Why does cross-pollination predominate in nature? About why cross-subsidization has become a problem not only for the electric power industry. Types of cross pollination
Many people know that cross-pollination is one of the most common ways of plant propagation. But information about why most plants chose this particular method, as well as about the different types, is not so common.
What it is
Pollination is the process of transferring pollen from the anthers to the ovule (common among gymnosperms) or the stigma of the pistil (inherent in angiosperms). As a result of this, the female organ - the kidney or ovule - begins to develop, transforming into a fetus.
The two most common types of pollination are self-pollination and cross-pollination. The first option is less common. In this case, pollen falls from the anther to the pistil of the same flower, often even before its petals open. On the one hand, it is much more reliable - the number of empty flowers in this case tends to zero.
Cross-pollination is the process of transferring pollen from the anther of one flower to the pistil of another. And this variant, despite the great complexity, is found among plants much more often - in almost 90 percent of higher plants. Why is cross-pollination common in nature?
Types of cross pollination
To date, experts have identified two types of cross-pollination in plants - xenogamy and geitonogamy.
Geitonogamy is the process of pollination, which involves the stamens and pistil of different flowers located on the same plant. That is, the tree is quite capable of independently pollinating and producing fruits even in the absence of relatives nearby.
Therefore, specialists have long been arguing about whether this is cross-pollination or, rather, a special way of self-pollination takes place. The fact is that the exchange of genetic material does not occur here, namely, it is the main goal of cross-pollination.
But xenogamy is a completely different matter. The process is exactly the same, but it must involve flowers located on different plants. In order to protect themselves from accidental pollination of flowers on the same plant, some species have even developed a protective mechanism - the separation of the sexes. At the same time, in the flowers of one plant there are only pistils, and on the other - only stamens. Therefore, the possibility of self-pollination is completely excluded.
Who helps pollination
Of course, the main assistant in cross-pollination is insects, primarily bees. Here zoophilia takes place - this is the term used to call any pollination of plants performed with the help of representatives of the animal world.
Two rather rare subspecies can be distinguished here:
- myrmecophilia, when pollination is carried out exclusively by ants;
- cantharophilia - here beetles act as the main pollinators.
But this is found only in relic plants that have survived to this day.
Another case of bestiality is ornithophilia - pollination by birds. Such a cross is not very common - it is found mainly in the tropical zones of America, because the only birds that contribute to pollination are hummingbirds.
Finally, chiropterophilia is quite common - pollination by bats. And plants using this method are also common only in warm countries, mainly in the jungle. Bats, licking sweet nectar from flowers, carry pollen on their tongues and coats.
Less common are anemophily (pollination by wind) and hydrophilia (here pollen is transferred from flower to flower by water - found in some gymnosperms and algae).
Now it is clear that pollination can be carried out by a variety of methods. But which one is the most common?
The prevalence of different methods of pollination
The vast majority of plants that cross-pollinate do so through bestiality. Yes, it is insects, birds or mammals that pollinate almost 80 percent of higher plants.
Significantly behind the leader is anemophilia. No more than 20 percent of plants use the wind to carry pollen.
But the least common is hydrophilia. Fewer than 1 percent of all plants rely on water streams to carry their pollen, either in ponds or after rain.
Main advantages
It is worth understanding why cross-pollination is so widespread.
As noted above, the number of barren flowers is almost completely absent in plants using self-pollination. But at the same time, it was cross-pollination that turned out to be more viable - this proves the abundance of such plants.
In fact, everything is simple here. In self-pollination (as in geitonogamy), the plant reproduces by itself. Only the genetic material that it has is used, and, as it turned out, this is a losing strategy.
Indeed, with xenogamy, plants that grow from seeds obtained by crossing two plants receive the advantages and characteristics of both parents. That is, if one tree grew on dry soil and managed to adapt to it, and the other, on the contrary, grew in a swamp and survived, then the new tree that became their offspring will equally easily adapt to both the lack of moisture and its excess. Consequently, the likelihood that it will die in adverse conditions is drastically reduced.
It is thanks to this that plants with cross-pollination began to dominate throughout the world, confidently displacing competitors that appeared on Earth millions of years earlier.
Ways to Attract Pollinators
It was noted above that four out of five plants are used for pollination by animals - from mammals to insects. Of course, at the same time, they developed an appropriate mechanism for luring them.
