Bm. Clark et al., Characterization of mycobiont adaptations in the foliose lichen Xanthoparmelia chlorochroa (Parmeliaceae), AM J BOTANY, 88(10), 2001, pp. 1742-1749
A cross section of the vagrant soil lichen Xanthoparmelia chlorochroa was a
nalyzed using proton microprobe PIXE. Data were used to generate quantitati
ve, two-dimensional element distribution maps for Al, Si, P, S, Cl, K, Ca,
Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, and Sr. Element maps show differential elem
ent partitioning between the stratified lavers of the thallus. These data d
ocument transfer of inorganic nutrients across the thallus to the algal lav
er. Inorganic particle entrapment was also evident in the element maps. Den
se accumulations of calcium oxalate at the junction of the medulla and the
algal layer on the order of 10% by dry mass were discovered. Scanning elect
ron microscopy and thermogravimetric analyses were used to characterize the
calcium oxalate region. These data provide evidence for possible functiona
l roles of the calcium oxalate laver. including regulation of water and lig
ht. Data also provide support for a mutualistic interpretation of the liche
n association.