Final answer:
Sensitive fern and ragweed are two plants that could cause photosensitization in horses.
Step-by-step explanation:
Two plants that could cause photosensitization in horses are sensitive fern and ragweed. Photosensitization is a condition in which the skin becomes overly sensitive to sunlight, resulting in inflammation and damage. These plants contain compounds that can react with sunlight and cause an abnormal skin response in horses. It is important to be aware of these plants and prevent horses from eating them to avoid photosensitization.