Thermal acclimation of leaf respiration as a way to reduce source–sink imbalance at low temperatures in Erythronium americanum, a spring ephemeral

Many spring geophytes exhibit greater growth at colder than at warmer temperatures. Previous studies have suggested that there is less disequilibrium between source and sink activity at low temperature, which delays leaf senescence and leads to higher accumulation of biomass in the perennial organ. We hypothesize that dark respiration acclimates to temperature at both leaf and bulb level, mainly via the alternative pathway, as a way to reduce source-sink imbalance. Erythronium americanum was grown under three temperature regimes, 8/6 °C, 12/8 °C and 18/14 °C (day/night). Plant respiratory rates were measured at both growth and common temperature to determine whether differences were due to direct effects of temperature on respiratory rates or to acclimation. Leaf dark respiration exhibited homeostasis, which together with lower assimilation at low growth temperature, most likely reduced the quantity of C available for translocation to the bulb. No temperature acclimation was visible at the sink lev...