Hormone or growth regulators, also known as systematic herbicides, are typically absorbed through which part of the plant?

Systematic herbicides, often described as growth regulators or hormones, work effectively by being absorbed by specific parts of the plant and then translocating throughout the entire plant system. While systemic herbicides can technically be absorbed through various parts of the plant, the primary site of absorption is typically through the leaves.

Leaves have a large surface area and are specifically designed for gas exchange, which allows the herbicides to penetrate quickly into the plant's vascular system. This enables the chemicals to travel to other parts of the plant, affecting growth processes and leading to the desired herbicidal effect.

In certain scenarios, roots can also absorb some systemic herbicides, particularly those in the soil. However, for most systemic herbicides intended for broad-spectrum effectiveness and particularly for growth regulation, leaf absorption is crucial as it allows for rapid distribution throughout the plant.

Therefore, the understanding of how these systemic herbicides function and their absorption efficiency through the leaves shows why this option is the most applicable, reinforcing the concept of plant physiology and the mechanism of action of these herbicide types.