Development of experimental teaching material using lichens for understanding of symbiosis.

Abstract

The purpose of this study is the development of experimental teaching materials to confirm the symbiosis of lichens. Lichen is a symbiotic association of a fungus (mycobiont) and a photosynthetic partner (photobiont), which is a group of algae or cyanobacteria. The photobionts photosynthesize and provide the mycobionts with carbohydrates. In return, the mycobionts provide a stable environment for the photobionts. We developed experimental teaching materials to confirm that mycobionts provide a stable environment to photobionts. The mycobionts produce secondary metabolites. Some of them contained in the upper cortex of lichens absorbs ultraviolet light and protects photobionts from harmful ultraviolet rays. We used ethanol extract from the Flavoparmelia caperata (L.) Hale. We confirmed that the extract absorbed the ultraviolet wavelengths selectively (300 ～ 375nm) by using a spectrometer. Through algal culture experiment, we also confirmed the effect of usnic acid that absorbs UV rays. Furthermore, we have developed a cheap and easy experiment using a UV lamp or a colorless highlighter pen and a UV meter to determine the UV absorption of lichen's secondary metabolites. We can easily obtain lichen samples because they are no seasonal prevalence. Also, dried specimens can be used for experiments mentioned above. Therefore, lichens are very convenient to use for teaching materials.