Evaluation of Sucrose-Enzyme Relationships among 12 Puerto Rico Sugarcane Varieties

Abstract

Sugar-enzyme relationships were evaluated among 12 Puerto Rico sugarcane varieties. There were two objectives: 1, To discover enzyme-activity trends which would help account for characteristic variety properties; and 2, to seek enzyme-activity trends which indicate at an early age the sugar-producing capacity of new or test varieties. All plants were grown in sand culture with controlled nutrient supply. Leaf and meristem samples were frozen at 10 weeks for sugar and enzyme assay. Sugar and enzyme values varied greatly among the 12 varieties, although at harvest all varieties appeared quite similar as to size and vigor. Fructose and sucrose content differed by as much as tenfold among variety extremes. Amylase, invertase, tyrosinase, and peroxidase all exhibited broad differences. Three variety characteristics were correlated with enzyme action, including cane tonnage, percent-sugar in cane, and sugar per acre. Leaf amylase appeared to affect both cane tonnage and percent-sugar in cane. Leaf phosphatase was particularly active in varieties rated as "low" sugar producers. In meristem, both invertase and peroxidase showed direct correlations with cane tonnage, with activity increasing from low to high as tonnage potential increased. High invertase also correlated with "low" percent-sucrose, and with "low" sugar per acre. Both meristem tyrosinase and peroxidase were excessively active among varieties rated as "low" sugar producers. Since meristematic enzymes can be assayed at a very early age, it was suggested that invertase be employed as an early indicator of sugar-producing potential with test varieties. Peroxidase and amylase also show promise in this respect.