AbstractVariable concentrations of tungsten and molybdenum were applied as foliar sprays to 12-week-old sugarcane grown in sand culture. The objectives were to evaluate both elements as in vivo inhibitors of amylase, invertase, and acid phosphatases, and to test further the hypothesis that such inhibition will result in increased sucrose content. Leaf and meristem samples were harvested just prior to initial treatment, and at 3, 9, and 27 days thereafter. Glucose-1-phosphatase and amylase were generally inhibited by both elements, and increased sucrose usually appeared as a consequence. Tungsten at 10 p.p.m. significantly increased sucrose in leaf and meristem at all posttreatment harvests. Molybdenum was a more effective phosphatase inhibitor than tungsten, but was less effective in promoting sucrose production. Molybdenum increased sucrose in meristem only. ß-glycerophosphatase and ATP-ase were stimulated by some of the treatments. This was totally unexpected since both enzymes are known to be inhibited by tungsten and molybdenum in vitro. Certain treatments appeared to reduce the enzymes' capacity to experience major fluctuations. The significance of this property and the stimulation of ATP-ase are discussed at length.
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