Cycloheximide inhibits root water flow and stomatal conductance in aspen (Populus tremuloides) seedlings

Abstract

Aspen (Populus tremuloides Michx.) roots were treated with cycloheximide, a protein synthesis inhibitor, to examine the role of protein synthesis in root water transport and plant water relations. Within less than 30 min following root application, cycloheximide inhibited steady-state root water flow rates and 1 h after the application of 1 mM cycloheximide, root hydraulic conductivity had decreased by 85% compared with control roots. However, stomatal conductance showed a significant inhibition only after 2 h following cycloheximide treatment. The reduction in root hydraulic conductivity was accompanied by an almost three-fold increase in the apoplastic water flow ratio as determined by the trisodium 3-hydroxy-5,8,10-pyrene-sulphonate tracer dye. Cycloheximide-treated roots showed a decrease in the immunostaining intensity of a 32 kDa microsomal protein band that immunoreacted with the AnthPIP1; 1 antibody suggesting a decrease in the membrane aquaporin expression. These changes occurred without severe metabolic disruptions as measured by root respiration. The results point to the importance of protein-mediated transport in roots and the rapidity of response suggests that protein synthesis may be used as a principal regulatory mechanism in root water transport in aspen.