Morphological and Biochemical Changes in Ginseng Seedling Roots Affected with Stripe Symptoms

Abstract

A unique symptom of longitudinal red stripes on the surface of one-year-old ginseng roots was studied to determine the morphological and biochemical changes taking place. Light and scanning electron microscopy, measurements of phenolic and mineral element content, and enzyme activity, were compared between healthy and stripe-affected root tissues. Light microscopy revealed that the root epidermis had ruptured and fissures extended for 3 - 4 cell layers into the cortex. Phenolic compounds accumulated in the epidermal cells which stained with Toluidine blue 0. Total phenolic content was higher in tissues from striped roots compared to healthy roots and HPLC profiles showed increases in a number of specific phenolic compounds. Analysis of epidermal tissues by SEM-EDX for mineral element content showed a marked increase in levels of iron, silicon and aluminum and a decline in potassium in striped root tissues. The activity of the enzymes phenylalanine ammonia lyase and peroxidase were also found to be higher in striped root tissues. Striping of ginseng roots is a physiological condition caused by a rupture of the epidermis due to rapid growth of underlying cells, which results in phenolic accumulation and sequestration of several minerals. Further oxidation causes a visible red striping on the root surface.