: Florent Guignard
7 mins
In spring, the mating season, many plants flower and begin the cycle of their reproduction.
Vegetal sexuality is a game of chance, in which pollen has an essential role, as well as some animals.
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A bee gathers a cherry blossom.
Then another… Ordinary spring scene in a temperate climate.
Spring, the season of love, when the sap rises under the effect of the heat and the returning sun.
Even plants make love.
A form of virtual sex.
Without touching each other, since plants cannot move - this is what first distinguishes them from animals.
And this is where the bee comes in, whose legs and hairs are now covered with a white powder.
Pollen.
A pollen grain is like a plant sperm: it is it, tiny, produced in quantity by the stamens (the male organs of the flower) and deposited further by our bee on the pistil (the female organ) of another flower, which will give birth to a fruit, a seed.
"Look how beautiful I am"
The vast majority of flowering plants are therefore adept at threesomes.
Their reproduction cannot be done without the help of an insect, which invites itself into the game, a butterfly, a beetle, but also a bird (the famous hummingbird, chickadees ...) and even a mammal, the bat .
In this game of plant love, there is no point in pleasing your partner, whom you will never know.
And yet, with their colors, their shapes and their scents, the flowers seem to say: “
Look how beautiful I am
!
It is because it is a question of seducing the pollinators, with the key reward: pollen, which contains proteins, and nectar, full of sugar.
An exchange of good practices: I feed you, said the plant to the bee, if you help me make love.
The game of love and chance
But other plants do very well without pollinating auxiliaries.
Their flowers are also tasteless and tiny.
They practice ultimate risk-free sex.
They are anemophiles, like pines, grasses.
The wind disperses the grains of their pollen, produced by the millions to increase the chances of fertilization, up to hundreds of meters.
The game of love and chance ...
But pollens can cause some concern for humans.
A recent study has just shown that the presence of pollens in the air we breathe increases the risk of contamination with Covid-19, because pollens act on the immune system, in the same way as air pollution. leads to the risk of allergy to pollen.
The "hay fever", the itchy eyes, the runny nose, this disease which affects up to 30% of the world population, appeared with the industrial revolution of the XIXe century.
In France, the pollen allergy season started with cypress trees.
Earlier and earlier because of global warming.
The onset of flowering is three weeks earlier today than 20 years ago.
In London, to prevent the seeds and fruits of the trees from dirtying the sidewalks, they wanted to remove the female flowers by favoring cloned male species.
The result: even more pollen, and even more hay fever.
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