If a mutant plant were created that lacked the receptor for ethylene, its fruit would
The correct answer and explanation is:
Correct Answer: Fail to ripen properly
Explanation (300 words):
Ethylene is a plant hormone that plays a central role in regulating various aspects of growth, development, and stress responses. One of its most well-known functions is in fruit ripening, especially in climacteric fruits such as bananas, tomatoes, and apples. These fruits produce ethylene in increasing amounts as they ripen, and the presence of ethylene triggers a cascade of gene expression that leads to ripening processes such as softening, color change, and the conversion of starches to sugars.
If a mutant plant lacks the receptor for ethylene, it means that although ethylene might still be produced, the plant cells cannot perceive it or initiate the signaling pathway needed for ripening. The ethylene receptor is essential for detecting ethylene and activating the downstream responses. Without this receptor, the signal is effectively lost.
As a result, the fruit of such a mutant plant would fail to ripen properly. It might remain hard, green, and unpalatable for a much longer time, or potentially indefinitely, depending on the mutation’s severity. This type of mutation is somewhat analogous to a person having a sense organ (like the ear) missing — even if sound is present, it cannot be heard without the receptor.
This phenomenon has been studied in genetically modified or naturally occurring ethylene-insensitive mutants. For example, in tomatoes, the Never-ripe (Nr) mutant is known to be insensitive to ethylene due to a defective receptor, resulting in fruit that does not ripen normally even in the presence of ethylene.
In agriculture, manipulating ethylene sensitivity is useful. For instance, delaying ripening by reducing ethylene sensitivity helps prolong shelf life during transport. However, in nature, failure to ripen means seeds may not disperse effectively, since ripened fruit often attracts animals that aid in seed dispersal.