Effects of long light exposure and drought stress on plant growth and glucosinolate production in pak choi (Brassica rapa subsp. chinensis).

Glucosinolates (GLs), found in Brassicaceae family, are precursor metabolites with anti-cancer properties. Increased GLs have been studied under various environmental growth conditions. Pak choi (Brassica rapa subsp. chinensis) is a GL-rich vegetable. We hypothesize that long exposure to light and drought will increase the biomass of, and GL production in, pak choi. The experiment was conducted for 6 weeks. Long light exposure (20 h/day) increased, whilst drought exposure (12 h/week) decreased the plant growth. The plants exposed to a combination of drought and long light conditions showed similar growth pattern as control plants. GL production increased at week 6 in plants exposed to long light, while drought exposure had no impact on GL production, with the exception of glucoraphanin. Significant positive correlations were observed between plant growth and GL yield with accumulated light exposure time. Our findings suggest that long exposure to light can be used to increase both the biomass and GL production in pak choi.