关键词: 净化效果, 植物生长, 潜水式生态介质箱, 黑臭水体, 生态浮床

Abstract: To study the effects of nitrogen (N) nutrition on the growth and active components of Isatis indigoticaFort., five N levels (0, 2.5, 5, 10, 15 mmol·L^-1, designated as N0, N1, N2, N3, N4 respectively) were applied in a pot experiment in greenhouse. The growth characteristics, photosynthesis parameters, N assimilation contents, N metabolism enzyme activities, the contents of indigo, indirubin, and total flavonoid in leaves and epigoitrin content in roots were measured. The results showed that plant height, main root diameter, and dry biomass of I. indigotica seedlings significantly decreased and rootshoot ratio increased under N0-N3 treatments. With the decreases of N level, the chlorophyll content, carotenoid content, net photosynthetic rate, transpiration rate and stomatal conductance of leaves gradually decreased, while the intercellular carbon dioxide concentration increased. The contents of soluble protein, free amino acid, and nitric N in leaves were decreased, and nitrate reductase activity and glutamine synthase activity were inhibited under low N nutrition. The contents of indirubin and total flavonoid in leaves under N0-N2 treatments were at higher levels. In contrast, contents of indigo in leaves were decreased significantly under low N nutrition and epigoitrin contents in roots were the lowest at N0 treatment. In conclusion, the growth and partial physiological characteristics of I. indigotica seedlings were significantly influenced by low N levels. The contents of indigo in leaves and epigoitrin contents in roots were declined under low N levels, while the accumulations of indigo and total flavonoid were promoted. Considering the biomass and active component contents, the yield and active components will show good performance under the N application levels of 10-15 mmol·L^-1.

Key words: black and odorous water body, purifying effect, submerged group ecological media box, growth status of plant, ecological floating bed