Dimethyl phthalate (DMP) is one of the most
widely used plasticizers. Due to its anthropogenic inputs,
DMP has become a serious contaminant in soils and water.
Hydroponic experiments were conducted focusing on
phytotoxic responses of rice seedlings ( Oryza sativa
XZX 45) to 1,2-dimethyl phthalate. Relative growth rate
(RGR) and water use efficiency (WUE) were measured as
response endpoints to quantify the effective concentrations
(ECs) of DMP to rice seedlings. As a comparison, acute
phytotoxicity of dimethyl sulfoxide (DMSO) used as solvent
media was also determined. Results showed that acute
toxicity of DMP to rice seedlings was evident, but selected
endpoints had different responses to DMP exposure. RGR
of rice seedlings was more sensitive to change of DMP
than WUE. EC-48 h values for 10, 20 and 50 % inhibition
of the RGR were estimated to be 6.18, 38.41 and
329.41 µM for rice seedlings exposed to DMP, respectively,
while smaller ECs were obtained for 96 h exposure.
Results from phytotoxicity of DMSO demonstrated that the
doses of DMSO used for dissolving DMP had a negligible
effect on rice seedlings. In conclusion, DMP is problematic
at relatively low concentrations for rice seedlings, and
inhibitory effects are highly dependent on response endpoints
and the duration of exposure period.