Positive role of ethylene are as follows:

1. Breaking of dormancy : It breaks dormancy of storage organs.

3. Root initiation : In low concentration ethylene helps in root initiation, growth of lateral roots and root hairs.

4. Fruit ripening : It aids in ripening of fruits. C Ethylene is used to induce artificial ripening of these fruits e.g. Citrus, Apple, Mango, Banana etc.

5. Flowering : It stimulates flowering in pineapple and related plants though in other cases the gaseous hormone causes fading of flowers.

Negative role of Ethylene :

1. Growth : It inhibits longitudinal growth and stimulates transverse growth.

2. Senescence : It hastens the senescence of leaves and flowers.

3. Abscission : Abscission of various parts is stimulated by ethylene which induces the formation of hydrolases.

4. Apical dominance : Ethylene promotes apical domiance and prolongs dormancy of lateral buds.