BIOL 2P96 Lecture Notes - Lecture 6: Trichomonas, Marchantiophyta, Lateral Root
28 Jul 2015
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Symbiotic association btw fungus (mycobiont) and alga or cyanobacterium (photobiont) Unique to that species, otherwise unknown in nature (does not survive very well w/o symbiont) Many change shape & fine structure in symbiosis compared to free-living so must be cultured for id. Loosely attached to substrate by root like rhizines or central stalk-like umbilicus. Same algal sp. can form lichens w/ different fungal partners. One fungus can form lichens w/ variety of algal spp. Different photobionts at different stages of the life cycle. Mycobiont determines lichen morphology: lichens are named by mycobiont. Form upright thallus attached to substrate by holdfast thick outer cortex, medulla and distinct algal layers. Mycobiont adequate illumination facilitate the gas exchange of their photobiont cell population compete for space above ground. * water and dissolved mineral nutrients taken up by cortical layer. Protects photobiont from desiccation lichen pigments hyphae are covered by a mainly proteinaceous, hydrophobic cell wall surface layer.
