Final answer:
The direct consequence of an herbicide causing roots to shrivel and die is the shrinking and death of roots, leading to impaired water and nutrient absorption and potentially resulting in plant death. Option c is correct.
Step-by-step explanation:
An herbicide that causes roots to shrivel and die will have the most direct consequence of shrinking and death of roots, thereby impairing the plant's ability to absorb water and nutrients from the soil.
Given the functions of roots in plant physiology, the correct answer to the question 'An herbicide causes roots to shrivel and die. What is the most direct consequence for a plant treated with the herbicide?' is c) Shrinking and death of roots.
This loss of root function ultimately leads to the inability of the plant to sustain its growth and maintenance, resulting in the plant's poor health or death.