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How do fungi obtain nutrients without photosynthesis?

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Two Amanita pantherina mushrooms with brown caps covered in white spots grow among moss and fallen leaves. — fungus A pair of panther cap mushrooms (*Amanita pantherina*). Closely related to the death cap mushroom (*Amanita phalloides*), the panther cap is highly poisonous.

Fungi are heterotrophic organisms that lack the ability to perform photosynthesis, meaning they must obtain their nutrients from external organic sources. They achieve this primarily through a process known as osmotrophic nutrition, which involves extracellular digestion.12

To feed, fungi secrete digestive enzymes onto their food source, such as dead organic material or living host tissues. These enzymes break down complex molecules like carbohydrates and proteins into smaller, simpler units that can be absorbed directly through the walls of the fungal hyphae.12

Depending on their ecological role, fungi obtain these nutrients in different ways:
* Saprotrophic fungi decompose dead organic matter, playing a vital role in nutrient cycling.1
* Parasitic fungi invade living organisms, such as plants or insects, to extract nourishment from their cells. Some parasites use specialized absorptive structures called haustoria to penetrate host tissues and absorb nutrients directly.13
* Symbiotic fungi, such as those found in lichens, often exchange nutrients with photosynthetic partners like algae, receiving carbohydrates in return for other substances.4