The growth and development of higher plants depend on roots to absorb water and inorganic substances from the soil, carbon dioxide and light, and some organic substances such as protein, sugar and fat. In addition, it also requires the organic substances with high physiological activity produced by the plant itself. Although the content of the organic substances is very small in the plant body, they play a very important role and can directly affect the growth, development and metabolism of the plant. If the plant lacks it, it can not grow normally, or even survive. Such organic substances with high physiological activity are called plant hormones. Plant hormones are the normal metabolic products of plants. Different plant hormones are produced by different tissues and organs, and then transported to other organs, which play an important role in regulating plant growth. Some important links in the process of plant growth, such as germination, rooting, seedling emergence, growth, organ differentiation, flowering and bearing, maturity and aging, organ shedding, seed dormancy, are all regulated and controlled by plant hormones.

After decades of research, there are five major categories of plant hormones that have been found and recognized, which can be divided into two aspects according to their physiological functions: promoting growth and inhibiting growth. It is of great significance for people to understand and study plant hormones to master and control plant growth, improve quality, overcome adversity and even increase yield.

The distribution of five major hormones in plants is uneven. Auxin, gibberellin and cytokinin mainly exist in the young parts of plant tissues, such as the tip of stem and root, young fruit and young seed; Abscisic acid and ethylene mainly exist in the aged tissues, exfoliated organs and mature fruits of plants. The content of plant hormones in the plant body is not invariable, such as the change of wheat from heading to filling, the amount of cytokinin in the wheat ear after heading is large, the content reaches the peak at the end of flowering, followed by gibberellin, and reaches the high level three weeks after flowering, the content of auxin begins to increase four weeks after heading, and decreases at maturity.

Because the content of plant hormones in plants is very small, it is impossible to extract them from plants and apply them in production. Now people can synthesize substances with physiological activity by simulating the chemical structure of natural hormones in plants with chemical methods, or synthesize substances with physiological activity that are completely different from the chemical structure of natural hormones. These substances have similar effects of plant hormones and can also play a role in regulating plant growth and development. These substances are collectively called plant growth regulators or chemical regulators.

Plant growth regulators can generally be divided into two categories. One is to promote plant growth and development, such as naphthoic acid for promoting rooting, gibberellin for breaking dormancy, and 6-benzyladenine for preventing aging. These are called stimulants; The other type is called inhibitor, which can inhibit the growth and development of plants, such as CCC, which can prevent cotton and wheat from growing crazily, and cyanogen, which can prevent garlic, onion and potato from sprouting.

However, this method is not absolute, because the same growth regulator can be used as a stimulant at low concentrations and as an inhibitor at high concentrations. For example, naphthoic acid can stimulate the growth of rice seedlings at dozens of PPM concentrations, but 1000ppm concentration can inhibit the growth of rice seedlings; For example, 2,4-D, 10-20ppm concentration can promote growth and prevent abscission, 100ppm will inhibit plant growth, and 1000ppm will kill dicotyledons. In addition, different plants and even different organs of the same plant have different responses to growth regulators. For example, auxin is generally sensitive to roots, followed by buds, and stems are less sensitive. At the same concentration, it can promote the stems, but may inhibit the roots.

So why is ethephon a plant growth regulator? This starts with the role of ethylene. A long time ago, people found that a kind of gas emitted from rotten fruits can accelerate the ripening of surrounding fruits. In the early 1930s, it was confirmed that the effective component of the gas released from fruit was ethylene, which was a natural substance. Later, it was further discovered that the roots, stems, leaves, flowers, fruits and other organs of plants can produce ethylene. Ethylene is produced by fruit and promotes fruit ripening. The relationship between fruit ripening and ethylene naturally attracted people's attention. By the 1960s, the use of gas chromatography, which can detect very small amounts of ethylene, deepened people's understanding of ethylene. It is not only related to fruit ripening, but also related to plant cell division and expansion, seed dormancy and germination, flowering, sex differentiation, aging Important physiological processes such as abscission are closely related. Ethylene is a normal metabolite of plants, widely exists in plants, and plays a very important role in regulating plant growth, development and metabolism. Therefore, ethylene is recognized as an endogenous hormone of plants.

Although ethylene has a wide range of regulatory effects on plants, its application is limited due to its inconvenient storage, transportation and use as a gas. Later, it was found that ethylene could be produced from ethephon. Ethephon can release ethylene under certain conditions (such as alkali). Ethephon can be mixed into a certain concentration of water solution to spray or soak the plant, so that Ethephon can be decomposed in the plant to produce ethylene, and then play a role in regulating the growth and development of the plant, which can be considered as Ethephon is a plant growth regulator. In fact, the use of ethephon on plants is a convenient method of applying ethylene to plants.

Since 1968, ethephon has been used as an ethylene release agent in the research of plant growth regulators. In 1971, the Shanghai Institute of Plant Physiology of the Chinese Academy of Sciences and Shanghai Pengpu Chemical Plant, the Beijing Institute of Botany of the Chinese Academy of Sciences and the Second Beijing Pesticide Plant, and other units simultaneously carried out the synthesis and research of ethephon. In the same year, it was tested on rubber, and the obvious effect of increasing production of rubber latex was first obtained. Since then, many units in the country have carried out a lot of experimental research and demonstration and promotion work, so that the research and application of ethephon have made great progress in both depth and breadth.

There are varieties of crops that use ethephon in agriculture in China, including cash crops such as rubber, Qinshu, pine, cotton, tobacco, tea, kenaf, jute, rape, beet, grass, tulu incense, Indian rosewood, sugarcane, moso bamboo, wutong, etc; Gardening crops such as tomato, banana, pineapple, orange, watermelon, persimmon, peach, apple, apricot, pear, litchi, grape, hawthorn, jujube, chestnut, cucumber, gourd, melon, pumpkin, pepper, spinach, etc; There are more than 40 kinds of food crops, such as rice, wheat, corn and sorghum. The trial crops are more extensive than other growth regulators. It has been proved through repeated practice in various places that ethephon can increase the rubber discharge and yield of rubber and raw materials; Ripening of bananas, tomatoes and other fruits and cotton; Dwarfing of rice and maize; Cucumber and gourd induce more female flowers; Wheat emasculation; Tea flower removal; Jujube and hawthorn have significant effects in accelerating the fall. At present, cotton, rubber, rice and other crops with large area of ethephon are used in agricultural production in China. The application of ethephon in cotton was listed as a national key extension project by the Ministry of Agriculture in 1980, and has received good economic benefits through large-scale use. For this reason, he won the second prize of the Technology Improvement Award of the Ministry of Agriculture in 1980 and the Technology Promotion and Application Award issued by the National Science and Technology Commission and the Agriculture Commission in 1982.

Although the research on the application of ethephon in agriculture has only a history of more than ten years, it has developed rapidly. It can be believed that ethephon will play a greater role in promoting China's agricultural production in the future.