Plant life in nature in spring. Why do wind-pollinated trees and shrubs bloom early in spring? How plants bloom
Introduction.
Spring, especially April and the first half of May, is a very suitable time for ecological studies of plants. During this period, transitional from winter to summer, you can see a wide variety of natural phenomena, moreover, in middle lane In Russia, where we live, all processes are going so fast that many of them can be traced in development, and sometimes even from beginning to end.
In spring, the ecological diversity of communities is extremely fully revealed, and some groups of organisms can be observed only in spring, for example, ephemeroids. And the conditions for research are favorable - at this time, as a rule, the weather is dry and warm.
Scientists distinguish several groups of plants blooming in spring: (Biology at school No. 2, 1998 // Primroses: a research project for schoolchildren, p. 67)
1) Early spring plants, developing and flowering in early spring, soon after the snow melts or even at the same time, long before the leaves bloom in trees and shrubs and most herbaceous plants, calendar - April and the first half of May (corydalis, goose onion, anemone, violets).
2) spring plants, giving flowers after the first group or at the time of their flowering, calendar - in the second half of May (sour, raven eye, petrov cross).
3) Late-spring plants blooming already in the beginning and second decade of June (fragrant woodruff, two-leaved wild rose, wild rose, honeysuckle, etc.) This paper presents the results of studying the first group of plants, i.e. early spring plants.
Objective: study of early spring flowering plants and their ecological groups.
Tasks:
- identify species of early spring plants;
- determine the frequency of their occurrence;
- make a herbarium;
- give a biological description of the species;
- establish ecological groups of early spring flowering plants;
- identify plant species in need of protection;
- formulate recommendations for rational use and protection of early spring plants.
The study was conducted 2 kilometers east of the village of Kazachy, Prokhorovsky district, from April 1 to May 10.
Research methodology
The study of the territory for the detection of early spring flowering plants was carried out by the route method. The routes covered the eastern territory of the vicinity of the village and all the main habitats: forest edges, glades, meadows, ditches along the roads, wastelands. The research was carried out in the period from April 1 to May 10, access to the route was carried out twice a week.
In the process of work on the route, the frequency of occurrence of these plants was recorded, the records were kept by eye, all plant species were divided into three groups: they are common and abundant, they are moderately frequent and rare.
Also, along the route, the habitats of plants and their need for certain environmental factors were noted, for the subsequent determination of ecological groups.
Herbarium materials were collected. Herbaceous plants were collected without underground organs (except for those where it was necessary to identify the species, such as Corydalis).
A plan of the surveyed area was drawn up, it shows the habitats of the species. Each species is given a brief description, photographs are taken. The results are presented in the form of herbariums and tables.
general characteristics early spring plants.
Plants need sunlight to function properly. It is in the light that photosynthesis processes take place, when organic substances are formed from inorganic substances, which are then used by plants for their development.
In the April forest, the trees and shrubs are not yet covered with foliage, nothing prevents the sunlight from penetrating to the very ground. This is the main reason that many plant species in the process of evolution have “chosen” for their development early spring.
In addition, the ground after the snow melts is saturated with moisture, which is also necessary condition for the normal development of the plant organism.
Already from the moment of snow melting in the forest community, in many plants one can observe already developed stems with young, slightly green leaves, as well as formed buds. This group of plants has another feature of development. In the second half of summer and autumn, early spring flowering plants experience a significant increase in renewal buds with the isolation of inflorescences laid in them. The growth rate of points increases as autumn approaches. During the winter months, both pollen grains and embryo sacs are formed in the flowers of early spring plants. Without exposure to low temperatures for a certain period, early spring plants do not develop. Even in those cases when the soil in the forest really freezes, the young parts of the plants do not freeze. This phenomenon is explained by the fact that the freezing temperature of cell sap in overwintering plants is much lower than 0C. In hibernating organs, starch is replaced by sugar. The sugar concentration is high, the freezing point is lower.
All early spring flowering plants are perennials, many store spare nutrients in tubers, bulbs, rhizomes, stem core for quick and early flowering.
