摘要：Respiration rates, thermal sensitivity, and thermal acclimation potential of root respiration were investigated in Ranunculus from the Arctic. Comparisons of three species ( R. glacialis , R. nivalis and R. acris subsp. pumilus ) used plants grown on a mountain or in a glasshouse for 6 wk at contrasting soil temperatures (5.4 and 14.5°C, respectively). Northern and southern ecotypes of two species of Ranunculus ( R. pygmaeus , and R. acris subsp. acris ), together ranging from Svalbard (79 °N) to Scotland (56°N), were similarly compared after 2 wk in a growth cabinet at 5 and 15°C. Respiration rates varied at standard measurement temperatures; R. nivalis and R. pygmaeus grown on the mountain or at 5°C had the highest respiration, followed by other alpine snowbed species ( R. glacialis and R. acris subsp. pumilus ) and R. acris subsp. acris from the arctic lowland; R. acris subsp. acris from Scotland had lowest rates. Respiration was temperature sensitive for all populations, increasing progressively between 5 and 20°C (Q 10 (5–15) : 1.2–2.4). Extent and type of acclimation of root respiration varied with no clear latitudinal pattern emerging. Acclimation to a 10°C increase in growth temperature was achieved through: change in temperature sensitivity (shown by changes in Q 10 (5–15) values) ( R. acris subsp. pumilus ); or reduction in absolute rates ( R. pygmaeus from Svalbard, R. acris subsp. pumilus and R. nivalis ). Complete acclimation occurred in R. acris subsp. pumilus and R. pygmaeus , whereas R. acris subsp. acris from Scotland and R. glacialis did not acclimate. Plants that adjust root respiration (e.g., R. pygmaeus from Svalbard and R. acris subsp. pumilus ) to maintain a positive carbon balance, may tolerate predicted temperature increases in arctic regions. Plants with high rates of root respiration and/ or high sensitivity to temperature as well as poor acclimation potential, (e.g., R. glacialis ) may only persist in cold microhabitats.
