(A) The concept of root hair The root hair is a mature absorbent tissue specialized by some epidermal cells of the root. The root covering is the typical characteristic of the mature root section. The mature parts of the tip of wheat primary roots or secondary roots (or even their branches) (except for the tip part 0.1 to 1.5 M apart from the apical meristem) can produce root hair, but the root hair on the surface area of ​​the primary root unit The number of roots is less than the number of roots; there are many root hairs on a wheat root, with hundreds of square millimeters per square millimeter, and the total length of all root hairs connected can reach 10km or more. Therefore, the occurrence of root hairs significantly increases the total surface area of ​​the root system and greatly enhances the absorption function.
(b) Root hair differentiation and formation As soon as the epidermal cells elongate, the root hairs begin to differentiate. The formation process can be roughly summarized as follows: Most RNA-rich hair cells in the mature area, that is, a corner or middle of a short cell protrudes outward to form a hemispherical process. Afterwards, the protrusion gradually extends in a tubular shape to form a long tube-shaped root hair having no apical seal structure. The relevant research results show that the length of the root hair is generally 0.5-10mm and the diameter is about 5-17um. The root hair grows rapidly but has a short life span. The functional period of a single root hair (cell) is only 10-20 d or less. In general, root hairs on older root segments have lost their absorption function and gradually shrink, die, and fall off. But when conditions are right. The root hair on old roots can also survive longer, but they have lost their absorption function. As the meristem-derived cells continue to increase and differentiate, and the elongation zone continues to extend backward, the new root hairs are regenerated in the upper part of the secondary long-window and replace the dead root hairs. As a result of the replacement of the old and new root hairs and the occurrence of root hairs, the root hairs area goes deeper into the soil as the roots grow and develop. Because the outer wall of the root hair cell contains cellulose, pectin and stratum corneum, the viscosity is relatively large. Therefore, when continuously extending forward and penetrating the soil, a large amount of soil particles often adhere to the root hair. The phenomenon of root hair adhering to soil particles is beneficial to its functions such as absorption and fixation.
(3) Influencing Factors of Root Hair Occurrence and Function Root hair development is greatly affected by environmental conditions. The Tian-Qian test results show that the root hair is very sensitive to changes in soil moisture. Under moist soil conditions, more root hairs occur; under soil drought or waterlogging conditions, less root hairs occur. It is worth noting that soil drought or insufficient water supply in the plant often leads to loss of root hair function, followed by wilting and withering. In this case, even if the water is rehydrated quickly, new root hairs will only occur within a few days. Ma Yuanxi et al. observed the root system in the underground moisture chamber. The number of days from the occurrence of the root hair to the appearance of bending (normal life period) varies according to conditions such as the ambient temperature, and averages of 15.2, 20.9, 25.0, 18.5, 0.5 in the months of November, December and the following year of 1, 2, 3, and April, respectively. The above observations over 10.3 days have a significant correlation with the monthly average temperature change in Zhengzhou, Henan Province, that is, when the temperature is lower, the root hair life time is longer, and vice versa. It was also observed that most of the root hairs in the glass wall were white and transparent before heading, and their morphology was normal. Even the root hairs of the first and second branching roots were the same; but after flowering, most of the root hairs quickly shrank and turned yellow. In addition to soil moisture and temperature. Factors such as soil type and texture, soil fertility, and cultivation and cultivation practices also have a major impact on the production of club hair and its functioning.
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