The primary characteristic that distinguishes fungi from plantae is the type of cell wall they possess. Fungi have cell walls made of chitin, whereas the cell walls of plants are primarily composed of cellulose.
This difference in cell wall composition reflects the distinct evolutionary paths and biological functions of these two kingdoms. Chitin, found in the exoskeletons of arthropods, provides a strong and flexible structure for fungi, allowing them to thrive in various environments, including soil and decaying organic matter. On the other hand, cellulose, produced by plants, provides rigidity and support, which are essential for their growth and development as multicellular organisms that perform photosynthesis.
Moreover, fungi and plants also differ in how they acquire nutrients. Fungi are heterotrophic organisms, meaning they obtain their food by absorbing nutrients from their surroundings, while plants are autotrophic and typically use photosynthesis to produce their own food from sunlight, carbon dioxide, and water. This fundamental difference in nutrition further emphasizes the distinct nature of these two kingdoms.