Plant maintenance and environmental stress. Summarising the effects of contrasting elevation, soil, and latitude on Quercus ilex respiration rates

Abstract

Determining the increase in maintenance respiration in response to stress is critical for understanding the cost of adaptation, in terms of expenditure of assimilated carbon. Here, we ask how maintenance costs vary for populations native to contrasting habitats and whether maintenance cost remains constitutive or induced in response to stress. Two populations of Quercus ilex were selected in southern Iberian Peninsula, one growing close to the altitudinal limit and the other growing at mean elevations for the species. Maintenance respiration, growth, and structural variables were measured in leaves and fine roots. We modelled the results found here and those published for populations native to stressed (both soil and latitudinal) habitats. The maintenance respiration measured at 20 °C was higher in expanding (90 %) and in mature (35 %) leaves and in roots (78 %) of individuals growing at higher elevations. Furthermore, our meta-analysis supports that the cost of organ maintenance is higher in stressed habitats, irrespective of the stress factor. As regards the whole plant metabolic design, Q. ilex seems to combine high phenotypic plasticity according to current growth conditions, and high adaptive capacity for local differentiation in response to average stress conditions in the provenance habitat.