Sundberg B, Ekblad A, Nasholm T, Palmqvist K
Lichen respiration in relation to active time, temperature, nitrogen and ergosterol concentrations
Functional Ecology: 1999 13:119-125
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 degrees 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.
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