Question

When mature green tomatoes are put in a sealed plastic bag, they remain green for several days. But if one or two ripe apples are kept along with green tomatoes in the sealed container, the tomatoes turn red within a few days. It may be due to the fact that ripe apples:
A. produce ethylene which induces tomato ripening
B. remove carbon dioxide which initiates fruit ripening
C. absorb ethylene which induces tomato ripening
D. absorb carbon dioxide released from green tomatoes

Answer 1

Hint: Fruits often produce certain hormones during different stages of their life. One of the plant growth regulating hormones is responsible for inducing ripening of the fruits. It is a gaseous hormone that diffuses around and causes ripening of unripe fruits present in its vicinity.

Complete answer:
Ethylene is a gas hormone that helps in the ripening of fruits in plants thus also known as fruit ripening hormone. Different fruits respond to this at varying intensity. Depending upon this, fruits can be classified into 2 main categories: Climacteric fruits and Non-climacteric fruits. Climacteric fruits are those in which ripening is accompanied by a burst of ethylene. These can also respond to external ethylene thereby causing their speedy ripening. For eg: apples, tomatoes, pears, and avocados. Whereas Non-climacteric fruits are those in which the ethylene production does not increase during their ripening.

Apples are one of the most common climacteric fruits which produce a large amount of ethylene during their ripening. An initial Exposure to even a small amount of ethylene can trigger larger production of ethylene in them which in turn increases the metabolism and accelerates the process of changes which ultimately leads to the ripening of these fruits.

Thus, if few ripened apples are kept with mature tomatoes (which are also climacteric vegetables) in a plastic bag they can speed up the process of ripening by providing the initial trigger of ethylene which in turn will cause an ethylene burst in tomatoes causing them to ripen faster.

Hence, the correct answer is option (A). Ripe apples can induce green tomatoes to ripe when both (ripe apples and green tomatoes) are placed in close vicinity.

Note: The ripening process can be slowed by either reducing the production of ethylene by the fruit or by blocking its activity. Ethylene action gets inhibited in presence of carbon dioxide. Other chemicals like potassium permanganate can also slow down the ripening process.