The “transparency” of a leaf-free forest plant is also used for pollination. In a bare spring forest, nothing prevents the wind from transferring pollen from male flowers (collected in “dusty” catkins) to female flowers, consisting of only small sticky pistils. This is very typical for trees and shrubs that bloom in spring. Another interesting phenomenon for the spring forest is wind-pollinated grasses, for example, hairy sorrel. Her flowers are small, inconspicuous, but the absence of other herbs and the mass accumulation of these plants allows her to pollinate. The pollen is light and very dry.
Low-growing insect-pollinated plants attract the first insects with bright flowers. Who will notice their flowers in the dusk of a summer forest? And in the spring, when the lower tiers of the forest are well lit, yellow (anemone), blue (violets), purple (tenacious, corydalis) and pink flowers.
But the small plants allocated to the group of "ephemeroids" use all the favorable spring factors most fully.
Ephemeroids- This is a very special group of plants with peculiar habitats. In short, these are those plants which, having subterranean organs, go through their annual growing season as quickly as the ephemera. The word "ephemeral" is associated with something beautiful, but fleeting, short-lived. In our forests, their "hurried" life is associated with a sharp change luminous flux. If at the beginning of May the illumination and temperature in the forest is comparable to the illumination and temperature in open areas, then at the height of summer in the forest it is both darker and colder. This prevents not only the normal development of plants, but also the normal life of pollinators. (Biology at school. No. 1 1994 // Spring phenomena in plant life, p. 63)
An example of them could be different kinds corydalis, goose onions, anemones. They are born immediately after the snow melts. It is quite cool at this time of the year, but the ephemeroids develop very quickly nonetheless. After a week or two, they already bloom, and after another two or three weeks, their fruits with seeds already ripen. At the same time, the plants themselves turn yellow, lie down on the ground, and then their aerial part dries up.
All ephemeroids - perennials. After the aerial part dries up, they do not die. Their living underground organs are preserved in the soil: tubers, bulbs, rhizomes. These organs are repositories of reserve nutrients. It is precisely because of this building material so quickly ephemeroids develop in the spring. With such a short growing season, and even with an unfavorable spring temperature regime one cannot accumulate many nutrients necessary for the development of tall and powerful stems and large leaves. Therefore, all our ephemeroids are small in size. (Petrov V.V. Vegetable world our motherland. M: Enlightenment, 1991, p.63).
There is another problem with perennial early spring flowering plants - seed dispersal. By the time their seeds ripened, trees and shrubs were already covered with leaves, rose summer herbs. There is practically no wind in the forest, so the distribution of seeds with its help is not effective, and even animal hair cannot be reached. They also do not have time for the ripening of juicy berries that forest animals would eat. But who is always in abundance in the forest is ants. On the fruits or seeds of these plants, special fleshy appendages are formed, rich in oil - elaiosomes ( from the Greek elaion - oil, soma - body), which attract ants. Plants that spread their seeds with the help of ants are called myrmecochores. Myrmecochores include all our ephemeroids, as well as approximately 46% of all forest herbaceous plants. (Biology at school. No. 2, 1998, p. 70).
Research results
During the research work 17 species of early spring flowering plants were identified:
1. Warty birch.
2. Veronica oak.
3. Anemone is rancid.
4. Goose bow.
5. Pedunculate oak.
6. Tenacious creeping.
7. Starry oak.
8. Ash-leaved maple.
9. May lily of the valley.
10. Common hazel.
11. Mother and stepmother.
12. Hairy hairy.
13 Spring Companion.
14. Trembling poplar (aspen).
15. Dog violet.
16. Corydalis dense.
17. Common bird cherry.
Having studied the characteristics of these plants, I divided them into ecological groups 1) in relation to light; 2) in relation to moisture;
3) according to the method of pollination; 4) ephemeroids; 5) according to life forms.
By in relation to light It is customary to distinguish three main groups of plants: 1. heliophytes- (from the Greek "helios" - the sun, "phyton" - a plant) plants of open spaces, well-lit habitats; 2. facultative heliophytes- species that can live in full sunlight, but tolerate some dimming;
3. sciophytes- (from the Greek "skia" - shadow) species that do not grow in open spaces. (Life of plants, vol. 1 M: Enlightenment 1997, p. 65). These three categories of plants are, of course, not sharply demarcated. Not always the growth of plants in illuminated places (or shaded) indicates their actual need for light.
By in relation to moisture.