The most common is the presence of sweet nectar. Many millions of years ago, in an effort to lure pollinators to themselves, some plants acquired cells that could secrete a sweet substance. The experience was successful, and as a result, he had many thousands of descendants who produced nectar with a pungent odor. Such plants, first of all, are guided by animals and insects with a delicate sense of smell.
But there are also plants that use ornithophily. And birds, as you know, are almost devoid of smell. A different technique was used here - larger and brighter flowers that almost do not smell. They perfectly lure hummingbirds, who know that sweet nectar is waiting for them inside.
Conclusion
From this article it becomes clear what cross-pollination is, as well as what are the main advantages of this method. And at the same time, the article provides information about different methods of pollination with the involvement of various forces from the outside. This will allow you to understand botany much better and pass for a person with the broadest outlook.
1. What is a flower?
A flower is a modified shortened shoot that serves for seed reproduction.
2. What structure does it have?
The pistil and stamens are the main parts of a flower. Perianth is located around the stamens and pistil. The perianth consists of two types of leaflets. The inner leaflets are the petals that make up the corolla. The outer leaves - sepals - form a calyx. The thin stalk, on which a flower sits in most plants, is called a pedicel, and its upper, expanded part, which can take on various shapes, is called a receptacle.
3. What is the structure of a stamen?
The stamen has an anther inside which the pollen matures. The anther is located on the filament.
4. What is the structure of the pistil?
The pistil has a stigma, style and ovary.
5. What is called an inflorescence?
Inflorescences are groups of flowers located close to each other in a certain order.
6. What process is called fertilization?
The process of fusion of male and female gametes is called fertilization.
Questions
1. Why is fertilization called double in flowering plants?
Fertilization in flowering plants is called double, because. two spermatozoa penetrate the ovary of angiosperms, one of them merges with the egg, giving rise to a diploid embryo, the other unites with the central diploid cell.
2. How is a plant embryo formed?
Two spermatozoa penetrate into the ovary of angiosperms. One of the sperm fuses with the egg. The zygote formed by the fusion of gametes divides into two cells. Each of the resulting cells divides again, and so on. As a result of multiple cell divisions, a multicellular embryo of a new plant develops.
3. As a result of what process, occurring in the ovary, endosperm is formed?
The second sperm fuses with the secondary nucleus located in the center of the embryo sac, which leads to the formation of a triploid nucleus near the central cell. It divides, forming endosperm cells, in which nutrient reserves accumulate.
4. What does the seed coat develop from?
The seed coat of seeds in flowering plants is formed from the integument of the ovule.
5. What methods of pollination do you know?
There are two main types of pollination: self-pollination and cross-pollination. During self-pollination, pollen from a stamen falls on the stigma of the pistil of the same flower. In cross-pollination, pollen from the stamens of a flower of one plant is transferred to the stigmas of the pistils of flowers of other plants.
Also, depending on who acts as a pollinator, natural (in nature) and artificial pollination are distinguished. In artificial pollination, a person acts as a pollinator. At the same time, he sometimes deliberately transfers pollen from the stamens to the stigmas of the pistils.
6. What is the purpose of artificial pollination?
Artificial pollination is carried out in order to develop new varieties and increase the yield of some plants.
Think
Why is cross-pollination much more common in nature than self-pollination?
With cross-pollination, the recombination of hereditary traits of the paternal and maternal organisms occurs, and the resulting offspring can acquire new properties that the parents did not have. Such offspring are more viable.
Tasks
After analyzing the text of § 24 and figure 102, explain what the structural features of the pollen grain shell are connected with.
The structural features of the pollen grain shell are due to the way it is transferred from stamens to pistils.
In wind-pollinated plants, it is dry, devoid of sculpture, mostly has pores, and is produced in large quantities.
The pollen of insect pollinated plants is larger or very small, sticky, has a sculpture and a large number of apertures.
Tasks
1. Study additional text. Identify the similarities and differences between wind pollinated and insect pollinated plants.
Similarity: the abundance of pollen in the flower and the presence of inflorescences (in any case, this increases the chances of pollination).
Signs that are characteristic only for insect-pollinated plants:
Large single flowers, bright color of petals or tepals of a simple perianth, the presence of nectar and aroma.
Large, sticky, rough pollen of flowers (adheres well to the hairy body of the insect).
Signs that are characteristic only for wind-pollinated plants:
There are no bright, large and fragrant flowers. Inconspicuous, usually small flowers, feathery stigmas, anthers on long hanging threads.
