Effect of th brown midrib-three gene on corn grain utilization by growing rats.

A study was conducted to determine the effect of the brown midrib-three (bm3) gene for low lignin in corn plants on grain utilization by growing rats. No differences in total body weight gain were observed between rats fed bm3, normal and iso-N bm3 (isonitrogenous to normal) grain diets with or without supplemental dietary protein. Body weight gains for rats fed bm3, normal and iso-N bm3 grain diets were 39.6, 35.2 and 31.6 g, respectively, when no supplemental protein was fed, and 134.6, 142.1 and 132.2 g when supplemental protein as soy protein was fed to increase crude protein to 11 to 12%. No differences in feed conversion were observed between rats fed bm3, normal and iso-N bm3 grain diets at either level of dietary protein. Feed to gain ratios were 8.7, 9.4 and 10.7 when no supplemental protein was fed and 3.2, 3.2 and 3.4 when supplemental protein was fed. According to this study, this bm3 gene has no effect on grain utilization by the growing rat.

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.

Influence of Helminthosporium maydis, Race T, Toxin on Potassium Uptake in Maize Roots.

The effect of a toxin extract of Helminthosporium maydis, race T on K(+) ((86)Rb) uptake by excised root segments of normal (N) and Texas cytoplasmic male-sterile (T) versions of corn inbred W64A was investigated. The uptake of K(+) was inhibited in both N and T roots by the toxin. This was true for both basal (freshly excised) and augmented (pretreated with aeration) K(+) uptake. Augmented uptake was more toxin-sensitive than basal uptake (irrespective of cytoplasm type), and the augmented uptake in T roots was seven to eight times more toxin-sensitive than in N roots.Specific zones of roots differed in their basal and augmented K(+) uptake rates as well as their toxin sensitivities. The root apex of T was more sensitive to toxin than the apex of N roots when basal K(+) uptake was measured. In mature zones of the root, T was more sensitive than N when augmented rates were measured. During the development of the augmented K(+) uptake capacity in either N or T roots, the sensitivity to the toxin did not change; uptake in N roots was inhibited by 10 to 25% and uptake in T roots was inhibited by 70 to 80%.The difference in toxin sensitivity of K(+) uptake between N and T roots may be due to N possessing a protective mechanism which is deficient in T.