explain any three roles of ethylene
Answers
Ethylene is a gaseous hydrocarbon with the structure of H2C=CH2. It is reasonably not necessary for normal vegetative growth of the plant but has a notable effect on the growth of roots and shoots. Ethylene occurs in plants when high intensities of auxins are provided to the plant tissue. It occurs in all plant organs- roots, leaves, stem, bulbs, seeds, fruits, tubers, and so on.
The rate of production of ethylene may vary depending on the structure of the plant as different tissue secrete different amounts of ethylene. It is also determined by the stage of development the plant is going through. Studies have shown that ethylene is generally located in the peripheral tissues of the plants. It also depends on the type we look at, for example in peach and avocado seeds it is noticed that more ethylene concentration is found on the seed coat, but in tomato fruit and mung bean hypocotyls, it takes its origin from the epidermal region.
Ethylene Structure
As it could be seen that ethylene is a basic hydrocarbon derived from ethane molecule. Here both the carbon atom shares a double bond, and the remaining valencies are filled by hydrogen atoms. It is to be noted that the carbon-carbon double bond has a length of about 133.9pm and the carbon-hydrogen bond has a length of 108.7pm and the angle between the carbon and hydrogen from the inner aspect is 121.3⁰
Ethylene Formula
The formula for ethylene is H2C=CH2. Ethylene has high importance in plant physiology and despite that is was difficult to find out how ethylene was produced in the plants and what pathway it followed to be secreted. After the evolution and invention of Gas chromatography, volatile ethylene substance could be isolated and its physiological importance could be studied.
Few scientists in the early 1960s showed that ethylene was actually derived from an amino acid called Methionine in apple tissues. Later in the 1970s Yang and Adam have illustrated that the conversion of Methionine to Ethylene takes place by the production of an intermediate compound called S-adenosylmethionine (SAM) by the apple tissue. They further demonstrated that the accumulation of a compound called 1-aminocyclopropane-1-carboxylic acid (ACC) in apple tissue fed with Methionine had inhibited the production of ethylene in anaerobic conditions but on the introduction of oxygen the labeled ACC was rapidly converted to ethylene.
Ethylene as a Plant Hormone
Ethylene acts as a significant hormone that regulates and mediates complex cycles in plants, regarding their growth and development, and their survival throughout their life cycle.
The main function and interest of the scientist for ethylene is its ability to ripen fruits and achieve senescence. This ability has been the major focus for food biotechnologists as it can be used to fasten the ripening of fruits where ethylene is the main hormone, for example, tomato and banana fruits. Food biotechnologists aim to achieve the ability to control the fruit ripening process by controlling the synthesis of ethylene hormone.
To understand the function of ethylene, we first understand how a plant secretes ethylene in the tissues. Ethylene synthesis is a biochemical pathway consisting of two-steps. It starts with a compound called SAM (S-adenosyl-L-methionine). SAM is changed to ACC with the help of the enzyme ACS (ACC synthase). ACC is turned to ethylene via an enzyme called ACO (ACC oxidase).
It is to be understood that both the enzymes ACS along with ACO are emitted by multiple gene coding family that synchronizes with one another in situations like drought, flood, wound, applying external pressure, and attack from a pathogen.