Plants are classified according to their ability to retain moisture.
1. Poikilohydride these plants easily absorb and easily lose water, tolerate prolonged dehydration. As a rule, these are plants with poorly developed tissues (bryophytes, ferns, algae). 2. Homoyohydrides- plants capable of maintaining a constant water content in the tissues themselves, among them there are different ecological groups (Plant Life, vol. 1, p. 76):
- hydatophytes– aquatic plants wholly or almost wholly submerged in water;
- hydrophytes- water-terrestrial, attached to the soil near water bodies and on abundantly moistened soil far from water bodies;
- hygrophytes Plants that live in well-drained soils and high humidity;
-mesophytes- plants that live with sufficient moisture;
- xerophytes- plants that can extract moisture when it is lacking, limit the evaporation of water or store water.
Ecological groups of early spring flowering plants in relation to light and moisture.
| The name of the species. | In relation to the world. | In relation to hydration. |
| Warty birch | heliophyte | mesophyte |
| Veronica oak | heliophyte | mesophyte |
| Anemone buttercup | sciophyte | mesophyte |
| goose bow | heliophyte | mesophyte |
| Pedunculate oak | heliophyte | mesophyte |
| tenacious creeping | heliophyte | mesophyte |
| chickweed oakwood | heliophyte | mesophyte |
| Ash maple | heliophyte | mesophyte |
| May lily of the valley | Facultative heliophyte | mesophyte |
| common hazel | Facultative heliophyte | mesophyte |
| Coltsfoot | heliophyte | mesophyte |
| Ojika hairy | Facultative heliophyte | mesophyte |
| Sochevichnik spring | sciophyte | mesophyte |
| Poplar trembling | heliophyte | mesophyte |
| dog violet | Facultative heliophyte | mesophyte |
| corydalis dense | heliophyte | mesophyte |
| Common bird cherry | heliophyte | mesophyte |
Analyzing the collected data presented in the table, all the early spring flowering plants that I found - mesophytes, and all these plants are heliophytes, with the exception of spring sochechnik, buttercup anemone - they sciophytes.
By pollination method
All early flowering plants are cross-pollinated by wind and insects. It is necessary to bloom early for successful pollination, especially for wind-pollinated ones, when there is still no foliage on trees and shrubs. Male inflorescences can be many times larger than female single or clustered flowers in order to produce as much fine, dry and very light pollen as possible. They say about such flowering - the plant "dusts".
Ephemeroids
Plants that quickly go through their annual growing season.
Ecological groups of early spring flowering plants according to the method of pollination and the duration of the growing season.
| The name of the species. | Pollination method. | By the length of the growing season. |
| Warty birch | Wind pollinated. | |
| Veronica oak | Insect pollinated. | |
| Anemone buttercup | Insect pollinated. | Ephemeroid |
| goose bow | Insect pollinated. | Ephemeroid |
| Pedunculate oak | Wind pollinated. | |
| tenacious creeping | Insect pollinated. | |
| chickweed oakwood | Insect pollinated. | |
| Ash maple | Wind pollinated. | |
| May lily of the valley | Insect pollinated. | |
| common hazel | Wind pollinated. | |
| Coltsfoot | Insect pollinated. | |
| Ojika hairy | Wind pollinated. | |
| Sochevichnik spring | Insect pollinated. | |
| Poplar trembling | Wind pollinated. | |
| dog violet | Insect pollinated. | |
| corydalis dense | Insect pollinated. | Ephemeroid |
| Common bird cherry | Insect pollinated. |
By life forms.
The term "life forms" was introduced in the 80s of the 19th century by the famous Danish botanist E. Warming, one of the founders of plant ecology. Warming understood the life form as “a form in which the vegetative body of a plant (individual) is in harmony with the external environment throughout its entire life, from the cradle to the coffin, from seed to death” (Life of plants, vol. 1 p. 88) . Speaking about the harmony of the plant with environment, is meant historically developed in the course of evolution the adaptability of plants to a complex of external factors that dominate in the area of its distribution.
The most popular among botanists is the classification of life forms proposed by the Danish botanist K. Rawinker (Life of Plants, vol. 1 p. 91). He singled out one sign - the location of renewal points from the surface of the earth, from which new shoots will develop:
1.Fanerophytes(Greek "Phaneros" - open, obvious) - in this type of plants, the points of renewal overwinter openly, quite high. They are protected by special bud scales. These are all trees and shrubs.
