Exocellular Enzymes of Corn Roots

Abstract

Little attention has been given to the occurrence of exocellular hydrolytic enzymes associated with the roots of higher plants. Such enzymes, if present, could solubilize macromolecular constituents of organic soils, permitting uptake and utilization by the plant of the resultant low molecular weight organic compounds. The present work supports this concept by demonstrating that several exocellular hydrolytic enzymes are associated with the roots of intact corn seedlings. Distinction has been made between exocellular enzymes released into the culture media and enzymes apparently bound to the root surface. A previous paper from this laboratory (17) reviewed earlier studies and presented evidence for the occurrence of exocellular enzymes associated with the primary cell wall of corn coleoptiles. Of particular relevance to the present work is a report (36) of the secretion of peroxidase, acid phosphatase, indolylacetic acid oxidase, and amylase into the culture media bathing plant *tissue cultures. In addition, reports have appeared (2, 6, 14) of the occurrence of an exocellular invertase, possibly involved in sucrose metabolism by roots. In the present work it is reported that invertase, cellobiase, adenosine triphosphatase, pyrophosphatase, and nuclease activity is observed when appropriate substrates are added to nutrient solution bathing the roots of intact seedling corn plants. In addition, inveritase and nuclease are detected as soluble enzymes in the nutrient solution.