Tillering of winter wheat and its yield
Tillering is important for the formation of a high yield of winter wheat. In the phase of 3-4 leaves, a thickening is formed on the underground part of the wheat stalk, which is called a tillering node. The potential of tillering of plants is programmed, first of all, by the force of the development of the tillering node. This organ of the plant consists of several underground nodes that are close to each other. Under normal growing conditions, it is located at a depth of 1-3 cm. All parts of the future plant are located in the tillering node from the very beginning. This is the most important organ of winter wheat.
The centers of regeneration and neoplasm of organs are the meristem of tillering nodes with a reserve of energy and active substances. When depleted, they cannot generate new tissues and organs. The death of the node due to unfavorable conditions or damage by pests leads to the destruction of the whole plant. In the event of the death of part or even all of the leaves, or damage to part of the root system with a live tillering node, the plant retains the possibility of further growth and development. It has an intact growth cone and lateral buds, which are located in the tillering node below the soil surface for a long time during the autumn and spring tillering phase (before entering the tube). This is an evolutionary natural adaptation of cereals to tolerate unfavorable conditions.
The number of stems per plant can vary significantly. According to the standard technology, it is 1-3 stems, and only on liquefied crops it can reach 10 or more. However, the potential for the formation of side shoots in winter wheat is extremely high. Productive bushiness when creating appropriate living conditions can reach up to 100 ears and above. Wheat bushes with a feeding area of 30x70 cm give up to 100 stems with a capacity of 100-120 g. And in artificial conditions, you can get plants with more than 300 stems. For example, in a special experiment, 334 shoots grew in the Odessa 3 variety.
There are two opposite views on the ability of winter wheat to bush and the significance of this phenomenon for the harvest. Some researchers consider tillering an important reserve for yield growth. Others argue that an increase in the number of shoots affects a decrease in yield, i.e. they deny the expediency of tillering. In their opinion, winter wheat is characterized by asynchrony in the development of shoots, which leads to their reduction in the late growth phases. Tillering shoots that have been preserved for harvesting are less productive compared to the main one. In addition, secondary stems that do not produce grain, unproductively use moisture, light and nutrients.
The secondary role of tillering in the formation of the crop allowed scientists to come to the conclusion that it is advisable to breed varieties with a low tillering coefficient, a rapidly growing first (main) stem and an early reduction of lateral shoots, that is, mainly single-stemmed ones. To achieve uniformity of the productive stem, in which there will be no competition between highly developed multi-stem and underdeveloped single-stem plants, it is necessary to apply certain elements of technology, in particular, to increase the seeding rate.
But if we approach this problem from the other side, we will find that with large seeding rates, it is possible to influence only such an indicator of the crop structure as the density of the productive stem. The yield potential of winter wheat is determined only by the density of crops. It is almost impossible to increase the tillering coefficient in such thickened agrophytocenoses. It is problematic to increase the productivity elements of the ear, especially the number of grains in the ear, and its mass, as a result of which the possibilities of controlling the structure of the crop are severely limited. Therefore, most scientists refute the concept of a single-stemmed plant.
Thus, a bush consisting of the main and two or three lateral stems with a well-developed secondary root system should be formed from the seed. With this development, the bush gives several productive stems that develop almost simultaneously. This is the most healthy and powerful type of bush that is resistant to lodging, diseases. It is important to prevent the formation of stems of the second and subsequent orders.
The first shoots – the main one and three of the buds of the first three real leaves-form ears that are not inferior to the main one in productivity. With a sufficient feeding area, the first 4-5 tillering shoots almost do not differ either in the size of the straw, or in the size of the ear, or the number of spikelets and grains in them.
There are many experimental data that prove the value of not only lateral productive shoots. According to the researchers, side shoots, which do not even form grains and are temporary competitors in the struggle for nutrients, light and moisture, have a positive effect on crop yield. They form an additional root system, which, after their death, works for the plant. The root system of the plant transmits water and nutrients to all shoots through the tillering node. Absorbing force, the power of the root system in the process of dumping part of the shoots is enhanced. There are fewer shoots left for the same root system, which means that their best growth and development are ensured. With the help of shoots, the assimilating apparatus increases, more plastic substances accumulate, which later move to the ear-bearing stems and increase their productivity.
Multi-stem plants have a better developed aboveground mass and root system, are more resistant to unfavorable growth conditions and are able to form higher productivity compared to underdeveloped single-stem plants. The discharge of individual shoots during the exit into the tube in highly bushy plants is not equivalent to the death of a whole poorly-grown plant with a large stem density. The loss of plants creates sparseness and unevenness of their placement and stems. Reduction of a part of the stems, on the contrary, contributes to the formation of a uniformly placed stem, since their main part falls out in thickened places. Therefore, bushiness has a positive effect on the yield of winter wheat.
The intensity of tillering depends on many factors. First of all, these are those natural factors that are almost not amenable to human regulation, but have a primary influence on tillering. This includes soil fertility, moisture availability, temperature regime, lighting intensity, daylight length, etc.
The tillering energy is strongly influenced by the duration of tillering, i.e. the time from the germination phase to the exit into the tube. The continuation of the tillering phase contributes to the formation of more lateral shoots.
Winter wheat can have two tillering periods – autumn and spring, depending on the timing of sowing and other factors. In autumn, tillering continues until the average daily temperatures drop to 2-3°C. The duration of autumn tillering under normal conditions is 25-30 days, spring tillering is 30-35 days.
In spring, tillering resumes with the beginning of the spring growing season and continues until the beginning of the release into the tube, when the average daily temperature rises to 10-12°C. With late sowing dates and the absence of autumn tillering, the density of the stem is formed due to spring tillering. It can be significantly enhanced by the use of morphoregulators (retardants) and the first nitrogen recharge.
There is a widespread opinion that spring tillering almost does not produce productive stems, but this applies only to those crops where a high density of the stem was formed in autumn, or in conditions of low moisture reserves.
In well-bushy plants from autumn, the root system will work in the spring for autumn shoots, which take away the main part of nutrients and, thus, limit spring tillering altogether or weaken the development of spring shoots. In the absence of autumn shoots, all the power of growth and development of the plant is directed to the formation of strong, well-developed spring shoots that can ensure the productivity of the colossus at the level of the productivity of shoots formed in autumn. Of course, in order to fully realize the productivity of spring shoots, a technology adapted to specific meteorological conditions with constant monitoring throughout the spring-summer growing season is necessary. The main thing is to ensure the development of a high-yielding plant.to the section