Very small, light, dry pollen (adaptations for wind pollination).
2. Observe the flowering plants in the school area. Determine which of them are wind pollinated and which are insect pollinated.
Wind pollinated: birch, oak, aspen, alder.
Insect pollinators: clover, dandelion, rose, linden, apple tree.
Quests for the curious
Analyze Figure 105. Draw a conclusion and discuss it in class.
In lower plants, the gametophyte reaches the greatest development, but as the plants become more complex, the gametophyte is suppressed and the sporophyte becomes the predominant form. The greatest reduction of the gametophyte is observed in seed plants. It is striking that both among the lower and higher plants, all large and complex organisms are sporophytes.
Reasons: change of habitat to land-air, which is less stable. Diploid organisms are highly resistant. Recessive mutations persist in the heterozygous state.
Payment of the expenses of some electricity consumers at the expense of others is one of the main problems in the development of the electric power industry in Russia. Such a system developed in the 1990s and was of an exclusively socio-political nature, when, in the wake of upheavals in the economy, the authorities did not want extra reasons for riots. In recent years, market participants and experts have repeatedly approached the issue of abolishing cross-subsidization or at least changing the system, and in the face of the need for a "spurt" of the economy and the task of increasing GDP growth rates above the global ones, the discussion has escalated.
“Crossroads is probably one of the main problems that has developed over the course of more than two decades. If we take the Soviet experience of supplying electricity in the interests of industry and in the interests of the population, then the price parity in 1982 was 3.5 times: prices for industry are 3.5 times higher than for the population, ”he said last week at a round table "to the chairman of the Duma Committee on Energy Pavel. In 1992, this figure fell to one and a half times, and now the tariffs for the population are lower - a coefficient of 0.8. At the same time, several types of cross-subsidization have developed in Russia - price containment in a number of regions (in particular, in the Far East), support for renewable energy sources, and preservation of non-market tariffs for citizens. The result of the latter: tariffs for legal entities are growing at an accelerated pace, including budget organizations (and here there are "holes" in the budgets), small and medium-sized businesses and agricultural producers, says Zavalny.
Moreover, estimates of the volume of cross-subsidizing vary, including those of the authorities. The deputy gave an estimate of 380 billion rubles. According to the calculations of the Institute for Problems of Pricing and Regulation of Natural Monopolies, this is about 280 billion rubles. for 2016, and now - about 300 billion, its director told Gazeta.Ru.
“The total volume of intersections between consumer groups today exceeds 220 billion rubles, and if the measures to reduce it, planned by the government a few years ago, are not implemented, this figure may double in the next 5 years,” believes Vygon Consulting’s Director of Power Industry Alexey Zhikharev.
Accordingly, this system diverts funds from companies. And generally non-market, points out Dolmatov. “It is probably reasonable to proceed from the fact that, of course, this is a wrong situation that needs to be corrected,” he believes, calling the proposals of some enterprises reasonable.
An oasis of cheapness
At the same time, tariff decisions for the population are made by the constituent entities of the Russian Federation, and the tariffs themselves vary from region to region. The highest are in Chukotka and Kamchatka. The Irkutsk region stands apart, where the tariff is only 1.01 rubles. (from July 1 it will be increased to 1.06 rubles). For a long time, the authorities of the region take credit for low energy tariffs, there were periods when they did not change for years (for example, under Governor Boris Govorin).
“The Irkutsk region is a vivid example of tariff distortions, the volume of “crossroads” here is close to 3 billion rubles, which is how much industrialists overpay. To what extent such benefits are justified is a question,” says Alexey Zhikharev from Vygon Consulting.
It is for the Irkutsk region, which combines assets, proposed to cancel the crossroads. The Irkutsk and Bratsk aluminum smelters operate in the region, which, due to US sanctions, are in a difficult situation. “The consumption of enterprises is about 40% in the balance of demand in the price zone of Siberia, therefore, a reduction in the output of finished products or the closure of aluminum plants will greatly reduce the volume of electricity consumption in Siberia, which will form the risks of operating the Siberian energy system in extreme modes: “idle” discharges of water from hydroelectric power plants and the operation of thermal power plants at minimum possible load," the company said.
The NP Market Council supported the proposal to reduce cross-subsidization in the Irkutsk region, the head of the NP said earlier. As Kommersant reported, they supported the reduction of "crossroads" in the Irkutsk region. The Ministry of Energy has not yet developed a position. “Indeed, it received a corresponding instruction, it is still in work,” Gazeta.Ru was told in the press service of the Ministry of Energy.
