Q.What do the terms mycobiont and phycobiont signify in Lichens?

Lichen Symbiosis Components

Imagine a barren rock face, baking in the sun, freezing at night, with no soil in sight. Nothing grows there — except, sometimes, a crusty, coloured patch. That patch is a lichen. How does it survive where a plant cannot?

The answer is a partnership. A lichen is not a single organism. It is a symbiotic association — a living arrangement between two very different life forms: a fungus and an alga (or a cyanobacterium). The fungus provides the structure and protection; the alga provides the food. They live together as one functional unit, and neither could survive in that harsh place alone.

The Two Components

1. The Fungus (the Mycobiont) — This is the dominant partner, making up most of the lichen's bulk. It is usually an ascomycete fungus. The fungus weaves a dense network of thread-like cells (hyphae) that form the lichen's body (the thallus). Its job is to anchor the lichen to the surface, absorb water and minerals from the air and rain, and create a protective shield against UV radiation and drying out. The fungus cannot make its own food — it is heterotrophic.

2. The Alga or Cyanobacterium (the Photobiont) — This is the photosynthetic partner. It lives tucked inside the fungal mesh. Its job is to capture sunlight and carbon dioxide and produce sugars (carbohydrates) through photosynthesis. These sugars feed both itself and the fungus. The photobiont is autotrophic — it makes its own food, and the fungus lives off that food.

The Precise Statement …