Distribution of fruits and seeds - Knowledge Hypermarket. Methods of seed dispersal How plants spread

Plants strive to reproduce in all imaginable and inconceivable ways, however, it is worth remembering that not only seeds are important for the further spread of plants in a given area. Very important For cultivated plants It has environment and climatic conditions. Only in the presence of heat, moisture and oxygen can the plant develop. If at least one of these components is missing, the plant dies. So let's look at how seeds spread.

Methods of seed dispersal

It is for this reason that many seeds strive to get into a climate acceptable to them as quickly as possible. Biology knows of at least eight ways of spreading seeds of cultivated plants. Let's look at each way plant seeds spread.

• The first method of seed dispersal is its external adaptability and readiness for it to be transported over a long distance. For example, great amount seeds have devices such as spikes or hooks, with the help of which they can be attached to human clothing or animal fur and transferred over distances.
• The second type of seeds are sticky ones. They are located in the rather sticky berries of plants. Such berries are eaten by birds, and when they begin to peck at them, the seeds are attached to the feathers and travel very long distances on the bird.
• In addition, another not entirely known the usual way how fruits and seeds are distributed. It lies in the fact that such plants grow near bodies of water or even in water. The seeds are mixed with mud or water and then transferred on the paws of animals or on people's shoes. Also, such seeds can stick to the paws of birds with dirt.
• In addition, there are plants that are eaten by animals. While they are eating the delicious filling, they do not think about the fact that along with this there are a lot of seeds stuck to their mouth, and when they fly away to travel, the seeds are carried over long distances along with them.
• However, we should not downplay the human influence on the spread of wild plant seeds across the earth. We carry thousands of plants on our clothes without even knowing it. For example, when we collect very small seeds, we often weed out those that are not suitable in size or for some other reason. It is attached to our shoes or clothes and transported to distant lands.
• However, seeds can be scattered on the ground and by the wind. The seeds thus spread through the air quite independently. These are various fluffy devices that help the seed control its flight. Some seeds even have small wings or parachute-like devices.
• The next category of seeds that spread independently are the so-called “swimmers”. They move around a body of water with the help of the river current.
• There is also a special category of plants that explode in order to spread their seeds over distances. After full ripening occurs, the fruits of the plants dry out and burst, throwing out the seeds over a considerable radius.

Thus, plants spread not only with the help of living beings, but also independently.

After seed formation, either the entire fruit or the seed (or seed) it contains is separated from the parent plant. The methods of dispersal of seeds and fruits in flowering plants are very diverse. Of course, wind and water are widely used here as intermediaries in dispersal, but to them is also added the mediation of animals, as well as the use of mechanical forces arising in the plant itself, and, in addition, numerous adaptations of the fruit that allow the most effective use of these intermediaries.

There are three main external factors spreading seeds

1) spread by wind (anemochoria);

2) distribution by animals (zoochory);

3) distribution by water (hydrochoria).

Distribution by animals

Animal seed dispersal is generally more reliable, as animals tend to visit fertile areas suitable for seed germination. The fruits, equipped with spines or hooks, cling to the skin or fur of passing animals and can be carried some distance before being picked off or falling off. Trailers develop from different parts fetus or surrounding structures .

Rice. 1. Fruits distributed by animals

Examples are the fruits of bedstraw, gravilat, burdock, carrots, buttercup, string, and agrimony.

Examples of juicy fruits are plums, blackberries, strawberries, tomatoes, and apples. The fleshy parts of these fruits serve as food for animals and birds. When ripe, they usually acquire bright colors and aroma that attract animals. The animal eats it and the seeds pass through the intestines and are excreted, often landing on fertile soil. Contained in excrement nutrients can increase the fertility of the soil around the seed.

Wind propagation

Many wind-dispersed plants have special devices. These include volatiles, which are supplied, for example, with the seeds of willow, fireweed, cotton, dandelion fruits, and lionfish, such as pine (gymnosperms), ulcer, ash, maple, hornbeam.

Rice. 2. Fruits and seeds distributed by the wind

In a number of plants, for example, poppy, nigella, foxglove, lychnis, the fruit is a capsule sitting on a stalk, which is swayed by the wind, so that numerous small seeds spill out through the pores in the upper part of the fruit.

The seeds of some plants, for example, orchids, are so small and light that they are carried by the wind, without any special appendages or dehiscent fruits. Their opening occurs by cracking along the seam between the carpels, as, for example, in beans. In this case, the seeds are either thrown out of the fruits with a more or less strong push, or simply fall out of them. Some of these seeds have adaptations for dispersal by wind (for example, fireweed). The capsules can also be dehiscent (for example, poppy and fireweed), and in some plants the seeds are thrown out of them with force (for example, violets).

Spread by water

Substances such as proteins, starch, sugars, fatty oils, some vitamins, etc. accumulate in the cells of the ovary wall. Only a few

fruits and seeds are specially adapted for dispersal by water. They contain air cavities that hold them on the surface of the water.

Rice. 3. Fruits spread by water

The coconut is a drupe with a fibrous mesocarp and numerous air-bearing cavities. In the water lily, the seed is equipped with a spongy shell derived from the stalk of the ovule.

