Chapter 36, Problem 17STP

Summary Introduction

To conclude:

The reason for ripening of bananas faster in a paper bag than on top of a plate and to suggest a method of improving the experiment.

Introduction:

Hormones are organic compounds that are made in one part of an organism and then transported to another part where they have an effect. Only a small amount of hormone can bring about a change on the organism. There are different types of hormones produced by plants which may cause cell division, growth and ripening of fruits. Different hormones include auxins, gibberellins, ethylene and cytokinins.

Answer to Problem 17STP

Bananas ripened faster in a paper bag than on top of a plate because the hormone ethylene reached the unripe bananas in a more concentrated form and triggered the process of ripening. When left in the open plate, ethylene being a gas diffused into the surroundings and did not reach the unripe fruits in concentrated form.

Ripening can also be fastened by placing a ripe fruit inside the paper bag or near the unripe fruit.

Explanation of Solution

Ethylene is a gaseous hormone found in plant tissues such as ripening fruits, dying leaves, and flowers. As it is a gaseous hormone it can easily diffuse through the spaces between cells. It causes cell walls of unripe fruits to weaken and complex carbohydrates to break down into simple sugars. The fruits after ethylene exposure become soft and sweet.

When the student in his experiment placed unripe bananas in a paper bag, the ethylene hormone released by bananas as they ripen reached all the bananas quickly and they got ripened faster. But when the bananas were placed on a plate and left uncovered, the hormone diffused into the surroundings and did not reach the unripe bananas in large amount. So they took time to ripen.

This experiment can be improved by placing a ripe fruit inside the paper bag. The ripe fruit will release ethylene which will hasten the process of ripening of unripe bananas.