Explain the experiment:
According to the experiment, Darwin proposed that after the tip of coleoptile is stimulated by unilateral light, it will transfer some kind of "influence" to the lower elongation area, so that the backlight surface of the elongation area grows faster than that of glossy surface, so the coleoptile will bend to light.
19 10 years, the experiment of Paulson Zhan Sen proved that the influence from the top of coleoptile can be transmitted to the bottom through agar plate.
Bayer's experiment in 19 14 proved that "influence" is a chemical substance. The stimulation produced at the top may be a chemical substance, and the uneven distribution of this chemical substance causes the curved growth of the coleoptile.
1928 the experiment of Dutch scientist winter proved that "influence" is indeed a chemical substance.
193 1 year, scientists successfully extracted IAA for the first time.
Other tropism types of extended data factories:
1, geotropism
The central part of the plant near the root tip is called a column, and the cells are rich in starch bodies, which are organelles for storing starch particles. Because of gravity, amyloplasts are always located at the lowest part of cells.
Auxin stimulates the elongation of stem tissue, but inhibits the growth of root tissue. Therefore, the growth of the lower part of the transverse root is inhibited, resulting in the downward bending of the root tip.
2. Tactile characteristics
Touch is an isotropic growth movement caused by contact stimulation. Thixotropy is also easier to observe. When plant tendrils come into contact with objects such as poles and sticks, they bend and wrap around these objects.
Contact stimulation is not due to uneven distribution of auxin, but the sensitivity of one side of stimulation to auxin is different from that of the other side. This is different from other orientation mechanisms. In some species, touch occurs very quickly, but in less than a minute. This shows that the change of cell expansion pressure is the main mechanism, and the outer cells elongate due to the increase of expansion pressure, which leads to the spiral rotation of tendrils.
3. Chemotaxis
Chemotaxis is one of the tropism movements of plants, and it is a growth reaction caused by uneven distribution of chemical substances. The growth of plant roots is chemotaxis. Roots always grow in fertile soil. One of the purposes of deep application is to make the roots of crops grow deeper into the soil to absorb more fertilizer.
4. hydrotropism
Hydrotropism, also called tropism, is a characteristic that roots tend to grow in wet places when soil moisture distribution is uneven. The roots of most higher plants are positive water.
Because the root system absorbs water, the water near the root system decreases, and the movement of water in the soil is slow, so the root system mainly obtains water from the soil through the continuous growth of the root system. The hydrophilicity of roots helps them occupy moist areas in the soil.
Baidu encyclopedia-phototropism