2. geophytes(Greek "geos" - earth) - renewal buds are stored in the earth. The above-ground part dies off for the winter. New shoots develop from buds located on bulbs, tubers or rhizomes wintering in the soil.
3. Hemicryptophytes(Greek "hemi" - semi-, and "crypto" - hidden) are herbaceous plants whose renewal buds are above the soil level, often under the protection of fallen leaves and other plant debris.
4. X amephites(renewal points at a height of 20-30 cm above the ground)
5. T erophytes(renewal buds in seeds). But I did not find such early spring flowering plants.
During the work, I carried out an eye count of the frequency of occurrence of species, which I displayed in the table.
| plant species | life form | Frequency of occurrence | Habitat |
| Warty birch | Fanerofit | Often | surrounding forests |
| Veronica oak | geophyte | Often | Wastelands, forest edges. |
| Anemone buttercup | geophyte | Rarely | Thickets of shrubs. |
| goose bow | geophyte | Often | Arable lands, forest edges, slopes, ditches. |
| Pedunculate oak | Fanerofit | Moderately often | surrounding forests. |
| tenacious creeping | Hemicryptophyte | moderately often | surrounding forests. |
| chickweed oakwood | geophyte | Often | Surrounding forests, edges. |
| Ash maple | Fanerofit | Rarely | Edges of the forest, settlement. |
| May lily of the valley | geophyte | Often | Surrounding forests, edges. |
| common hazel | Fanerofit | Often | Edges of the forest. |
| Coltsfoot | geophyte | Often | Ditches along roads, fields. |
| Ojika hairy | geophyte | Often | surrounding forests. |
| Sochevichnik spring | geophyte | Often | surrounding forests. |
| Poplar trembling | Fanerofit | Often | Edges of the forest. |
| dog violet | geophyte | moderately often | Surrounding forests, edges. |
| corydalis dense | geophyte | Rarely | Edges of the forest. |
| Common bird cherry | Fanerofit | moderately often | Edges of the forest. |
Findings.
Based on the study:
1. 17 species of early spring flowering plants were found.
2. Most of these plants are found moderately often and often in the vicinity of the village.
3. The main ecological groups of these plants are:
- in relation to the light - heliophytes;
- in relation to moisture - mesophytes;
- according to the method of pollination - wind-pollinated and insect-pollinated,
- according to life forms - phanerophytes, geophytes, hemicryptophytes.
4. The presence of ephemeroids was revealed.
5. Among the early spring plants, no protected ones have been identified.
Conclusion.
In the course of my research work, I did not identify rare and protected species among early spring flowering plants. But, nevertheless, they need protection. Appearing first after a long winter, they attract increased attention, which leads to a massive collection, especially those species that have beautiful flowers(corydalis, anemones, sochechniks). Explanatory work can save them from thoughtless collection, and not only among children, but also among adults. Many of the species presented in this work are medicinal. It is very important that these plants do not fall into the lists of endangered ones.
I intend to continue my work, because it seems to me that I have not met all the plants of this group yet.
The results of my work can be used by students of the 6th grade when studying the vegetation of our region in biology lessons.
List of used literature.
1. Plant life. Edited by Fedorov A.A. M: Enlightenment, 1974.
2. Petrov V.V. The flora of our Motherland. M: Enlightenment, 1991.
3. Tikhomirov V.N. Key to higher plants of the Yaroslavl region. Yaroslavl, Upper - Volga book publishing house, 1986.
4. Biology at school No. 1. 1994 // Shipunov A.B. Spring phenomena in plant life.
5. Biology at school number 2. 1998 //Klepikov M.A. Primroses.
6. Biology at school number 2. 2002 //Antsiferov A.V. Early spring field trip with sixth graders.
For science-based research, Owen Nilsson of the Swedish Plant Research Center Umeå has revealed why plants bloom with vesta.
Every morning as the sun sets over the horizon - regardless of the time of year - the clock starts ticking inside the trees.
- After a certain amount of time, plant cells begin to produce high levels molecules known as the FT protein.
- This protein is responsible for initiating the processes that help the plant grow.