The governor, who represents , expectedly spoke out against the repeal. The reason is the soreness, in his opinion, of this issue for the population.
At the same time, electricity tariffs for the urban population in the Irkutsk region are the lowest in Russia: 1.01 rubles. per kWh (single rate tariff) with an average per capita income of 22.4 thousand rubles. in 2017. For comparison: the average Russian tariff is 4.3 rubles / kWh with an average per capita income of 31.5 thousand, and in the Krasnoyarsk Territory, which is similar in climatic conditions, it is 3.78 rubles / kWh with an average per capita income of 28 thousand rubles. Compared to some regions, the difference is even higher: for example, residents of the Altai Republic are poorer, but pay more - 4.81 rubles. with an average per capita income of 19 thousand rubles. The lowest per capita income in Siberia, according to Rosstat, is in Tuva (13.8 thousand rubles). But even there the tariff is more than 3 times higher than in Irkutsk.
If we start from the consumption norms approved in the Irkutsk region, then the monthly payment of an Irkutsk family of four living in a three-room apartment with an electric stove (95 kWh per person in 2017), then the payment is about 384 rubles. For the same consumption of electricity, a family from the Altai Republic will pay 1,790 rubles, in the Krasnoyarsk Territory - 1,436 rubles. The difference is many times.
The process of setting tariffs for electricity and utilities for the population is strictly regulated by federal law, the administration of the Irkutsk region said. If the payment (total, not only for electricity) grows more, then the regional authorities must compensate for the difference from the budget. “Accordingly, the region understands that this will be an additional burden for it, and, of course, does not seek to increase tariffs for the population ... The first is because they do not want to compensate, and the second is, of course, the region does not yet see incentives for itself, which it will bring political benefits,” explains Ilya Dolmatov.
Tough social policy also prevents the introduction of social norms, adds. “The issue of introducing such a concept as a social norm into tariff regulation, which implies maintaining a low level of tariff for the population only within a certain limit, was initiated more than 10 years ago during the reform of RAO UES of Russia, but a tough social policy opposes its development,” the expert points out. According to him, the mining of bitcoins by citizens in their apartments can also add problems.
“Judging by the fact that the press is full of information about the growing network of Siberian miners, cheap electricity has become a magnet for them, so we are already facing multi-level cross-subsidization. As far as we know, the issue of regulating mining with the parallel implementation of monitoring systems for such activities is already being considered by the government and the Central Bank,” Zhikharev added.
Reform of the cross-subsidization system is needed, experts say. But it is necessary to gradually abolish this system throughout the country.
“It is clear that it is rather difficult to correct the situation at once. But to say that this is a normal situation and that it does not need to be changed is obviously also wrong, because the consumer, including Rusal, rightly declares that they bear an unreasonable additional tariff burden, ”Ilya Dolmatov points out. According to Alexander Zhikharev, the issue should be resolved gradually - over 5-7 years. “But even such a horizon will not allow setting tariffs for the population on the principle of “inflation minus”, in regions such as the Irkutsk region, growth rates should be above 20%,” the expert states.
105. Let us explain where the name of double fertilization in flowering plants comes from.
In flowering plants, two fusions occur during fertilization: the first sperm fuses with the egg and a zygote is formed, the second with a large central cell and endosperm is formed.
106. Let's sign the elements of the development cycle of a flowering plant, indicated in the figure by numbers.
1. mature plant
2. flower
3. pollen grain
4. ovary
5. ripening fruit
6. ripe fruit with seeds
7. seed
8. young plant.
107. Let's combine the parts of the flower with the fruits formed from them.
108. Let's write the pollination methods indicated in the figure.
1. Self-pollination.
2. cross pollination.
109. Let us explain why cross-pollination is more common than self-pollination.
Cross-pollination provides a variety of traits in offspring, as different organisms reproduce, and not one (as in self-pollination). This is more beneficial in terms of evolution. That is why in nature numerous mechanisms have been developed in plants that prevent self-pollination. There are also a large number of pollen carriers (animals, wind, humans).
110. Fill in the table.
111. Distribute wind-pollinated and insect-pollinated plants.
Wind pollinated: birch, oak, hazel, rye, corn, alder.
Insect pollinators: linden, apple tree, clover, wild rose, fragrant tobacco, snapdragon.
112. Denote the sequence of actions during artificial pollination.
