Rapid acclimation of root hydraulic conductivity to low temperature

Root hydraulic conductance of many species is substantially reduced by exposure to low temperatures. The objective of this research was to investigate the decrease and recovery of root hydraulic conductivity in spinach (Spinacia oleracea L.) root systems upon exposure to low temperature, Root hydraulic conductivity (Lp) was determined for detached whole root systems as the slope of the flux and an applied pressure gradient. Water flux (Jv), of root systems grown at 20 degrees C, decreased immediately upon exposure to 5 degrees C, After 2-5 h Jv recovered and reached a stable value after 12 h exposure to 5 degrees C. In separate experiments, the root Lp of plants acclimated for 7 d at 5 degrees C was 125% greater than that of isolated root systems acclimated for 12 h at 5 degrees C. Lp of plants grown and measured at 5 degrees C was about 50% of the Lp of plants grown and measured at 20 degrees C, The rapid acclimation to low temperatures observed in detopped root systems was also indicated in intact plants at 20/5 degrees C (shoot/root temperatures) using mass flow porometry, Acclimation of the root system after exposure to 5 degrees C was apparent by recovery of stomatal opening. These results indicate that spinach root systems have the ability to acclimate rapidly to changes in temperature and to continue acclimating during prolonged exposure to low temperature.