- But the FT protein has a curious property: in the absence of sunlight, it stops its secretion. Therefore, when the sun goes down, the protein becomes useless for the plant.
Scientists' opinion
Scientists believe this feature is the key to the seasonality of some flowering plants, including most trees that bloom in the spring.
If a plant is genetically programmed to produce a large amount of FT protein starting, say, 13 hours after dawn, the molecule will be abundant during the last few hours of daylight on the longer days of summer. And these few hours are enough to start the critical growth processes.
As autumn progresses and the days shorten, the number of hours will vary by species and even by individual plant. The trees take this as a signal to drop their leaves and stop generating new buds.
When winter sets in, day length and temperature reach their annual minimum. At this stage, the plant goes through vernalization, a period of dormancy that is of great importance for the protection of trees.
In the spring, it can be assumed that the FT protein process is activated: the days become longer, the FT protein is produced during the daytime, and the plant begins its growth and flowering process.
If it warms up too early during the winter, the tree may take this as a sign that spring has arrived. However, when temperatures drop, as it always does at the end of winter, the tree's seeds do not germinate or grow, hindering the tree's reproductive process.
Back forward
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Lesson objectives: to introduce students to the various methods of pollination in flowering plants, to consider adaptations to various methods of pollination that arose during evolution .
Lesson objectives:
Educational: show the importance of pollination in plant life.
Developing: to form the ability to highlight the main thing, compare, systematize the features of insect-pollinated and wind-pollinated plants, continue the formation of the ability to work with a textbook.
Educational: promote the ethical education of children, instill a love of nature.
Lesson type: combined.
Teaching methods: reproductive, partially exploratory, work in pairs.
Equipment: tables "The structure of a flower", "Pollination of flowers by insects", "Wind-pollinated plants", "Artificial pollination of corn", envelopes with a task, a computer, a projector, an educational disk "Biology -6", a herbarium of self-pollinated and cross-pollinated plants, a presentation for the lesson , workbook No. 1.
During the classes
- Organizational part of the lesson.
- Updating students' knowledge.
- Exploring a new topic.
- Consolidation of new material.
- Summing up the lesson. Putting marks.
- Homework.
1. Organizational part of the lesson.
2. Actualization of students' knowledge. Checking homework.
All the life the flowers don't leave us
Beautiful heirs of nature.
They come to us at dawn,
At sunset, they carefully leave.
A) Frontal conversation on the questions:
What plants are called flowering plants?
What is a flower? What are the main parts of a flower?
What is the structure of the pistil?
What develops from the ovary of the pistil?
What is the structure of a stamen?
What is in the anther of a stamen?
What is an inflorescence
b) Work in pairs. Solving a crossword puzzle on the topic covered
(children receive crossword puzzles and start solving it).
C) Summarizing the answers (slide number 1-transition to a new topic)
3. Learning a new topic. (
slide number 2)A) goal setting
Why does the plant bloom? To please us humans?
Why are there many different insects on plants during this period?
Teacher: (slide number 3) Summarizes the students' answers and together define "bloom"
- What is pollination?
(Suggested student answers) (slide number 4)
The value of pollination (slide number 5)
Pollination types: (slide number 6)
A) self-pollination B) cross-pollination. Self-pollination.
Slide number 7. Self-pollination. Give a brief description of self-pollination. Why do you think plants need to self-pollinate?
(Suggested student responses)
What adaptations do plants have for self-pollination?
(Suggested student responses)
- often occurs in unopened flowers, that is, in a bud;
- the stamens are longer than the pistils and the pollen from them, under the influence of gravity, itself crumbles onto the pistils;
Then together we formulate a conclusion and pay attention to (slide No. 8).
Plant adaptations for self-pollination.
Slide number 9. Examples of plants in which self-pollination is observed.
Slide number 10. Cross pollination (definition). Give brief description cross pollination.
Complete task number 1 in the workbook to paragraph 24.
Cross-pollination can be of several types.
Slides number 11-12. Cross-pollination by insects.
Guys, what do you think, what adaptations do plants have for pollination by insects? (intended student responses).
Then we formulate a conclusion together.
Slides No. 13-14. Adaptations of plants to pollination by insects.
Slide number 15. Pollination of plants by wind.
