What makes plants grow? Do you know how some plants grow? We will show you How to grow plants? From pollination to pollination: Life cycle

There are plants that will forever remain short, like grass, and there are those that become real giants in a few years. People turn their huge trunks into wood, which they use for various purposes. Large trees are felled with a chainsaw. Poor trees! People easily cut them down, but for a tree to grow big and tall, many years must pass.

climbing stems

If the plant stem is flexible and thin, it does not have enough strength to stay straight. In this case, a support is created for it - a stick is stuck into the ground next to it, around which the plant will curl. This is how a bean sprout behaves as it reaches for the light.

Plants are used for more than just food. Tree trunks are used to make wood, pulp for making paper, and textile fiber. The green world allows man to obtain many natural flavors and chemicals for industry.

Tree age

"Climbing" stems

Some plants with weak stems, such as ivy, have learned to cling to surrounding objects. They stick to various surfaces with their little “fingers,” which have very sticky little suction cups on the tips.

Enemies

Since plant roots are a storehouse of nutrients, many insects, birds and animals want to feast on them. These are enemies of plants. The most important underground pests are moles, which, by digging their underground passages, damage the roots of plants.

Botany Beginning

How do plants grow? Surprisingly, in general, the life of plants is very similar to how people grow. Everything, right down to many types of plants.

• From pollination to pollination - the life cycle of a plant

How plants grow. How this can be changed

Just as humans have essential needs for survival, all plants require several basic elements to grow and thrive, including...

• Minerals from the soil (the more nutrient rich the soil, the better the plant will grow)
• Air (carbon dioxide, hydrogen and oxygen)
• sunlight
• Correct soil temperature
• Correct air temperature

How much a plant needs of each element initially depends on the plant's original habitat. For example, rainforest plants that require constantly wet and warm conditions might obviously not survive in the desert.

But according to human desire, the ability of a plant should not completely depend on nature. Organic farmers, gardeners, scientists and researchers have “modified” the characteristics of many essential plants to enable them to thrive in other environments.

Continuing with the example of rainforest plants, if a farmer notices that one crop plant does not need as much water to grow and bear fruit, he may begin to cross-pollinate that plant with another plant with the required qualities, in an attempt to start a new "line" (called "species") to create more resilient tropical forest plants. With time and constant cross-pollination, more and more plants become tolerant, so rainforest plants can “learn” to survive in conditions that are significantly different from their native lands.

This intentional cross-pollination can be applied to any characteristic of the plant... from resistance (roughly speaking to the plant's immunity), flower color, fruit flavor, and root depth.

Now let's move on to what happens within and between plants. What allows them to grow, prosper and multiply...

How to grow plants? From pollination to pollination: Life cycle

At the risk of oversimplifying, the seven stages of the plant growing cycle are the main...

1. Pollination
2. Fertilization
3. Seed formation
4. Seed dispersal
5. Germination
6. Continued growth
7. Pollination

1. Pollination

While some plants can reproduce asexually (for example, plant a root cutting or stem cutting and a new plant will emerge), most plants reproduce sexually through pollination.

During pollination, pollen grains carrying male sperm (gametes) are carried by insects or animals to the female part of the plant, where the gametes come into contact with the female egg. This can occur either between two plants (cross-pollination) or within the same plant (self-pollination). The reproductive organs of sexually reproducing plants are located in what we usually call .

2. Fertilization

In some plant species, when a pollen grain containing gametes comes into contact with the female part of the flower (the pistil), the pollen grain travels down a tube in an attempt to reach the plant's egg cell.

In some plants, pollen can travel through a tube up to 40 cm! When this happens, the gamete will pass through the pollen tube, reach the egg and fertilize the egg.

In other types of plants, the female parts contain watery fluids through which flagellated sperm swim their way to fertilize the eggs.

3. Seed Formation

Seed formation begins inside the mother plant or part of the plant. It then continues to grow inside the fruit in some types of plants (angiosperms) or open on the perianth in other types (gymnosperms).

