Camptothecin production in Camptotheca acuminata seedlings in response to shading and flooding

Abstract

One-year-old Camptotheca acuminata seedlings were grown under heavy shade (27% full sunlight), slight shade (67% full sunlight), or full sunlight for 2 weeks, then subjected to flooding for 4 weeks under continued shading schemes. Growth, chlorophyll fluorescence, and camptothecin concentrations were determined. Flooding led to significant decreases 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 significantly higher chlorophyll fluorescence than the non-shaded leaves throughout the 6-week period. Onset of flooding caused immediate decline of chlorophyll fluorescence of nonshaded and slight-shaded seedlings, but the effect of flooding quickly diminished. Heavy shade led to elevated camptothecin concentrations in leaves, whereas flooding had no effect. Camptothecin concentrations in stems were not altered by either flooding or shading; however, they were substantially lowered in lateral roots under heavy shade compared with those grown in full sunlight. Flooding induced an additional camptothecin accumulation in lateral roots under slight shade, but it failed to do so under either heavy shade or full sunlight conditions. Key words: anti-tumor compounds, camptothecin, chlorophyll fluorescence, flooding, secondary metabolites, shading.