Relations between irradiance (I) and lichen growth were investigated for five macro-lichens growing at two sites in Sweden. The lichens represented different mycobiontphotobiont associations, two morphologies (foliose, fruticose) and two life forms (epiphytic, terricolous). The lichens were transplanted at two geographically distant sites in Sweden (1000 km apart) from Sept 1995 to Sept 1996 in their typical microhabitats, where microclimate and growth were followed. Between April/May and Sept 96, the terricolous species had a dry matter gain of 0·2 to 0·4 g (g DW) -1 and the epiphytes 0·01 to 0·02 g (g DW) -1 . When related to area, growth amounted to 30 to 70 g m --2 for the terricolous species and to 1 to 4 g m --2 for the epiphytes. There was a strong correlation between growth and intercepted irradiance when the lichens were wet (I wet ), with 0·2 to 1·1 g lichen dry matter being produced per MJ solar energy. Across the 10 sets of transplants, light use efficiencies of dry matter yield (e) ranged between 0·5 and 2%, using an energy equivalent of 17·5 kJ g --1 of lichen dry matter. The higher productivity of the terricolous species was due to longer periods with thallus water contents sufficient for metabolic activity and because of the higher mean photon flux densities of their microhabitat. A fourfold difference in photosynthetic capacity among the species was also important. It is concluded that lichen dry matter gain was primarily related to net carbon gain during metabolically active periods, which was determined by light duration, photon flux density and photosynthetic capacity.

Summary 1.Respiration in eight lichen species was related to thallus hydration status, external temperature and to total nitrogen, chitin and ergosterol concentrations. Chitin is a nitrogenous and major compound of the fungal cell wall, and ergosterol is a sterol of the plasma membrane in fungi and sometimes in algae. 2. Hydration of previously dry thalli resulted in an initially high rate of respiration. Both the amplitude of this resaturation respiration and the time required to reach steady state varied among species. Generally, peak rates were one to three times higher than steady-state rates, which were reached 3-7 h after hydration. 3. Increases in external temperature also resulted in transient bursts in respiration. Again, both the amplitude of the burst and the time required to reach steady state varied among species. Also depending on species, a temperature increase from 5 to 15°C resulted in two-to fivefold increases in steady-state respiration. 4. Steady-state respiration, at optimal thallus hydration and a given temperature, varied three-to sixfold among the species, when related to thallus dry mass. This difference correlated best (r 2 = 0·89) with their ergosterol concentration, where a doubling in ergosterol resulted in more than a doubling in respiration. Respiration correlated less well to total nitrogen or chitin. 5. The chitin to ergosterol ratio varied more than one order of magnitude between the species, where species with high nitrogen concentrations had the highest ratio. This implies that species with access to ample amounts of nitrogen can make more fungal cell walls in relation to plasma membrane surface area.

Relationships between growth, nitrogen and concentration of unique biont components were investigated for the tripartite lichens Nephroma arcticum (L.) Torss. and Peltigera aphthosa (L.) Willd. Nitrogen availability was manipulated during 4 summer months by removing cephalodia and their associated N 2 fixation activity, or by weekly irrigation with NH 4 NO 3 . Chlorophyll and ribulose 1·5-biphosphate carboxylase/oxygenase (Rubisco), and chitin and ergosterol were used as photobiont and mycobiont markers, respectively. Nitrogen concentrations were similar in older and newer parts of the same thallus, varying between 2 and 5 g m -2 , with P. aphthosa having higher concentrations than N. arcticum. Both chlorophyll (Chl a) and chitin were linearly correlated with thallus N, but N. arcticum invested more in fungal biomass and had lower Chl a concentrations in comparison with P. aphthosa at equal thallus N. During the 4 months, control and Nfertilized thalli of N. arcticum increased in area by 0·2 m 2 m -2 and P. aphthosa by 0·4 m 2 m -2 . Thallus expansion was significantly inhibited in samples without cephalodia, but there was no effect on lichen weight gain. Mean relative growth rate (RGR; mg g -1 d -1 ) was 3·8 for N. arcticum and 8·4 for P. aphthosa, when time (d) reflected the lichen wet periods. RGR was 2-3 times lower when based on the whole time, i.e. when including dry periods. The efficiency (e) of converting incident irradiance into lichen biomass was positively and linearly correlated with thallus Chl a concentration to the same extent in both species. The slower growth rates of N. arcticum, in comparison with P. aphthosa, could then be explained by their lower nitrogen and Chl a concentrations and a subsequently lower light energy conversion efficiency. Functional and dynamic aspects of resource allocation patterns of the two lichens are discussed in relation to the above findings.

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The aim of this study is to explore how cultural factors interact with preschool teachers' shaping of activities with science content, and also how Activity Theory (AT) as a theoretical framework can be useful for examining interrelations within preschool systems. Qualitative data was collected from three preschools in the form of guided group discussions with preschool teachers, observations and video recordings of activities, and stimulated recall discussions based on the recorded practices. The preschools displayed diverse approaches for experiencing and learning science, some with great creativity. In all preschools learning was integrated with care, upbringing and play. To support children's interest and confidence was central. How science activities were shaped mainly depended on how children's interests were allowed to govern practice. The use of AT as an analytical tool was proven to be effective in identifying the elements, relationships and tensions crucial for understanding the framing of science activities.