Responses of Artemisia annua L. to lead and salt-induced oxidative stress

The Artemisia annua L. plants were subjected separately to NaCl (0-160 mM) and lead acetate (0-500 μM) at the age of 90 days (S1 treatment) and 120 days (S2 treatment). The treated plants were studied on 100, 130 and 160 days after sowing (DAS) in S1, and on 130 and 160 DAS in S2 treatments for lipid peroxidation rate, photosynthetic rate (Pn), chlorophyll content, artemisinin concentration and artemisinin yield in leaf samples and for total biomass accumulation. The treatments enhanced lipid peroxidation at all stages of plant growth and increased the concentration and yield of artemisinin at 100 and 130 DAS in S1 and S2, respectively, while other parameters declined at all growth stages. The magnitude of changes was greater in lead-treated than in salt-treated plants. Both treatments induced oxidative stress which might have damaged the photosynthetic apparatus resulting in a loss of chlorophyll content and a decline in photosynthetic rate, biomass accumulation and artemisinin production. The increase in artemisinin content, observed during the early phase of plant growth, might be due to a sudden conversion of its precursors (e.g. artemisinic acid/dihydroartemisinic acid) to artemisinin by activated oxygen species under oxidative stress.