Step 3: Analyze the function of each option:
- Xylem: Responsible for transporting water and nutrients from roots to other parts of the plant. It does not directly prevent drying out or protect against microbes.
- Cuticle: A waxy layer covering the surface of leaves and stems, which reduces water loss and acts as a barrier against microbial invasion.
- Stomata: Pores on the leaf surface that regulate gas exchange and water vapor release, but they do not directly prevent drying out or protect against microbes.
- Chloroplast: Organelles responsible for photosynthesis, not related to water retention or microbial protection.