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DOI: 10.1055/s-2006-946675
© Georg Thieme Verlag KG Stuttgart · New York
Frequency and Timing of Leaf Removal Affect Growth and Podophyllotoxin Content of Podophyllum peltatum in Full Sun
Publication History
Received: October 21, 2005
Accepted: May 6, 2006
Publication Date:
22 June 2006 (online)

Abstract
Podophyllotoxin is a pharmaceutical compound found in leaves and rhizomes of American mayapple (P. peltatum L.), a species being investigated as an alternative to that of the Indian mayapple (P. emodi). Leaves alone can serve as a renewable source of podophyllotoxin (and other lignans) leaving rhizomes undisturbed to produce leaf biomass in subsequent years. It is not known, however, how frequently or severely plants can be defoliated without adversely affecting future plant growth, lignan content, or podophyllotoxin yield (g·m-2). This study compared harvest strategies that were mild to severe in frequency and timing of leaf removal. A wild population in full sun was subjected to leaf removal treatments of varying frequency (every year, every 2nd or 3rd year) and timing (early or late). Control plots not previously harvested were included every year. Plots were 1.0 m2 and established during spring of 2001. Duration of the study was four years. P. peltatum plants did not tolerate the most severe harvest treatment: annual harvest frequency in combination with early harvest time. Early annual harvests reduced total leaf dry mass and total leaf area in a consistent and linear manner. In contrast, plants tolerated annual harvests when conducted late in the growing season and tolerated early harvests when conducted every 2nd or 3rd year. The number of sexual shoots was reduced to zero by early annual harvests. Podophyllotoxin content was 2.7 to 6.5 times greater in leaves harvested early compared to those harvested late, though content was significantly greater in only two out of four years. In conclusion, we can recommend leaf removal every year from well-established P. peltatum populations grown in full sun if harvests are conducted late in the growing season. This harvest strategy ensures maximum podophyllotoxin yield without jeopardizing future leaf biomass yield. Leaves harvested early appear to have greater podophyllotoxin content, but we discourage early harvest every year. Instead, our results indicate that leaves can be harvested early every other year without reducing long-term performance of P. peltatum populations.
Key words
American mayapple - lignans - α-peltatin - β-peltatin - defoliation
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Dr. Kent Cushman
Southwest Florida Research & Education Center
University of Florida
Institute of Food and Agricultural Sciences
Immokalee
FL 34142
USA
Phone: +1-239-658-3429
Fax: +1-239-658-3469
Email: kcushman@ufl.edu
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