Which of the following processes is NOT affected by herbicidal activity?

The correct choice is that water absorption is not directly affected by herbicidal activity. Herbicides primarily target specific physiological processes within plants such as cell division, tissue development, and respiration.

Herbicides can disrupt cellular functions and metabolic pathways that are crucial for growth and development. For instance, many herbicides inhibit processes such as photosynthesis, which ultimately impacts respiration and energy usage in the plant. Cell division and tissue development are also vital functions that herbicides can interfere with, leading to stunted growth or plant death.

In contrast, water absorption typically involves the plant's root system and its interaction with soil moisture, which is generally not the primary target of herbicides. While herbicidal activity can inhibit overall plant health and indirectly affect water uptake (due to root damage or reduced leaf area), the process of absorbing water itself remains unaffected in a direct manner by the action of herbicides. This distinction makes it clear why water absorption is the correct answer in this context.