4. Seed dispersal

Once the fruit of a plant is ripe or the fruit has opened, its seeds are dispersed by wind, water, animals or insects at a time when conditions are ideal for the plant seeds to germinate and grow.

5. Germination

Germination occurs when a plant sprouts from a seed and begins to grow, producing its familiar parts, including roots, stems, and leaves. Germination occurs after a plant's seed has landed on the ground or has been trampled into the ground or buried in the surrounding environment (i.e. soil) .

6. Continued growth

Unlike animal stem cells, which can only create new cell types during the early stages of an animal's development, plants always create new parts based on need from a special tissue called a meristem. There are two types of meristems - one for the roots and one for the top - and consists of different types of cells that will "fire" at the right moment (we should say, have an effect on the root or the stem).

The process of continuous plant growth is made possible by several processes, including photosynthesis, nutrient transfer and transpiration (see our Page for more information on these).

7. Pollination

Once the plant has grown and matured, it produces its own flowers for pollination and fertilization. May the circle of life continue forever!

The problem of “invasive”, that is, plant species introduced to a given area, has recently occupied not only environmental scientists, but also the general public. The fact is that, once in a new territory, invasive species often begin to reproduce extremely intensively, become dominant in local communities, and sometimes even turn into harmful weeds (see: Invasive species). The study of such plants has shown that in new habitats they are selected for a higher growth rate. And this becomes possible by reducing the cost of developing protection from herbivorous animals.

Another factor that may determine the success of invasive plant species is the acceleration of nitrogen cycling, an element that is often in short supply in the soil. It is assumed that the stems and leaves of rapidly growing invaders are characterized by a slightly lower cellulose content (their cell walls are thinner). They are softer and more delicate. The organic matter of such plants, after they die, is quickly decomposed by fungi and bacteria. Accordingly, the processes of nitrification—the conversion of ammonium nitrogen into nitrites and nitrates, that is, into a form suitable for new consumption by plants—go faster. For example, the sycamore maple brought to Canada from Europe Acer platanoides accelerates the processes of mineralization (decomposition of organic matter in the soil) and nitrification compared to the native species - sugar maple Acer saccharum.

If introduced species grow faster in a new place than in their homeland, it can only be assumed that selection is taking place in their populations to enhance the properties responsible for rapid growth. But the question immediately arises: at the expense of what resources is this possible and why is this not observed at home? A special study on this matter was undertaken by a group of specialists from China, the USA, Mexico and India. The object of their study was a plant (subshrub) from the Asteraceae family - Ageratina bells ( Ageratina adenophora). Ageratina comes from Mexico, but from there it spread widely throughout the subtropical regions of other continents, becoming a typical invasive species.

The bulk of the work was carried out in the Tropical Botanical Garden of the Chinese Academy of Sciences in Xishuangbanna Tropical Botanical Garden in the southeastern part of China (Yunnan Province, 21°56"N, 101°15"E). The ageratina plants used in the experiment were obtained from seeds collected in three growing areas: in its native Mexico and in two areas where the plant is introduced - India and China. The researchers tried to create representative samples from each growing location. In each case, seeds were collected from five different populations, and in each population, from 15 plants that did not grow in close proximity to each other. In a laboratory in China, seeds were germinated under standard conditions, and young plants that reached 10 cm in height were planted in plots in open ground. No fertilizers or additional watering were used. The characteristics of individual leaves from different plants were periodically measured, and 8 months after germination, under controlled laboratory conditions under the same light level and different levels of CO 2 in the air, the rate of photosynthesis was assessed, as well as the ratio of nitrogen going directly to photosynthesis and deposited in the cell walls.

The experimental results confirmed the authors' expectations. The proportion of nitrogen used for photosynthesis (that is, directly for plant weight gain) in plants from areas of invasion (from India and China) was different, but in both cases it was significantly higher than in plants from places of original growth (from Mexico). The photosynthetic rate of Ageratina from China and India was higher than that of Ageratina from Mexico. Not surprisingly, plants from areas where they are invasive turned out to be taller and with larger leaves, although the density of their leaf tissue was significantly lower. This result means that ageratina plants in new habitats invest more resources directly into growth, but this happens at the expense of reducing spending on the formation of protective structures.

