Question

A ripe mango, kept with unripe mangoes causes their ripening. This is due to the release of the gaseous plant hormone
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Ethylene

Answer 1

Hint: This hormone can be produced from almost any part of the plant. It helps in oxygen transportation and controls stem elongation and flowering. The synthesis of this hormone can be inhibited by carbon dioxide, thus blocking the process of ripening. Through the air, this hormone can also act on other plants.

Complete answer
The plant hormones, which are also called phytohormones, are essential to plants as they perform several important functions like growth, flowering, fruit ripening, phototropism, stem elongation, and so on. There are several types of hormones found in a plant like Auxin, Cytokinin, Gibberellin, Ethylene, and so on. All these hormones control various functions in plants but ethylene is the only gaseous plant hormone that causes the ripening of fruit. It is commonly seen that unripe fruits like bananas, kept with ripe bananas, ripen overnight. It is because of ethylene released from the ripe banana, which promotes the ripening of the fruit. It does so by catalyzing the conversion of starch and acids in the unripe fruits into sugars, thereby ripening them.
So the correct answer is ‘(d) Ethylene’.

Additional Information: Ethylene plays an important role in hypocotyl elongation, root initiation, stem branching, change in color of the fruit during the ripening process, and promotion of the growth of roots to increase the absorbing capacity of water and minerals. It also interferes with the transport of other hormones like Auxin. It also induces the opening of flowers. Ethylene has several defined functions at different stages of plant development like cell division, cell elongation, cell death, response to environmental condition and competition, plant growth, response to gravity, flowering, and fruit ripening.

Note: Ethylene is used to develop female flowers in a male plant. Ethylene is also used as an artificial fruit ripener. Simultaneously, the synthesis of ethylene can be inhibited by carbon dioxide, and hence the ripening can also be controlled. This is sometimes implemented by farmers in large scale manufacturing and export of fruits between two distant countries.