Answer: Ethylene
Ethylene is a hydrocarbon gas which is produced naturally by the combustion process. It is produced in plants at the time of fruit and flower ripening. It is a plant hormone which is responsible for the changes that occur during the ripening process of the fruits or flowers these includes changes in the color, texture, softening and other process that helps in the maturation. Apples and pears are the plants which produce ethylene for ripening but exceptionally their are plants which do not produce ethylene for ripening these includes cherries and berries.