Guys, what do you think, what adaptations do plants have for wind pollination?
Slide number 16. Adaptations of plants to wind pollination.
Slide number 17. Examples of plants pollinated by the wind
(Birch, hazel, oak, alder, aspen, rye, corn, wheatgrass)
To consolidate the material, complete task No. 2 in the workbook.
Then we perform the laboratory work "Consideration of insect-pollinated and wind-pollinated plants" (Instruction card on pages 90-91)
(Students work with herbarium material, then formulate a conclusion)
Questions for students:
- How can you find out from the structure of a flower how a plant is pollinated, by wind or insects?
- What signs of adaptability appeared in the process of evolution in wind-pollinated and insect-pollinated plants?
(Suggested student responses). Then we formulate a conclusion together.
There are other ways to pollinate plants.
Slide number 17. Other ways of pollinating plants.
Slide number 18. Pollination with water.
Slide number 19. Kopyten. Ants are pollinators.
Slide number 20. Hummingbird.
Slide number 21. Baobab.
Slide number 22. Animal Couscous in Australia.
Teacher. In addition to natural pollination occurring in nature, artificial pollination is also possible. Artificial pollination is pollination carried out by humans in order to breed new varieties and increase plant yields. (student's story about methods of artificial pollination using a table
"Artificial pollination of corn"
4. Consolidation of new material
A) independent work (fill in the table). If the named feature is characteristic of this group of plants, a "+" sign is put, if not "-"
signs |
insect pollinated plants |
wind pollinated plants |
| 1.Large bright flowers | ||
| 2. Small bright flowers collected in inflorescences | ||
| 3. Presence of nectar | ||
| 4. Small inconspicuous flowers, often collected in inflorescences | ||
| 5. The presence of aroma | ||
| 6. Pollen is small, dry, light, large amount. | ||
| 7.Large sticky rough pollen | ||
| 8. Grow in large clusters, forming thickets | ||
| 9. Plants bloom in spring before the leaves open. | ||
| Flowers lack nectar |
B) Find biological errors. Now let's check how much you understood the topic studied. Our school received 2 letters from residents of the Flower City. You probably all remember one of the residents of the city - Dunno, who was invented by the writer Nosov. Dunno seriously decided to take up botany, but, as usual, got everything mixed up. Help him.
1 competition "Compositions of Dunno"
Your task is to find biological errors in Dunno's poems.
1. There was a birch in the field
And her bee pollinated
(Birch is pollinated by the wind)
2. As in our garden
Blooming sweet peas
Flies, bees will fly,
Let's wait for the harvest
(Pea is a self-pollinating plant)
2 competition "Why". The second letter from Znayka. He also asks you to answer questions that differ from Znayka's questions in their seriousness and correctness.
- Why do plants that bloom in the evening and at night more often have corollas of white and yellow color?
- Why can calm weather during flowering cause a decrease in rye yields, but such weather does not affect the wheat yield?
- Why in the spring, few people notice the flowering of birch.
- Why did one of the two flowers of an apple tree form a fruit, while the other did not? Why did it happen?
Wind pollinated plants are plants that are pollinated by the wind, however, under various circumstances, they can also be pollinated by insects. Wind pollinated plants have very small and numerous flowers. Such plants produce a lot of pollen: one plant is capable of producing millions of pollen grains. In many wind-pollinated plants (hazel, aspen, alder, mulberry), flowers appear even before the leaves bloom.
Wind pollinated plants. Plants whose flowers are pollinated by the wind are called wind-pollinated. Usually their inconspicuous flowers are collected in compact inflorescences, for example, in a complex spike, or in panicles. They produce a huge amount of small, light pollen. Wind pollinated plants often grow in large groups. Among them there are herbs (timothy, bluegrass, sedge), and shrubs, and trees (hazel, alder, oak, poplar, birch). Moreover, these trees and shrubs bloom at the same time as the leaves bloom (or even earlier).
In wind-pollinated plants, the stamens usually have a long filament and carry the anther outside the flower. The stigmas of the pistils are also long, "shaggy" - to catch dust particles flying in the air. These plants also have certain adaptations to ensure that pollen is not wasted, but rather falls on the stigmas of flowers of its own species. Many of them bloom by the hour: some bloom early in the morning, others in the afternoon.
