Adaptation of malate dehydrogenase to environmental temperature variability in two populations of Potentilla glandulosa Lindl.

Summary The responses of the kinetic properties of malate dehydrogenase to environmental temperature variability were compared for two populations of Potentilla glandulosa (Rosaceae). The two populations are native to regions of contrasting climates, with the inland population experiencing a high level of temperature variability during growth and the coastal populaton a low level of temperature variability. The substrate binding ability, as measured by apparent K_m of both populations was relatively insensitive to assay temperature (Q₁₀<2.0) over the range of temperatures likely to be encountered during growth. The breadth of this thermal optimum was different for the two populations with the K_m of the inland plants exhibiting relative temperature insensitivity over a much wider range of temperatures than the K_m of the coastal plants. There was no difference between the two populations in the thermal stability of MDH activity.