Question

The most efficient precursor of ethylene
(a) Adenine
(b)Thiocarbamate
(c) Zeatin
(d) Methionine

Answer 1

The ethylene hormone helps when sprayed onto fruits to mature.

Complete answer: To solve this question, first, we should learn about plant growth regulators. For their growth and production plants need sun, water, oxygen, minerals and other nutrients. In addition to these external demands, plants often rely on certain organic compounds to signal, regulate and monitor plant growth. These are commonly referred to as plant growth regulators, or hormones for plant growth.

Now lets us find the solution from the given options-
1. Adenine, the nucleic acid precursor in intestinal cells that cannot synthesise purines de novo. So, Adenine is an incorrect answer.
2. Ethylene is a gaseous source of the plant hormone. It is formed by methionine breakdown and is present in all cells. Methionine is thus termed the precursor of ethylene hormone. So, Thiocarbamate is an incorrect answer.
3. Ethylene hormones help when sprayed onto fruit to mature. Ethylene hormone is found primarily in quickly dividing cells, and is normally in the dark caused by the actions of the precursor molecule, methionine. So, Zeatin is an incorrect answer.
4. In higher plants two pathways for ethylene biosynthesis were postulated. One refers to the dissolution of peroxidised linolenic acid and the other includes methionine degradation. A chemical mechanism was identified which accounts for such enzymatic ethylene formation. So, Methionine is the correct answer.

Thus, the correct answer is ‘Methionine’

Note: To assess the possible routes, the apple tissue was treated with radioactive linolenic acid and the required radioactive methionine analogues. None of these proposed ethylene precursors have been converted as successfully to ethylene as the methionine.