The effect of temperature on Antarctic lichen cytochrome and alternative respiratory pathway rates

Abstract

Respiration is a crucial process that provides all living organisms with energy and metabolites for growth and cellular maintenance. The processes that control respiration in lichens remain poorly understood. We investigated the effects of short-term temperature changes on the respiration rate, as well as the relative contributions of the cytochrome and alternative pathways of thalli from four green-algal lichen species collected from their natural habitats in Antarctica. Lichen respiration was sensitive to short-term temperature increases over a range of 5–35 °C. The total O2 uptake rate was increased by fourfold, and the mean respiratory coefficient (Q10) decreased from 2.5 to 1.3 as the temperature increased. An increase in temperature from 5 to 15 °C had a positive effect on cytochrome respiration coupled with energy production. Temperatures above 15 °C stimulated the activation of the alternative (energy-dissipating) respiratory pathway. Hyperthermia led to increased O2 consumption that was not associated with mitochondrial oxidases. The effects of increased temperature on the respiration rates were more pronounced in the bipolar lichens Umbilicaria decussata and Usnea sphacelata than in the Usnea aurantiaco-atra species with a narrower geographical distribution.