The author of the text is MSc. Beata Romanowska
The most intense smell is essential oils, which are biosynthesized and released into the atmosphere by most green plants, some fungi and bacteria.Their amount emitted to the atmosphere by the land flora during the year is estimated at 360 million tons.Nevertheless, the content of oils in individual species is usually small, e.g. from 100 kg of lavender you can distil approx. 2 , 5 kg of oil, and for 100 kg of rose petals no more than 0.5 kg.
So why do plants smell? The most important reason is to attract animals to participate in the pollen transfer process, i.e. pollination of plants.In the case of sexual reproduction of plants, cross-pollination seems to be the most advantageous, i.e. with pollen of the same species but of a different individual, which allows for obtaining a combination of features of both parents in the offspring.Pollen can be carried by wind, water and animals.Insects play this role most often, but there are also flowers whose pollen is carried by snails, birds, bats.
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Tysięcznik Gałęzisty Centaurium Pulchellum (Photo: Fotolia.com) |
Plants have developed various methods of attracting animals participating in their pollination - most often using the colors, smells and shapes of flowers. On the other hand, animals - mainly insects and birds - receive nectar or pollen from plants, which they feed on, as if in the form of "payment for services", and sometimes it is only a sweet promise, because these smells often resemble the smell of sex pheromones.
And we? We can admire the beauty and feel the joy of stimulating the senses ( although sometimes the smells emitted by plants are unbearable for us, e.g. pictures of Arum nigrum emit a terrible carcass smell, attracting certain beetles).But the benefits of plant fragrances are more tangible to us, e.g. in aromatherapy we use fragrances to maintain the body's resistance to diseases and to improve well-being.
Natural essential oils can also be purchased in a small form, for infusing rooms
Odor as a protective mechanism
The reason why plants emit odors is their protection against pests.Volatile oils contain antiseptics that protect against microbes and animal parasites.They have a microbicidal effect on gram (+) and gram ( -), yeasts, molds, actinomycetes, viruses and protozoa. It has also been observed that highly aromatic plants are reluctantly eaten, e.g.Hymenoptera and ants do not like the smell of mint, and mosquitoes do not like the smell of pine.
Another function is the filtration of sunlight reaching plants. In our climate, you can observe a violet-blue oil halo over large plant clusters, e.g. pine forests. It is credited with protecting it from the red radiation of the spectrum, which heats the leaves and increases transpiration.
Fragrances are found in all parts of plants - flowers, leaves, stems, roots, fruits and seeds. They are stored in special external reservoirs (glands, hairs, honey cells), e.g. in plants from the labial family, or inside the plant, among the crumb cells as resin channels, milk pipes, resin cells, mucous cells, oil cells (e.g. in the family of laurel plants,In some plants, such as roses, violets, and lilies - the oil is produced only in the cells of the skin and directly underneath it, and it evaporates quickly, therefore, after drying, the petals of these plants lose their smell.
The petals of the crown are usually the seat and source of fragrances in a flower. The oil glands are located on them variously: in the orchid Maxillaria rufescens they are located only on the edges of the petals on their lower side, in Aristolochia grandiflora - at the base of the flower tube.Their structure is similar to the nettle stinging glands - after touching them, the tip breaks off, taking the shape of a sharp needle and oily substance is poured out (in the case of stinging nettle).Numerous studies have shown that individual parts of the flower may give off different odors, e.g. in primula Primula acaulis the inner part of the crown smells different than the outer part.
Oil composition
Essential oils are a complex mixture of organic compounds with 100 to over 300 ingredients in one oil. It is assumed that they belong mainly to terpenes and their oxygen derivatives (alcohols, ketones, esters).
When do plants smell the most intense?
The intensity and duration of the fragrance depends on the stage of plant development. In the period of maturity, pollen is the most intense. The quality of the fragrance also changes with age, e.g. ripe coriander smells nice, but at a young age it smells like bedbugs.The content of oils in a plant also depends on environmental conditions - temperature, humidity, length of the day, as well as the substrate on which plants grow, e.g. lavender oils come from France and rose - from Bulgaria.
In the course of evolution, insects and plants have adapted to each other's periods of activity. It is difficult to say today whether plants have adapted to animals or vice versa.In any case, different species of flowers open only at one specific time of the day or night, which is related to the activity of the animals pollinating them.This phenomenon was used to arrange flower clocks (their precursor was Carl Linnaeus) : e.g.at 4-5 am wild rose Rosa canina opens flowers, at 5-6 flax Linum usitissimum, at 6-7 kiprzyca willow, at 8-9 sorrel, at 9-10 tulip, at 10-11 thousand centaurium pulchellum, and at 11-12 erect cinquefoil Potentilla recta. Some species of flowers do not open until afternoon or evening. The latter include Matthiola maciejka and Nicotiana tobacco.
Each plant species also produces the most abundant nectar and pollen secretion for a strictly defined period of time, e.g. a rose produces the most pollen between 7-11 am, opium poppy 6-9, and verbena from 7-12.
Smell and color
Plants lure insects first with the color of flowers. It is only when the insects are nearby that the smell becomes significant, allowing them to distinguish plant species and assess whether they contain nectar. This applies to insects that are active during the day, such as butterflies.The flowers pollinated by them are bright - relatively dark - red, orange, yellow, blue, purple. Often their crowns close at dusk, like gentian or carnation.
On the other hand, flowers pollinated by night butterflies have bright crowns - white, yellowish, pale blue, pink. They give off a strong, often intoxicating scent that attracts butterflies, even from a distance, because moths have olfactory organs more developed than diurnal butterflies.
Such flowers are: maciejka, garden tobacco, tuberose, drilling honeysuckle, garden yucca. White-flowering lilies, narcissus Narcissus poeticus, white-flowering forest orchid Platanthera bifolia are exclusively pollinated by moths, which emit an intoxicating fragrance that intensifies in the evening.
