2023-04-27 20:45:12
The dry and hot beginning of spring has caused a significant increase in pollen levels, one of the most common allergens on the European continent. Despite their tiny size – and being a nightmare for allergy sufferers – pollen grains fulfill an essential ecological function for the survival of humanity. It is time to value it as it deserves.
The spark that ignites plant life
More than 350 million years ago, a lineage of plants, the gymnosperms (with naked seeds, such as firs, cedars and pines), developed grains of pollen and seeds, marking a before and after in reproduction and adaptation to the terrestrial environment. of the vegetable kingdom.
Two hundred million years later, in the midst of the terrestrial revolution of the Cretaceous, plants with flowers and seeds protected by fruits appeared: the angiosperms. Thanks to the evolutionary ingenuity of pollen and flowers and their co-evolution with pollinators, angiosperms diversified rapidly, dressing the planet in a multitude of vibrant colors. They are the ones that today dominate terrestrial ecosystems and the main protagonists of farmland.
More than an allergen
Pollen, that often golden dust that wafts through the air in spring and summer, is actually a tiny but powerful reproductive structure.
The mature pollen grain is the male gametophyte of plants. It contains three cells, two spermatic and one vegetative, protected by a double envelope that gives it resistance. It is produced in the male organs of angiosperms (stamens) and gymnosperms (male cone).
The pollen grain functions as an intermediary that transports the male genetic material from the producing plant to the female organs of other plants, or to itself, in some cases. This is how fertilization and seed production are achieved.
Since the chances of a pollen grain landing on an ideal mate are slim, plants tend to produce a lot of pollen. And as we know, and even suffer from, this overproduction has consequences that go beyond plant reproduction.
Wikimedia commons
Love is in the air
Pollen production is finely orchestrated by environmental conditions such as temperature, humidity, and light, as well as the plant’s hormonal status. But in addition, the dance of pollinators around the plant can also encourage pollen production.
As the pollinator moves from flower to flower in search of nectar, its body is loading and unloading pollen grains that are deposited on the pistils of the flowers (specifically on the stigmas), increasing the possibility of fertilization and the seed formation. Indeed, in plants, love is in the air.
To increase reproductive success, plants have been creating an astonishing variety of structures, shapes, and colors for their pollen grains, which are closely related to dispersal mechanisms and pollinators.
Thus, the most visible and heavy pollen grains, and also those provided with small spines and a sticky surface, are generally transported on the backs of large pollinators such as bees (entomophilia) and birds (ornithophilia). On the other hand, those that are smaller, lighter, spherical and winged are transported by the spring breeze (anemophilia).
Pigments such as flavonoids and/or carotenoids are behind the reddish-bluish and/or yellow-orange color so common in pollen grains, which makes them even more attractive to pollinators. Furthermore, it should not be forgotten that, along with nectar, pollen is also collected by pollinators as a food rich in protein, lipids and carbohydrates.
What would the world be without pollen?
Pollen plays a crucial role in agriculture, especially in the production of fruits, vegetables and grains. It is estimated that more than 75% of the world’s food crops depend to some extent on pollination (transfer of pollen). Therefore, a large part of our diet is at stake. Every seed, grain, and fruit we eat is a direct product of pollination.
Without pollination, crops would not produce viable seeds, which would reduce their yield and lead to significant economic losses. In a scenario of high demand for food due to the increase in the world population, we cannot neglect pollen or the work of pollinators.
As pollinating agents, bees, butterflies, birds, moths, beetles and even bats influence the stability and plant diversity of ecosystems and the yield (quantity and nutritional quality) of crops in agroecosystems.
As small as pollen grains and pollinators are, they play a big role in achieving several of the Sustainable Development Goals (SDGs) set by the UN, from fighting hunger and poverty to creating jobs and economic growth.
.Capiro. / Flickr, CC BY-NC-ND
The perfect storm on a planetary scale
Unfortunately, the fragmentation and destruction of habitats, the use of pesticides and climate change are causing the perfect storm on a planetary scale: a decrease in plant diversity, a reduction in pollen quality and a decline in pollinator populations.
What can we do? Restoring and conserving habitats, restricting pesticide use, enhancing biological pest control, and diversifying farms to create a balanced ecosystem for bees and their fellow pollinators. We have a lot of work ahead of us.
#power #pollen