1. Propagation:

They are applied in the form of paste and solution. The concentration of the chemical varies with plant species and types of cutting and method of application. Rooting hormones are IAA, IBA, and NAA.

a) Soak Method:

10 to 100 ppm for 12 -24 hrs called the soak method.

b) Quick Dip Method:           

1000 to 5000 ppm for 5 seconds. Some P.G.R is used in layering, grafting, and budding for getting high success.

2. Seed Germination:

GA₃ significantly accelerates seed germination in many plant species. Pre-soaking the seed with GA₃. Such as okra and sugar beet increase germination.

3. Induction of Flowering:

Plant growth regulators like NAA at 10 to 50 ppm cause early flowering in pineapple. 2, 4 D at 6 to 10 ppm has been used to induce flowering in pineapple. Flowering can be delayed by 1 to 2 weeks NAA at 200 to 800 ppm application in apple, cherries, pears, peaches, and plums.

4. Sex Expression:

Plant growth regulators can change the sex of the flowers. Male sterility can be induced in corn by MH (malic hydrazide). It is used in plant breeding for the induction of male sterility. Application of NAA, IAA, and GA at 50 to 100 ppm increases female flowers in pumpkin, cucumber to get more yield.

5. Flower and Fruit Thinning:

Many fruit trees produce heavy flowering and fruit in one year and few or one in the next year. By using G.R the normal bearing can be maintained NAA at 5 to 10 ppm and NAA at 5 to 7 ppm for thinning of apple, peaches, and grapes.

6. Pre Harvest Drop of Fruits:

Flower and fruit drop is a problem in many fruit crops. Application of NAA 10- 50 ppm in mango, citrus, and chilies reduce fruit drop by preventing the formation of the abscission layer.

7. Fruit Development:

Application of 50- 100 ppm GA in grapes increases the berry size.

8. Early Maturity:

Early maturity fetches higher prices in the market. In pineapple application of 20 ppm, NAA induces early flowering and early maturing at least by two months. Spraying of 50 ppm NAA reduces maturity in grapes, use of 250 – 400 ppm of Ethrel induces early maturity in Ber.

9. Early Ripening and Colour Development:

Fruits like mango, banana, papaya ripes after harvest. Dipping of fruits in 20-50 ppm Ethrel solution induces golden yellow colour to fruit induces early maturity.

10. Delayed Maturity:

Delay in ripening is required when fruit are to be sent to long-distance market. Dipping of fruit in 2,4-D, 2,4- 5- T, or MH- 40 extends the storage life of fruits.

11. Sprouting of Bud:

Ethrel, GA, thiourea, IBA and Cyotkininn, spray induces sprouting of buds.

12. Braking of Dormancy:

GA, Ethrel, NA are used in breaking dormancy in seeds and buds.