Synthesis of the cortical dibenzofuran derivative usnic acid and the medullary depsidone salazinic acid was studied in Xanthoparmelia stenophylla thalli from which the compounds had been removed by acetone rinsing prior to a 21-day field experiment with UV absorbing and transmitting screens. Natural levels of ultraviolet radiation clearly induced the re-synthesis of usnic acid. The resynthesis was boosted by the addition of ribitol, the carbohydrate delivered from the Trebouxia photobiont to the mycobiont. Salazinic acid was also weakly induced by UV. Re-synthesis was relatively low, up to 2.5 and 3.1% of start values for usnic and salazinic acid, respectively. However, given that the natural content of both compounds was high, constituting 12% of thallus dry weight, the absolute amounts of lichen compounds re-synthesised were not so small. We also studied the extractability of nine extracellular lichen compounds in three species X. stenophylla, Hypogymnia tubulosa, and Vulpicida pinastri, and found two distinct fractions of cortical compounds, one major that was completely extractable from living lichens and one minor that was only extractable with grinding. Medullary compounds were completely extracted without grinding. These findings did not influence the relative differences between treatments in our experiment, but may be of importance for future assessments of, e.g., quantitative studies of extracellular lichen compounds.

Summary• This study analysed relationships between secondary chemistry, lichen growth rates and external habitat factors for two groups of UV-B-absorbing secondary compounds in the lichen Lobaria pulmonaria in order to test some hypotheses on their formation and function.• Medullary depsidones and cortical melanins were quantified in thalli transplanted to three successional forest stands (shaded young forest, open old forest, sunexposed clear-cut area) and subjected to different watering regimes (spraying with water, water + nitrogen, no spraying). Growth rates were already known.• The total concentration of all seven depsidones was constant across the entire range of growth rates and sun exposures, showing that these depsidones serve functions other than photoprotection. Thalli from the well-lit transplantation sites had the highest synthesis of melanins. Within each forest type there was a trade-off between growth and melanin synthesis. Melanins and photosynthetic acclimation enhanced survival on a subsequent exposure to high light intensity, despite excessive temperatures resulting from higher absorption of solar energy in melanic thalli relative to pale thalli.• In conclusion, the highly responsive melanic pigments play a photoprotective role in light acclimation, whereas the constant amount of depsidones across a wide spectrum of growth ranges and irradiances is consistent with herbivore defence functions.

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We investigated 56 newly presenting Type 2 diabetics who were significantly overweight (BMI >27.0). Patients were given standard management and observed for a six month period. They were then divided into ‘good weight losers’ (13 patients who lost 10% or more of initial body weight) and ‘poor weight losers’ (19 patients who lost 3% or less of initial body weight). When the two groups were compared, there was no dimrence in age, sex ratio, initial body weight, marital status, sociai class, smoking, drinking, exercise and use of oral hypoglycaemic agents. Good weight losers, however, had significantly more visits to clinic (4.0 ± 1.0 v. 3.1 ± 1.1, p<0.05), and particularly to the dietitian (5.2 ± 2.3 v. 2.9 ± 1.2, p<0.005) during the six month period. Obese Type 2 diabetics should thus ideally see dietitians on a monthly basis during the immediate post‐diagnosis period.

Lichens are colourful organisms owing to numerous combinations of algal and fungal pigments (as reviewed by Rikkinen 1995). Colour is often used in taxonomic studies to aid species identification but it is sometimes over-used as a characteristic to discriminate related genera such as, Xanthoparmelia and Neofuscelia (Poelt & Leuckert 1993). However, colour variations within species can be significant (Solhaug et al. 2003) because of spatial (Gauslaa & Solhaug 2001; Gauslaa & Ustvedt 2003) and temporal variations (Gauslaa & McEvoy 2005) in environmental factors. There are few experimental studies on lichen colours so far; as a result we do not know the relative importance of genetic versus environmental factors. Our study aimed to assess the effect of ultraviolet radiation (UVR) on the colour of the widespread foliose lichen Xanthoparmelia stenophylla (Ach.) Ahti & D. Hawksw. (until recently known as X. somloensis (Gyeln.) Hale, see Ahti & Hawksworth 2005). Usnic acid is responsible for the yellowish appearance of its upper cortex, but other colour variations are also mentioned in taxonomic literature (Brodo et al. 2001). More specifically, we wanted to discover if UVR and the photosynthate ribitol supplied by the photobiont would cause changes in pigmentation in a Xanthoparmelia species. These factors have been shown to induce and stimulate the synthesis of the orange parietin in Xanthoria parietina (Solhaug & Gauslaa 2004; Solhaug et al. 2003).