What symptom is an early indication of the presence of certain growth regulators?

The presence of certain growth regulators can lead to abnormal growth patterns, particularly in the way that plant shoot tips develop. An early indication of this influence is often noted by the abnormal bending or twisting of shoot tips. Growth regulators can alter the normal patterns of plant hormone activity, causing the cells at the tips to respond in ways that result in these distinctive physical changes.

In contrast, the other symptoms listed, while they can indicate various plant stress factors or issues, do not specifically relate to the early effects of growth regulators. Stunted growth might suggest nutrient deficiencies or diseases, rapid wilting could indicate water stress, and yellowing of leaf margins is typically associated with nutrient imbalances. However, the twisting or bending of shoots is a hallmark sign directly associated with the influence of growth regulators on plant morphology.