Coordinated responses of leaf and absorptive root traits under elevated CO2 concentration in temperate woody and herbaceous species

Abstract

Elevated atmospheric CO2 concentration (e[CO2]) profoundly affects the growth and physiological activities of plants. However, the responses of leaf and root functional traits to e[CO2] are rarely investigated together, limiting our understanding of the whole-plant adaptive strategies to climate change. In this study, 17 temperate woody (nine) and herbaceous (eight) plant species were grown under ambient [CO2] (a[CO2], 380 ppm) and e[CO2] (720 ppm) conditions in the chamber (Percival Scientific, Perry, USA), and the responses of 16 key functional traits (anatomy, morphology, physiology) of leaves and typical absorptive roots (the 1st order root) and their relationships were studied. Averagely, we found that e[CO2] increased leaf thickness (LT, +13 %), reduced specific leaf area (SLA, -14 %), increased palisade tissue thickness (PT, +23 %) and the ratio of palisade tissue to spongy tissue thickness (P/S, +14 %) across species, which were accompanied by physiological changes. For absorptive root, root diameter (RD) increased by 15 %, specific root length (SRL) decreased by 12 %, and root tissue density (RTD) decreased by 14 % across species under e[CO2], indicating that plants tend to construct thicker roots with looser tissue under e[CO2] compared to a[CO2]. Also root cortical thickness (CT) and the ratio of cortical thickness to stele radius (C/S) increased by 20 % and 13 % under e[CO2], respectively, implying an increase in root potential absorption capacity. More importantly, the corresponding functional traits of leaf and absorptive root, i.e., LT and RD, SLA and SRL, PT and CT, P/S and C/S, showed positive correlations in their magnitudes of the responses to e[CO2] in both woody and herbaceous species. Our study revealed the coordinated changes of corresponding functional traits in leaf and absorptive root under e[CO2] condition, which provide some insights into the whole-plant resources acquisition strategy under changing environment.