What effect do plant growth regulators have on treated plants?

Plant growth regulators are substances that influence the growth processes of plants. The correct choice highlights that these regulators can lead to stunted and compact growth in treated plants. This means that when applied, plant growth regulators can inhibit certain hormonal processes that encourage elongation and expansion, resulting in shorter and denser plant forms.

This specific effect is particularly useful in situations where growth control is desired, such as in ornamental horticulture, where compact plants may be more aesthetically pleasing or easier to manage.

While other options mention effects that some growth regulators can have, such as promoting rapid growth or enhancing flowering, they do not accurately describe the typical outcome of the class of regulators that primarily cause stunted growth. Similarly, the acceleration of fruit ripening is not a consistent effect attributed to growth regulators in general; rather, specific types may promote this aspect but are not the primary focus of the question. Thus, the understanding of plant growth regulators as means to create stunted and compact growth is foundational to their application in horticulture and agriculture.