Influence of Helminthosporium maydis, Race T, Toxin on Potassium Uptake in Maize Roots: II. Sensitivity of Development of the Augmented Uptake Potential to Toxin and Inhibitors of Protein Synthesis.

Basal K(+) uptake in the root midzone region (cm 2 + 3 + 4) of N and T cytoplasmic versions of each of four maize inbreds was equally sensitive to the toxin(s) of Helminthosporium maydis, race T. Basal K(+) uptake in the root apex (0-1 cm) and augmented K(+) uptake in the root midzone were more toxin-sensitive in inbreds W64A(T) and Mo17(T) than in inbreds W64A(N) and Mo17(N). This differential response of N and T cytoplasms to toxins was not found for corresponding cytoplasms of inbreds WF9 and B37.Development of the augmented K(+) uptake rate in midzone segments of W64A(T) was blocked by a toxin concentration which did not affect augmentation development in W64A(N). Augmentation development was more toxin-sensitive in T than in N cytoplasmic versions of all inbreds tested. Fertility-restoring nuclear loci decreased but did not eliminate the toxin sensitivity of augmentation developments as observed in root midzones of inbred A619(T). Chloramphenicol-and/or cycloheximide-sensitive protein synthesis was required for augmentation development, but not for expression of either basal or augmented K(+) uptake.