Jäkäläkasvustot

Jäkäläkasvustot, commonly known as lichens, are composite organisms that arise from algae or cyanobacteria living among filaments of multiple fungi species in a mutually beneficial symbiotic relationship. The lichen organism is not a single entity but rather a symbiotic partnership. The fungus provides structure and protection to the algae or cyanobacteria, which in turn produce food for the fungus through photosynthesis.

Lichens exhibit a remarkable diversity of forms and are found in almost every terrestrial environment, from the aridest deserts to the frozen tundras, and even on exposed rocks and branches. Their growth forms are typically categorized into three main types: crustose, which are tightly attached to the substrate, foliose, which are leaf-like and can be peeled off, and fruticose, which are shrub-like or hanging.

These organisms play important ecological roles. They are primary colonizers of bare rock, initiating soil formation. Lichens also serve as a food source for various animals, including reindeer and insects. Furthermore, their sensitivity to air pollution makes them valuable bioindicators, with their presence, absence, or condition reflecting the quality of the surrounding air. The study of lichens is known as lichenology.