and one to two sentences identify the purpose of the roots in a plant and how a disease that harms the root of the flowering plant would affect the plant's ability to survive

The purpose of roots in a plant is to anchor it in the soil, absorb water and nutrients, and provide support for the above-ground parts of the plant. If a disease harms the roots of a flowering plant, it would severely hinder the plant's ability to absorb water and nutrients, leading to nutrient deficiency, wilting, stunted growth, and ultimately, the plant's inability to survive.