CAMPTOTHECIN PRODUCTION IN CAMPTOTHECA-ACUMINATA SEEDLINGS IN RESPONSE TO SHADING AND FLOODING

One-year-old Camptotheca acuminata seedlings were grown under heavy sh ade (27% full sunlight), slight shade (67% full sunlight), or full sun light for 2 weeks, then subjected to flooding for 4 weeks under contin ued shading schemes. Growth, chlorophyll fluorescence, and camptotheci n concentrations were determined. Flooding led to significant decrease s in leaf biomass, while shading significantly increased stem biomass. Under full sunlight or slight shade conditions, lateral root biomass was significantly decreased by flooding, whereas under heavy shade, it was not significantly reduced by flooding. Shaded leaves displayed si gnificantly higher chlorophyll fluorescence than the non-shaded leaves throughout the 6-week period. Onset of flooding caused immediate decl ine of chlorophyll fluorescence of nonshaded and slight-shaded seedlin gs, but the effect of flooding quickly diminished. Heavy shade led to elevated camptothecin concentrations in leaves, whereas flooding had n o effect. Camptothecin concentrations in stems were not altered by eit her flooding or shading; however, they were substantially lowered in l ateral roots under heavy shade compared with those grown in full sunli ght. Flooding induced an additional camptothecin accumulation in later al roots under slight shade, but it failed to do so under either heavy shade or full sunlight conditions.