Plants that are resistant to fungal, bacterial, or viral diseases generally owe this resistance to what is known as the hypersensitive response. Cells around the site of infection die, preventing the spread of the pathogen by depriving it of nutrients. Some of the cells produce phytoalexins and other chemicals before they die. The dead tissue, called a necrotic lesion, contains and isolates what is left of the microbial invasion (Figure 40.2). The rest of the plant remains free of the infecting microbe.
One of the defensive chemicals produced during the hypersensitive response is a close relative of aspirin. Since ancient times, people in Asia, Europe, and the Americas have used willow (Salix) leaves and bark to relieve pain and fever. The active ingredient in willow is salicylic acid, the same substance from which aspirin is derived.
Was this article helpful?
This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.