Germinating and Culturing Axenic Poison Ivy Seedlings

Abstract

Urushiols are the chemical constituents responsible for causing the characteristic skin rash resulting from contact with poison ivy [Toxicodendron radicans subsp. radicans (L.) Kuntze] plant tissue. Future detailed physiological and molecular studies of T. radicans urushiol metabolism will require the production and cultivation of axenic T. radicans plants in controlled environments. To this end, the present study focused on treatments to enhance germination and reduce microbial contamination to obtain axenic T. radicans seedlings. Toxicodendron radicans drupes treated singularly with water, bleach, cold, or gibberellic acid showed very low germination frequencies. In contrast, concentrated sulfuric acid strongly promoted seedling germination by removing exocarp, mesocarp, and causing pitting of the brachysclereid and osteosclereid layers of the endocarp. Most T. radicans drupes harbored significant amounts of fungal and bacterial contaminants. Although the serial mechanical scarification, sulfuric acid, and bleach treatments promoted seedling germination, this serial treatment regime was not adequate to render the majority of drupes microbe-free. Nevertheless, ≈25% of treated T. radicans drupes were axenic, and these needed to be promptly separated from adjacent fungal-contaminated drupes to avoid cross-contamination. The isolated axenic T. radicans drupes germinated at high frequency producing viable seedlings that grew well in sterile plant culture conditions.