substrate (noun, pl. substrates;ecology term,Substrate term; variant spelling: sl. substratum, pl. substrata) – a surface or underlying layer on which an organism grows or to which it is attached. Some treatments prefer the distinction between substrate and substratum: (1) substrate (commonly used in mycology & microbiology, but also on lichenology) – an organic material like detritus inhabited by the organism and providing nutrients as well as some structural support; (2) substratum (commonly used in lichenology) – a surface or underlying layer which provides structural but no or only limited nutritional support. Problem with this concept: The distinction between substrate/substratum is arbitrary. A lichen growing endosubstratic inside the bark of a tree may or may not derive some of its nutrients from that tree. Many saxicolous lichen incorporate mineral grains within their thalli and probably derive at least some of their nutrients as inorganic solutes from weathering processes. Phytopathogenic fungi depend not only on the nutritional, but also the structural support of the plant they infest.