The Influence of Temperature on a K+-Channel and on a Carrier-Type Transporter inNitella

Fisahn, J. and Hansen, U-P. 1986. The influence of temperature on a K⁺ -channel and on a carrier type transporter in Nilella—J. exp. Bot. 37. 440–460. In Nitella, the effects of temperature on membrane potential and on resistance consist of several components. The evaluation of their associated time-constants measured in linear(ized) temperature responses at a resting potential of–120 mV provides an approach to their identification. For changes slower than c. 1 s, the temperature effect on membrane potential and resistance does not originate from temperature action on the involved transporter, but is mediated by signals from temperature sensitive metabolic processes. In the case of potential, these processes seem to be identical to those which also mediate the light effect: pH-regulation, and two direct signals from photosynthesis, as indicated by the similarities of the related time-constants ($τ2,τ3=200±470-1s,τ1=540s,τ4=21s$ respectively). The temperature effect on resistance displays only one time-constant of 40 sin most experiments. The related process is unknown. The non-coincidence of the time-constants of the effect on potential and on resistance implies the involvement of a carrier-type transporter (H+-pump or cotransporter) in the effect on potential, and of a K+channel in the effect on resistance. The K+-channel is identified by the reversal potential of the effect on membrane potential measured in cells depolarized or hyperpolarized by an injected electrical current Under these conditions the temperature effect on resistance dominates the effect on potential.