Factors affecting podophyllotoxin yield in the ex situ grown Podophyllum hexandrum, an endangered alpine native of the western Himalayas.

This study reports an appreciable yield of podophyllotoxin (PDT) in P. hexandrum plants grown ex situ under polyhouse conditions of a temperate locale. The PDT content of below-ground parts was affected by both plant age and growth period. However, only the effect of plant age on PDT content was significant. Thus, the highest amounts of PDT were recorded in the below-ground parts of 2-year-old plants harvested during the late-growth period (LGP). High total soluble sugars in the below-ground parts during the early growth period (EGP) and the highest nitrate and nitrate reductase in the leaves of 2-year-old plants during the peak-growth period (PGP) indicated higher mobilization and assimilation of starch and nitrate. Probably the surplus carbon and nitrogen gained during the PGP were diverted from aerial parts to below-ground parts during the LGP and in turn contributed to the synthesis of higher amounts of PDT. This study shows that commercial cultivation of P. hexandrum is possible under ex situ temperate conditions.