Wind-pollinated plants have the following characteristics:
- inconspicuous small flowers, often collected in inflorescences, but small, inconspicuous;
- feathery stigmas and anthers on long hanging threads;
- very small, light, dry pollen.
Examples of wind pollinated plants: poplar, alder, oak, birch, hazel, rye, corn. Wind-pollinated trees usually bloom in the spring, before the leaves develop, which would interfere with the transport of pollen.
Wind-pollinated plants include oaks and beeches, alder and birch, poplars and plane trees, Walnut and hazel. In addition to trees, many herbs that usually live in large communities are pollinated by the wind: cereals, rushes, sedges, hemp, hops, nettles and plantain. This list contains only examples, it does not at all pretend to be a complete list of names of wind-pollinated plants.
The first striking feature of flowers pollinated by the wind is the absence of bright color and aroma, the absence of nectar. On the contrary, pollen grains develop in great abundance. At the same time, they are extremely small: in wind-pollinated plants, a single speck of dust has a mass of 0.000001 mg. For comparison, we can recall that in a pumpkin pollinated by bees, a speck of dust is a thousand times heavier: its mass is 0.001 mg. One inflorescence of rye is capable of producing 4 million 200 thousand pollen grains, and the inflorescence of horse chestnut is even ten times more - 42 million. Feature pollen grains of wind-pollinated flowers is that they are completely devoid of gluing substances and in most cases have a smooth surface.
Despite the fact that the wind-pollinated flowers are devoid of nectar, they are often visited by insects that feed on pollen. However, as pollen carriers, these insects play almost no role.
The spread of pollen that the plant “throws into the wind” is, of course, an uncontrollable process. And the probability that pollen grains will fall on the stigma of their own flower is very high. But, as we know, self-pollination is undesirable for a plant. Therefore, wind-pollinated flowers have widely developed adaptations that prevent it. Especially frequent is the non-simultaneous maturation of anthers and stigmas. In many wind-pollinated plants, for the same reason, probably, the flowers are dioecious, and sometimes even two-domed.
Most wind-pollinated woody plants flower in early spring, before the leaves appear. This is especially evident in birch, in hazel. After all, it is clear that dense summer foliage would be a very formidable obstacle to pollen flying in the wind.
There are some other adaptations for wind pollination. In many cereals, the stamens, when the flower opens, begin to grow unusually rapidly, lengthening every minute by 1–1.5 mm. In a short time, their length is 3-4 times greater than the original, they grow beyond the flower and hang down. And only when the anthers are at the bottom, they begin to crack, and the anther here is somewhat bent and forms a kind of tray or bowl where the pollen is poured. Thus, she does not fall down to the ground, but waits for the next gust of wind to fly on his wings.
It is interesting that the pedicels in the spikelets of some cereals seem to spread apart by the beginning of flowering, forming an angle of 45–80 ° between them. This also contributes to the blowing of pollen by the wind. As soon as flowering ends, pollinated flowers return to their place.
During flowering, the position of the entire inflorescence also changes in birch, poplar, and hornbeam. At first, the inflorescences are directed upwards. But before the anthers begin to burst, the stem of the earring is pulled out and the inflorescence hangs down. Each flower thus becomes separated from the other and accessible to the wind. Pollen falls from the anthers down onto the scale of the lower flower and is blown away by the wind from here.
Wind-pollinated plants also have an "explosive" type of flower, similar to that of insect-pollinated ones. Thus, the stamens of a flower of one of the nettle species, ripening in a bud, are so tense that when it opens, they sharply straighten and scatter pollen from bursting anthers. At this moment, a thick cloud of pollen can be seen above the flower.
The pollen of wind-pollinated flowers is by no means scattered by them at any time of the day or night, but only in favorable weather, usually relatively dry, with light or medium wind. Most often, the most suitable for pollination are the morning hours.
Comparison of insect pollinated and wind pollinated plants
|
flower signs |
insect pollinated plants |
wind pollinated plants |
| Inconspicuous or missing | ||
|
2. Location of stamens |
inside a flower |
Open, anthers on long threads |
|
3. Stigmas of pistils |
small |
Large, often pinnate |
| Not very much, sticky, large | Very many, dry, shallow | |
|
Many have |
||
|
Many have |
