Podophyllotoxin Content and Yield of American Mayapple Leaves in Sun and Shade

Abstract

Four levels of shade (0%, 30%, 55%, and 80%) were used to determine their effect on growth and lignan content of american mayapple (Podophyllum peltatum L.). Mayapple rhizomes were harvested from the wild and transplanted into plant beds on 20 Dec. 2001 using a randomized complete block design with four blocks. Growth and lignan content were recorded during spring of 2002 and 2003. Leaf samples were analyzed for the following lignans: podophyllotoxin, alpha-peltatin, and beta-peltatin. Increasing levels of shade increased shoot longevity, leaf area per plant (cm2/plant), and shoot height. Shade did not affect shoot emergence, total leaf area (cm2·m-2), or leaf dry mass (g·m-2 or g/plant). Regardless of year, podophyllotoxin and total lignan contents at 0% shade were significantly greater than those at 80% shade, and the overall trend was for decreasing contents with increasing shade. Shade did not affect alpha-peltatin content. Content of beta-peltatin was greatest at 0% shade compared to the other three shade treatments. Year affected alpha-peltatin and beta-peltatin contents, with less content of each in 2003 than in 2002. There were large numerical decreases in podophyllotoxin yield (podophyllotoxin content per unit area, mg·m-2) as shade increased from 0% to 80%, but these differences were only marginally significant (P = 0.0897). In contrast, podophyllotoxin yield was significantly greater in 2003 than in 2002 as total leaf area and dry mass significantly increased. Increasing levels of shade slightly decreased air and soil temperatures. Our results indicate that american mayapple is not a shade-requiring species. Under full sun (0% shade) shoots did not persist as long as under shade and leaves were smaller and thicker, but total lignan content was significantly greater than under shade. It appears that growers of specialty crops serving the pharmaceutical industry can establish and cultivate american mayapple under full sun, thus providing leaf biomass with high podophyllotoxin content while avoiding the cost of expensive shade structures.