Influence of Variable Manganese and Silicon on the Nutrition, Sugar Production, and Enzyme Activity of Immature Sugarcane

Abstract

Sugarcane variety M. 336 was grown in solution culture for 3 months under 3 Mn levels (0, 10, and 100 p.p.m.) and 3 Si levels (0, 50, and 500 p.p.m.) to study the influence of various levels of Mn and Si on growth, nutrient composition, and enzyme and sugar activity. The uptake of Mn by the immature sugarcane plant was definitely suppressed by increasing Si levels in the nutrient medium. As the Mn content of the plant dropped Si content increased. However, the converse did not hold, for when the cane plant was faced with an excessive supply of Mn, it attempted to compensate by increasing its Si uptake. High-Si X high-Mn treatment severely stunted growth, but yielded the maximum sucrose values recorded. Leaf-protein content was highest with all plants at the high Si level, but meristem protein reflected a reverse response. The greatly retarded growth caused by high Si and high Mn was accompanied by marked suppression of both starch phosphorylase and the phosphatases. Polyphenol oxidase showed a greater sensitivity to variable Mn and Si than any other enzyme assayed. Possible roles of Mn and Si in the mechanisms of auxin and protein synthesis are discussed.