Light Intensity Affects Growth, Photosynthetic Capability, and Total Flavonoid Accumulation of Anoectochilus Plants

Anoectochilus formosanus, a medicinal plant used to treat hypertension, lung disease, and liver disease, was grown to maximize biomass and secondary metabolite production in a controlled environment under four levels of photosynthetic photon flux (PPF), namely, 10, 30, 60, or 90 mu mol.m(-2).s(-1), that is L-10, L-30, L-60, and L-90 treatments, respectively. On Day 45, all growth values were greatest for the L-30 plants. Dry weight was lowest for the L-10 plants. Leaf area, stem length, and fresh weight were lowest for the L-90 plants. The chlorophyll concentration was highest in the L-10 treatment and decreased with increasing PPF. Electron transport ratios of leaves were highest in the L-30 treatment and lowest in the L-90 for the second leaf (counted down from the apex) and in the L-10 for the third leaf. An increase in light intensity from 10 to 60 mu mol.m(-2).s(-1) increased the superoxide dismutase activity and was associated with an increase in the total flavonoid concentration. The total flavonoid concentration (mg.g(-1) DW) was greatest in the L-60 and lowest in the L-90. However, the total flavonoid content (mg/plant) was highest in the L-30 plants as a result of great biomass. The results indicated that A. formosanus is a typical shade plant suitable to grow under low light intensity at PPF of 30 to 50 mu mol.m(-2).s(-1) for both growth and production of total flavonoid. A light intensity of 90 mu mol.m(-2).s(-1) induced stress on plant growth and reduced photosynthetic capability and the flavonoid accumulation.