Abstract: A hydroponic experiment was conducted to study the growth responses of Phytolacca americana to the stress of different Mn concentrations (1, 5, 8, 12, and 15 mmol·L^-1). With the increasing Mn concentration in growth medium, the seed germination rate, germination potential, and mitotic index of P. americana decreased, root growth was inhibited gradually, root activity presented a decreasing trend, and the biomass of plant organs reduced. Under the stress of Mn≥ 12 mmol·L^-1, the Mn had very obvious toxic effect on the growth of P. americana, which was manifested in the serious inhibition of seed germination, root tip’s cell division, and seedling’s root growth and in the significant decrease of plant biomass. Mn stress had little effects on the buds of P. americana seedlings, but large effects on the reproductive organ, resulting in a great decrease of bearing fruit quantity and quality.

Key words: Nutrient, Nutrient limitation, Yellow Sea, East China Sea, Changjiang River estuary