Random distribution

The division of seeds and fruits into categories depending on their mode of distribution is not strict. In many cases, the element of chance plays a large role, and a given fruit or seed can spread in two of these three ways, or even in all three. One of the main factors in accidental spread is humans; seeds may cling or stick to his clothing, etc., or be transported with various loads on vehicles. Contamination of grain crops by weed seeds is a common phenomenon observed throughout the globe. Nuts stored away by rodents may remain and germinate next spring. Floods, hurricanes, etc. can carry seeds further than usual.

Seeds are quite rare, but germinate directly in the plant. For example, cutting into a ripe pumpkin, we can observe already sprouted seeds in it. However, they generally germinate not where they ripen, but in a completely different place. What are they - methods of dispersal of fruits and seeds of plants? How does this happen and why? Let's find out!

What is a fruit

Before we look in detail at the methods of dispersing fruits and seeds, we should study these very concepts. After all, without basic knowledge it will be difficult for us to understand the whole process and mechanism of the “travel” of seeds and fruits around the world. So, let's begin. It is no secret that pear, plum, apple, strawberry, cherry are the fruits of fruit plants and trees containing seeds. It is believed that they develop from ovaries and other parts of plants, but not all botanists agree with this.

Some of them are sure that only those that are formed exclusively on the ovaries can be called real fruits, for example, cherries, plums, tomatoes, poppy seeds, etc. Fruits that develop from other parts of flowers and plants are usually called false. For example, strawberries are generally formed by an overgrown receptacle. What kind of ovary can we even talk about here! As a result, scientists decided to consider the fruits as the result of modification of the entire flower. Moreover, if at the beginning of its “ life path“They can still somehow retain some characteristics of the flower, but after ripening they completely lose or greatly modify them.

How do plant fruits work?

On the outside, each fruit is surrounded by a so-called pericarp, which protects the seeds ripening inside from damage and drying out. In turn, the pericarp is divided into juicy and dry. For example, juicy pericarp can be called pulp ripe watermelon, melon or peach. The unripe pericarp is astringent, bitter, sour, and tasteless. During this period, it protects the fruit itself from untimely eating, and its still immature seeds from rapid spoilage.

Types of fruits

To understand how the seeds and fruits of certain plants and trees spread, you need to know that botany refers to juicy fruits as:

• multi-seeded (pumpkin, berry, apple, pomegranate);
• single-seeded (peach, apricot, mango, cherry, bird cherry, prune).

As the name of the fruit suggests, single-seeded fruits have one seed. They are also called drupes. However, there is an exception here: for example, the blackberry is a polydrupe, but is a single-seeded fruit.

The methods of distribution of fruits and seeds directly depend on their size, weight and shape. As mentioned above, the fruits can be juicy and dry. Dry ones, in turn, are divided into dehiscent and non-dehiscent. For example, the pericarps of ripe beans, pods, and poppy pods open (burst) after they ripen. But, for example, the hazel pericarp is very hard and woody. There's no way in hell he'll open himself up. It has one single seed that we know very well: the nut.

Another type of fruit is the capsule. Usually it has from 3 to 5 nests with seeds. When these seeds ripen, their “house” begins to burst. For example, boxes of St. John's wort or tobacco develop cracks along their partitions, after which they fall apart into separate parts. At the same time, only the walls of the “houses” of lilies, hyacinths, tulips and cotton plants are cracking, while the boxes of poplar and willow are generally bursting at the seams. The most famous capsule is the pod, which, during ripening, splits into two leaves with a bang.

Is a berry considered a fruit?

Yes. This is a kind of fruit that contains many seeds, but does not have seeds. If the berry is ripe, then it has a juicy and fleshy pericarp (grapes, strawberries, lingonberries, cranberries, blueberries). That is why, from the point of view of botanical scientists, cherries are not a berry, but tomatoes are! This also includes citrus fruits, which are also berries:

• tangerines;
• oranges;
• lemons;
• Pomeranians;
• grapefruits.

The fact is that the nests with seeds located inside the above-mentioned fruits are filled with aromatic exotic juice. The following fruits can also be called berries:

• melons;
• watermelons;
• cucumbers

This, of course, hurts the ears of the common man, but professional botanists have long become accustomed to the idea that formally, watermelon and cucumber are not only berries, but also relatives.

What does a seed look like from the inside?

Distribution of fruits and seeds (grade 2, introduction in biology lessons to students of certain methods of “travel” of seeds and fruits various plants) is unthinkable without the participation of humans, animals and, of course, water and wind. But to understand how such a small seed can “travel” around the world, you need to briefly familiarize yourself with its structure. So, any seed is covered with a skin. On smooth seeds, a scar is visible, forming in those places where it is separated from the seed stalk.

If you look closely, next to such a scar you can see a micropolar opening, scientifically called a micropyle. There is also a root tip somewhere nearby. It is he who emerges first when the seed germinates. The dense peel protects the seed from various damage and at the same time allows moisture to pass through without interfering with the germination of the embryo - the main part of all seeds. It is formed only after fertilization of the egg and usually consists of a stem, root and bud.

