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rom smog to science: How was the miraculous effect of ethylene discovered in the 19th century
Ethylene, with the chemical formula CH2=CH2, is an unsaturated hydrocarbon gas that exists in nature as a natural plant hormone. This is the simplest olefin gas and the first gas known to act as a hormone. Ethylene acts in trace amounts at all stages of plant life, by stimulating or regulating the ripening of fruits, the opening of flowers, the shedding of leaves, and even in aquatic and semi-aquatic plants, promoting rapid elongation to escape submergence, the escape response. It is especially important for rice farming.
"Ethylene is a powerful growth regulator that affects many plant physiological processes."
Commercial fruit ripening rooms typically use a "catalytic generator" to convert liquid ethanol into ethylene gas. Typically during the ripening process, ethylene concentrations remain between 500 and 2000 ppm per cubic meter for 24 to 48 hours. When gassing in ripening rooms, CO2 levels must be carefully controlled, as high temperatures for ripening (20°C; 68°F) can result in CO2 concentrations of 10% within 24 hours.
History
Ethylene has a long history of use in agriculture. Ancient Egyptians would injure figs to promote ripening (the wound stimulates the production of ethylene in the plant tissue). In ancient China, incense was burned in a sealed room to promote the ripening of pears. In the 19th century, city dwellers noticed that gas leaks from street lamps were causing plant growth to stunt, flowers to wither, and leaves to fall prematurely. In 1874, scientists discovered that smoke could make pineapple fields bloom. The smoke contained ethylene, and later the smoke was replaced by ethylene generators such as "vinyl alcohol" or "naphthaleneacetic acid".
"Observations in the 19th century revealed the important effects of ethylene in smoke on plant growth."
Scientific research on ethylene as a factor in plant physiology began in the late 19th century. In 1896, Russian botanist Dimitri Nelyubov studied peas and discovered that the active ingredient in illuminating gas is ethylene, which can stimulate the movement of peas. He reported this discovery in 1901. In 1917, Sarah Dought also demonstrated that ethylene from illuminant gas could stimulate abscission in plants. Florida farmers, who routinely ripen crops in greenhouses by lighting oil lamps, initially thought this was due to heat. In 1924, Frank E. Denny discovered that it was ethylene released by petroleum lamps that promoted ripening, and wrote in the Botanical Journal:
"Ethylene is so effective at inducing the desired effect that even concentrations of just one part per million in air can cause a green lemon to turn yellow in about six to ten days."
In the same year, Denny published a detailed experimental report and experimentally proved the advantages of using ethylene over the use of petroleum. In 1934, British biologist Richard Gang discovered that chemicals in ripe bananas could cause green bananas to ripen, and he demonstrated that ethylene could also trigger this growth effect.
Ethylene synthesis pathway
Ethylene is synthesized by nearly all parts of higher plants, including leaves, stems, roots, flowers, fruits, tubers, and seeds. Ethylene production is regulated by various developmental and environmental factors. During the life of a plant, certain growth stages trigger the production of ethylene, such as germination, fruit ripening, leaf shedding and flower senescence. The ethylene synthesis pathway is called the Yang cycle, which is based on the key contributions made by scientist Chang Fa Yang. The synthesis of ethylene involves the conversion of the amino acid methionine to S-adenosyl-L-methionine, followed by the production of 1-aminocyclopropane-1-carboxylic acid via ACC synthase, which ultimately produces ethylene in the presence of oxygen.
"The synthesis of ethylene is induced by endogenous or exogenous ethylene."
Ethylene perception in plants is regulated by a group of transmembrane protein dimers, such as the ETR1 protein in Arabidopsis thaliana. The cloning of these sensory factors has been successfully achieved in many plants. A series of plant responses triggered by ethylene have also been identified, including calyx aging, fruit ripening, and root hair growth. The discovery of these reaction patterns leads us to further understand the impact of environmental and biological factors on plant physiology.
Remember the Effects of Ethylene
In agriculture, ethylene not only has a positive impact on plant maturation and flowering, but also helps overcome challenges such as environmental stress and salt damage. However, when ethylene is present in excess, it can seriously affect the storage life of fruits, promote the aging of flowers, accelerate their withering, and lead to economic losses.
"How to effectively utilize ethylene for plant growth and maturation without causing adverse consequences remains an important challenge facing scientists."
Although the research on ethylene continues to deepen, its mechanism still needs to be more comprehensively explored. Future research may reveal more mysteries of natural hormones, allowing us to rethink what kind of future the scientific development of plant growth will bring?
