Effects of chronic exposure to microcystin-LR on phosphorus uptake and accumulation of <i>Acorus calamus.</i>

To investigate the effects of chronic exposure to microcystin-LR (MC-LR) on phosphorus (P) uptake and accumulation in <i>Acorus calamus</i>, we examined the growth status, root vigor, malondialdehyde (MDA) content, type 2C serine/threonine protein phosphatase (PP2C) activity, as well as changes in phosphorus uptake characte-ristics and phosphorus accumulation in <i>A. calamus</i> under MC-LR concentrations of 0 (control), 1, 10, and 30 μg·L^-1 in a hydroponic system for 25 days. The results showed that after exposure to 1 μg·L^-1 MC-LR, root biomass of <i>A. calamus</i> increased by 12.1%, root vigor enhanced by 33.6%, and the plant's affinity and uptake potential for phosphorus increased, thereby promoting phosphorus uptake and accumulation. After exposure to 10 μg·L^-1 MC-LR, root vigor and MDA content of <i>A. calamus</i> showed no significant change, while root PP2C activity decreased by 25.4%, with negative impact on phosphorus uptake and accumulation. After exposure to 30 μg·L^-1 MC-LR, root vigor of <i>A. calamus</i> decreased by 25.8%, MDA content increased by 48.9%, PP2C activity reduced by 48.5%, root biomass decreased by 11.2%, and the plant's affinity and uptake potential for phosphorus decreased, inhibiting phosphorus uptake and accumulation. However, phosphorus preferentially transferred to the aboveground part to meet the demand of stems and leaves for phosphorus. Our results indicated that chronic exposure to higher concentrations (≥10 μg·L^-1) of MC-LR had varying degrees of inhibitory effects on phosphorus uptake and accumulation in <i>A. calamus</i>, which would adversely affect its growth.