Chemical strains

Thamnolia vermicularis is an arctic-alpine, fruticose, soil-dwelling lichen that enjoys a very wide distribution. The species consists of two chemical strains, one predominantly found in the Northern Hemisphere and the other in the Southern Hemisphere, with most populations from intermediate regions exhibiting intermediate chemical types. Sato (1965) showed that the southern strain accumulates thamnolic acid [403], whereas the northern strain is characterized by two compounds, squamatic acid [404] and baeomycic acid [405]. Populations from Greenland, Novaya Zemlya, and Svalbard exhibited only the northern profile. Two populations from South America exhibited only the southern type, while collections from New Zealand showed nearly pure southern type. 

Culberson, C. E. 1965. A note on the chemical strains of Parmelia furfuracea. Bryologist 68 435 39. 

Karasawa D, Shimizu S, Mentha candicans, a new chemical strain of section Spi-catae, containing tntwr-sabinene hydrate as the principal component of essential oil, Agric Biol Chem 42 433 37, 1978. 

The major Poisson s ratio is vl2 and E = E2/El is the ratio of the transverse to longitudinal modulus. Equation 8.24 gives the induced curvature for anticlastic deformation of an unsymmetric cross-ply laminate. The curvature is dependent on the thermal and chemical strain mismatch (e, — e2), lamina mechanical properties (v12, E) and the half-thickness, h. 

The nonacyclic diketopiperazine derivatives scabrosin 4,4"-diacetate (13), scabrosin 4-acetate-4 -butyrate (14), scabrosin 4,4 -dibutyrate (15) and scabrosin 4-acetate-4 -hexanoate (16) have been isolated from a chemical strain of Parmelia scabrosa by Begg, Elix, and Jones (14). 

Yosioka and co-workers (338) isolated the known depsidone vicanicin (292) from a Caloplaca species. They were unable to obtain an authentic sample so they confirmed structure (292) by spectroscopy and by subjecting the ethyl ether (389) to the nitric acid oxidation technique of Dean et al. 98) which afforded the identifiable fragments (392) and (393) (Scheme 48). Sargent and Elix and their co-workers 288) isolated vicanicin (292) from Psoroma sphinctrinum another chemical strain produced norvicanicin (391), also available by boron tribromide induced demethylation of vicanicin (292). Vicanicin was synthesized 276) from the benzophenone (394) which on oxidation afforded the grisadienedione converted by exposure to base or add into the depsidone (395) and thence by chlorination into vicanicin (292). 

Acetylleucotylin (489) and 20a-acetoxy-6a,22-dihydroxyhopane (490) were isolated from chemical strains of Physcia aipolia (134). The structures of these products were determined primarily from their C-n.m.r. spectra. The compound with the C-20 acetoxy group is of particular interest as it is the first example of a hopane triterpenoid with an oxygen substituent in this position. 

Many properties enable the lichens to be extremists, but they are sensitive to other environmental conditions and in some respects even more so than other plants. It would be as unreasonable to consider all lichens as extremists, as it would be unreasonable to regard them all as cosmopolitan because even the widely distributed species are split into different races and chemical strains. When we know more about taxonomical differentiation with regard to ecotypes (Culberson, 1970) the ways of ecological and physiological adaptation will be more easily understood. 

Hale, M. E., Jr. (1963). Populations of chemical strains in the lichen Cetraria ciliaris. Brittonia 15,126-133. 

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