What characterizes a plant growth regulator herbicide?

A plant growth regulator herbicide is primarily characterized by its ability to induce abnormal tissue development in plants. These herbicides manipulate the hormonal balance within plants, which can lead to undesirable growth patterns. For instance, they may cause excessive elongation of stems or leaf distortion, which ultimately affects the plant's health and competitiveness.

The mode of action of these herbicides often involves interfering with the normal physiological processes that regulate plant growth, allowing for targeted suppression of unwanted vegetation, such as invasive or troublesome aquatic plants. This is particularly beneficial in managing populations in aquatic systems where maintaining the ecological balance is crucial.

In contrast, the other choices represent functions that are not characteristic of plant growth regulator herbicides. Enhancing root growth, promoting flowering, or entirely preventing plant growth do not align with the core function of this category of herbicides, which is to modify growth patterns and behaviors instead.