|MadSci Network: Botany|
You have realized a key component underlying the symbiotic nature of lichens. As explained in the Lichen Biology tutorial from the Univ. of Sydney School of Biological Sciences:
In general terms, the photobiont (cyanobacteria, algae) supplies the association organic carbon from photosynthesis, and the mycobiont (fungi) ensures protection and supply of minerals & water.....Most commonly, photobionts are located in a layer within the fungal tissue. The layer is generally oriented in a manner that maximizes photosynthesis, and is protected from rapid changes in water availability.
Reproduction of lichens is a bit more complex, but another fascinating symbiotic adaptation as well. As explained in the Lichen Biology tutorial:
Sexual reproduction tends to result in fungal and algal propagules that following germination must meet with a compatible partner before a functional lichen can form. Sexual reproduction is not considered to be a common means of reproduction to form new units. However, propagules may become entangled with an existing lichen. By initiating growth within an existing matrix, genetic complexity may be added to the unit.
Asexual reproduction through diaspores known as soredia or isidia seems to be much more prevalent, as described in the Lichen Biology tutorial. Please see Lichen Life History & Ecology, from the UC Museum of Paleontology @ Berkeley, or Information about Lichens, from the BioNet Europe Project, for more information on lichen reproduction as well as other aspects of these amazing organisms.
Thanks for the great questions!
Jeff Buzby, Ph.D.
CHOC Research Institute
Try the links in the MadSci Library for more information on Botany.