How are plant seeds distributed in nature?

Well, here we come to the main thing. As mentioned above, rarely germinated seeds give birth to new plants, since in the vast majority of cases they do not grow in the place where they ripened. Why is this happening? It's simple: they “travel” to new places through people, animals and Mother Nature herself! If the conditions for new life turn out to be quite suitable, these seeds will begin to germinate, and if not, they will die.

1. An excellent way to spread them is through cross-breeding, which can create new species of flora representatives. This is the minimum that gives life to new plants. Of course, the methods of dispersal of fruits and seeds of plants are not limited to pollination.
2. Unpleasant to human taste or not at all poisonous fruits and the seeds are very attractive food for birds. At the same time, seeds that have a hard shell are simply not able to be digested in their stomachs. As a result, they, together with bird droppings (guano), are transported over long distances from the place of their original “birth”. But the role of birds in the spread of new plant life is not limited to this!
3. Many birds, arranging supplies for the winter, carry seeds and fruits of various plants into their nests. Some of them are simply lost during bird flights, falling to new places. For example, they constantly stock up on acorns, some of which are lost and germinate over time.
4. Another helper in the germination of seeds and fruits are ants. These small but useful creatures in nature carry the seeds of the most beautiful things into their nests. different plants, especially the rich essential oils(cornflower, celandine, lungwort, oxalis, violet). Like birds, ants the lion's share collected seeds are lost along the way. By the way, these little sneaks mainly have access to grass seeds.

How else do fruits and seeds of plants “travel”?

They are mainly spread by wind. In this case, the seeds scatter much better than already formed fruits. But more on that later. As you know, in nature there are so-called “live” fruits that independently cling to the fur of animals that accidentally run past, and also stick to human clothing. For example, these are the fruits of burdock, string, cocklebur and burdock.

Here, botanists especially note Pisonia - a shrub or tree growing on the islands Pacific Ocean. The fruit of this is enclosed in a special cup, seated with rows of various sticky hairs. They allow pisonia fruits to easily stick to any animal or object. Often in nature you can see reptiles and small birds, completely covered with such fruits. Unfortunately, in this case, the animals cannot fully move and die.

"Travel" by air

You know that fruits and seeds can be spread by wind, i.e. by air? For example, this happens in high mountain steppes, savannas and deserts, where strong winds constantly blow. In this case, the seeds simply scatter into different sides and over vast distances. It is especially good for seeds that have flat shape and small sizes (bell, hop, heather, broomrape, eucalyptus).

Winged seeds and fruits

It will be interesting to find out how seeds that have so-called wings are spread by the wind. They appeared in those plants that grow exclusively in open areas. These “wings” are specific hairs that completely cover the seeds (for example, in anemone). In poplars and willows, the seeds are generally equipped with tufts consisting of the finest hairs.

Hazel, hornbeam, alder and birch fruits are small nuts equipped with wings. The fruits of ash and maple trees have one wing each. By the way, this is why they spin when they fall. The seeds and fruits of sedge, bladderwort, and astragalus are spread by the wind. It is curious that in these plants they travel to balloons, which are formed with the help of air sacs covering them.

Tumbleweed

Probably everyone has heard about such a bizarre plant at least once. Its scientific name is kachim paniculata. IN autumn time it tends to break away completely from its root. Loose and spherical bushes of this plant with ripe fruits spread with the help of the wind. The seeds of Kachim paniculata are hidden in boxes, the teeth of which are curved inwards. This allows the seeds to spill out only during fairly strong gusts of wind, carrying them over long distances.

"Journey" on water

Fruits and seeds of plants are not always distributed by wind. Seeds often “travel” along streams and rivers, and are carried by sea currents and rain streams. For example, a coconut can remain afloat in the open sea for years without losing its viability. Often, an entire piece of land with palm trees and shrubs growing on it, as well as with the animals living there, can break off from the shore. Such islands begin to float with the current, spreading the seeds of their trees over thousands of kilometers.

Everything about everything. Volume 5 Likum Arkady

How are grass seeds spread?

Herbs are the most common plants in the world. There are about 7000 species of them. A sea of ​​grass covers fields sometimes covering thousands of square kilometers. They are called prairies, steppes, plains, valleys. This is the pampas South America, Russian steppes, South African velds. Many herbs reproduce using seeds. Seeds are spread in many ways. Some grass seeds are covered with long hairs and are carried by the wind. Some are rolling on the ground. Birds carry seeds in their beaks because they feed on them. When they fly with seeds, the seeds may fall from their beaks.

Some grass seeds have sharp spines. With these spines they cling to animals or people passing by the plant, and they are “transported” on skin or clothing. By chance, during trading expeditions, many grass seeds were transported over vast distances around the world. For example, ships carried lemon balm grass seeds from Africa to the New World.

Plant stems were used as bedding for slaves. When they were thrown on the floor, the seeds spilled out. This is how the grass spread from Africa to North America. Some grasses live for one season and then die. They need to be sown every year. Other herbs are perennial. Grasses in pastures or on your front lawn grow for years, and their roots survive winter well. In spring, young shoots grow from them.