Sources:
1) Marnie E. Rout, Ragan M. Callaway. An invasive plant paradox // Science. 2009. V. 324. P. 734-735.
2) Yu-Long Fenga, Yan-Bao Leia, Rui-Fang Wanga et al. Evolutionary tradeoffs for nitrogen allocation to photosynthesis versus cell walls in an invasive plant // PNAS. 2009. V. 106. P. 1853-1856 (the entire article is in the public domain).

See also:
1) A. M. Gilyarov. Why do invasive species thrive? // Nature. 2002. № 10.
2) John N. Klironomos. Feedback with soil biota contributes to plant rarity and invasiveness in communities // Nature. 2002. V. 417. P. 67-70.
3) European weed is destroying American forests, “Elements”, 04/27/2006.

Alexey Gilyarov

Plant growth occurs at the apical growth points

Plant development continues after the embryonic stage

Plant growth depends on the environment

The main and most obvious feature plants is that they do not walk, crawl or swim, but grow in space.

When we people growing, the number of cells in our body increases more or less evenly. All our organs and limbs grow in proportion, and we, as adults, are large copies of those forms that were characteristic of our childhood. Plants behave differently.

Instead of grow evenly in all directions in such a way that all parts contribute equally to the increase in size; they grow only at a few special points, which remain “young” throughout the life of the plant.

These points are called meristems. The figure below shows the location of meristems in a plant. "Primary" or "apical" meristems are found at root tips and shoot apices and are the sites of most active cell division as new cells are needed for the growth process. As a result of the formation of new cells, the meristem moves away from the old parts of the plant.

Thereby roots spread deeply into the soil, and the shoots into the atmosphere, towards sunlight. The material from the primary meristem gives the plant its height, and as a result of cell division in the "secondary" meristem (called the "cambium") located on the sides of mature roots and stems, they increase in girth.

In order to a plant has formed, the growth of primary meristems must have a certain direction. Disorderly growth will result in a mass of disorganized tissue. Therefore, growth occurs along the direction of the axis passing from the roots to the apex. This is the main growth axis along which all the lateral organs of the plant (for example leaves and flowers) are formed.

The sections of this axis located above the ground and in depth have different functions. The top grows upward, that is, it is directed against gravity, towards the light. In this case, the leaves can be turned towards the sun, and the flowers are exposed to light and can be visited by insects. On the opposite side, roots grow in the direction of gravity, in the direction opposite to the light. While in the soil, they firmly strengthen the above-ground parts of the plant and absorb water and minerals necessary for growth.

As apical meristem at the top of the plant it grows upward, and at the roots it grows downward, these two points of growth diverge further and further. This raises several purely mechanical problems. To transport nutrients produced in the leaves to the roots and to transport water and mineral salts in the opposite direction, special conductive channels are required.

Along with the, as the plant grows, the part of it located between the two growth points must be strengthened in order to provide structural support to the constantly advancing end sections. In the future, we will see how special thickening of cell walls strengthens the new sections of the plant stem that are formed and allows them to withstand the stresses associated with further growth.

Since the body plants differs from that of animals, their growth is much more dependent on the environment. Growth and/or its direction in plants depend significantly on gravity, temperature, daylight hours and direction of light. Thus, if the general structure of the animal’s body can be imagined already in the embryonic period, the structure of the plant is much more plastic; it continues to develop in response to changing external conditions, and its shape changes due to the formation of branches, as well as flowers and leaves.

This ability to adapt due to the specific location of organs depends on the plant's ability to continuously grow. Another consequence of plants' ability to support the growth of meristem points is that they can grow larger and live longer than any animal that has ever existed on Earth. For example, the weight of giant trees growing in North America can reach 2000 tons, and their height is more than 100 meters (~330 feet). The age of such trees can be several thousand years.