AbstractPhosphatase inhibitors were applied to immature sugarcane through the foliage and roots to determine whether such materials would suppress phosphatases in living tissues, and whether the induced inhibition would be accompanied by increased sucrose content. Molybdenum, at rates of 2, 20, and 200 p.p.m., and F at rates of 1, 10, 100 p.p.m. were applied as foliar sprays to 14-week-old plants grown' by sand culture in the greenhouse. Leaf samples were taken for sugar and enzyme analyses at 0, 3, 9, 18, and 27 days following treatment. A second group of plants, likewise grown in sand culture, was supplied with Mo as a nutrient variable at rates of 0, 0.01, and 1.0 p.p.m. elemental Mo, and with Ca at concentrations of 1.0, 3.0, and 9.0 meq./liter. It was believed that Ca should enhance any inhibitor effects induced by Mo. One harvest was taken for sugar and enzyme analyses when the plants were 9 weeks of age. A large number of significant sugar and enzyme variations was induced by the variable Mo and F treatments. Phosphatase inhibition was usually accompanied by increased sucrose, although these effects were usually not consistent among all harvests. The most consistent response was obtained with 20 p.p.m. of Mo. This treatment suppressed phosphatases, particularly ATP-ase and glucose-1-phosphatase, and was still accompanied by a higher sucrose content after 27 days. The effects of F were more sporadic. Significant results were recorded from 10 p.p.m. at 18 days and from 100 p.p.m. at 27 days, with phosphatase suppression and increased sucrose appearing concurrently. It was found that when Mo was supplied as a nutrient variable in factorial combination with Ca, the high level of Mo (1.0 p.p.m.) suppressed phosphatase and was accompanied by an increase of sucrose, but only so long as Ca was supplied at a low level (1.0 meq./liter). Calcium at 3.0 and 9.0 meq./liter retarded or completely eliminated the ability of Mo to suppress phosphatases. The importance that a Ca X Mo interaction may play in areas where liming is considered beneficial for sugarcane is discussed. Molybdenum at a medium level (0.01 p.p.m.) was found to act as an activator of the acid phosphatases. This agrees with earlier observations recorded by the author while studying the Mo nutrition of cauliflower. The results appear to verify the hypothesis that phosphatase inhibitors can be supplied to living tissues without damage to the plants, that phosphatases will be suppressed below normal activity levels, and that the suppression will be accompanied by increased sucrose. The increase of sucrose is apparently a result of a more favorable supply of ATP and phosphorylated hexoses needed for the biosynthesis of sucrose.
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