Hi Waqar Ul, Plant growth and morphogenesis is a complex process that takes place under a controlled environment. As it is a complex process, it requires a variable number of factors/growth regulators. The growth regulators are kind of managers (Transcription Factors) to control the laborers (Building blocks and their precursors) to build the plants. They also act at many different stages during the development to provide a perfect morphology.

Cheers,

Dharmesh

please elaborate your question. but, I would to add a point that PGRs can affect plant in a dose dependent manner which can be as a growth promoter or retardant.

Plant growth regulators affect plants in many ways, not just growth, morphogenesis but also development. Diferentiation is one of the processes which takes place in a plant and is also dependent on growth regulators. There are many plant growth regulators and they all affect plants in different ways. They may be regulators like auxin and cytokinin (its ratio determines whether it should be roots, shoots or callous cultures), however regulators may be like brassinoesteroids, (less "essential") which contributes to senescence. It may also be used for plant biotechnological processes and for agronomic/agricultural based activities. Forestry can be an example. There could be artificial growth regulators (mainly hormones) but it could be more substances.Hormones include , 2,4D, 2iP fro example.