1. Auxins are growth promoting substances synthesized at meristematic regions of plants. 

2. The primary effect of auxin is cell enlargement and it stimulates growth of stem and root. 

3. Apical dominance – The phenomenon where growing apical bud inhibits the growth of lateral bud is apical dominance which is controlled by auxin synthesized at apical bud. 

4. Owing to activity of inducing multiplication of cells it is used in plant tissue culture to produce callus. 

5. Auxin stimulates formation of lateral and adventitious roots hence used for rooting propagation of cuttings.

6. 2, 4-D is a synthetic herbicide which kills dicot weeds. 

7. Induced parthenocarpy in fruitsoranges, banana, grapes, lemons is by application of auxin. 

8. Foliar spray of NAA and 2, 4-D induces flowering in litchi and pineapple. 

9. Premature fruit drop of apples, pear and oranges is prevented. 

10. Auxins break seed dormancy and promote germination. 

11. Auxins promote early differentiation of xylem and phloem, cell elongation, increase rate of respiration, prevent formation of abscission layer.