Sucrose-Enzyme Relationships in Immature Sugarcane Treated With Variable Molybdenum, Calcium, Iron, Boron, Lead, Trichloroacetic Acid, Beta-glycerophosphate, and Starch

Abstract

Variable levels of the elements molybdenum, calcium, iron, lead, and boron, as well as trichloroacetic acid, ß-glycerophosphate, and starch, were supplied to immature sugarcane grown in the greenhouse. Molybdenum, calcium, and iron were provided in factorial combination to plants in sand culture. Molybdenum, lead, and starch were applied as foliar sprays to a second group of plants grown in soil, and boron, ß-glycerophosphate, plus trichloroacetic acid were likewise applied to the foliage of plants grown in soil. The objectives of these experiments were to determine whether any of the applied materials could alter the action of specific enzymes, and, if so, whether significantly greater sucrose content would result. Leaf and meristem tissues were assayed for sugars, and for the enzymes amylase, invertase, acid phosphatases, starch phosphorylase, peroxidase, and polyphenol oxidase. Molybdenum significantly increased sucrose when applied as a foliar spray (80 p.p.m.), and as a nutrient in sand culture (1 p.p.m.). The molybdenum effect was retarded or reversed when either high calcium (9 p.p.m.) or high iron (6 p.p.m.) was supplied concurrently. Acid phosphatases and amylase were suppressed by high molybdenum, although these effects were greatly dependent upon calcium and iron supply. When applied as a foliar spray, molybdenum suppressed amylase and the phosphatase hydrolyzing glucose-1-phosphate, but not ATP-ase or ß-glycerophosphatase. Invertase was suppressed by high iron (6 p.p.m.) when molybdenum and calcium were low, but was stimulated when molybdenum was high. Lead, when applied to leaves at the rate of 50 p.p.m., caused moderate sucrose increases. Glucose-1-phosphate phosphatase was suppressed by lead in leaves and meristem, as was starch phosphorylase in the leaves. Foliar starch application failed to stimulate amylase, while ß-glycerophosphate failed to inhibit starch phosphorylase or to induce greater phosphatase activity. A number of enzyme responses were obtained which do not happen in vitro, and known in vitro effects did not always appear when specific materials were applied to living plants. Trichloroacetic acid, in particular, appeared to stimulate rather than inhibit enzyme action in vivo. This and other consequences of applying enzyme-regulating materials are discussed in detail.