| Naphthalene is a representative of polycyclic aromatic hydrocarbons(PAHs),existing widely in the atmosphere,soil and water.Naphthalene is one of the pollutants monitored priority by EPA in USA,as well as one of 58 toxic organic pollutants controlled priority in China".PAHs are combined with the solid particles and aerosol in the air,then into soil and water through the dry and/or wet sedimentation.Some studied have shown that most water systems have been polluted by polycyclic aromatic hydrocarbons(PAHs),and the contents of polycyclic aromatic hydrocarbons(PAHs) in some rivers have been seriously beyond safe level.In this paper,researched were focused on the capacities of plants to enrich naphthalene in water and to restore healthy wate.Seven plant species were chose -- canna(Canna generalis),ryegrass(Lolium multiflorum Lam),reed(Phragmited communis),cattail(Typha latifolid),Scirpus yagara(Scirpus tabernaemontani Gmel),Scirpus tabernaemontani(Scirpus yagara Ohwi),Jade cicada flower(Iris ensata Thunb).Seedlings of these seven plants were transplanted into solutions with 10 mg/L,20 mg/L,40 mg/L,80 mg/L naphthalene, respectively.Seedlings growing in solution without naphthalene were regarded as control treatmen.Several plant morphological traits and physiological and biochemical indexes, which were measured at different naphthalene concentration solutions,were used to compare the capacities on naphthalene enrichment and restore effect among seven plant species. Meanwhile,the migration of naphthalene in plants and resistance mechanisms were discussed.The results shown as below:(1) In the 0-40 mg/L concentration,the appearance of seven plant species were normal, In the 80 mg/L concentration,the greatest injury was appeared in canna and Jade cicada flower indicating the naphthalene pollution had a stronger inhibitory effect on sprout length of the two plant species.Plant biomass were promoted in low concentrations of naphthalene solution but inhibited in high concentrations.The influences of naphthalene on the growth of Scirpus yagara were not distinct.(2) Photosynthetic rate,transpiration rate and chlorophyll content of the plants basically followed the same trend under the naphthalene stress,but the reduction of chlorophyll content was less than the reduction of photosynthetic rate.The effect of naphthalene on photosynthesis and respiration rate of Jade cicada flower was remarkable.POD activity and MDA content increased with lower naphthalene stresses,then decreased with higher naphthalene stresses.POD activity and MDA content of ryegrass were the greatest at the 10 mg/L concentration,and canna,Scirpus yagara,Scirpus tabernaemontani,Jade cicada flower were greatest in the 20 mg/L concentration,the reed and cattail in the 40 mg/L concentration.(3) With the increasing concentration of naphthalene,the enrichment amounts in plant increased too.At the concentration of 10mg/L,the largest amount of naphthalene enriched was 3.853μg/g in cattail,4.670μg/g in ryegrass at 20 mg/L concentration,5.130μg/g in ryegrass at 40 mg/L,and 5.273μg/g in reeds at 80 mg/L,respectively.The amount of naphthalene remained in water increased with the naphthalene concentration.The smallest amount of naphthalene remained in each concentration occurred with cattail,cattail,ryegrass, reed,respectively,consisting with the enrichment amount.In addition,the size of plant leave and density may affect the naphthalene volatilization,and the naphthalene in plant were in different degree of degradation,all of these may affect the plant enrichment amount and the remaining amount in water.(4) In this experiment,the distribution of naphthalene in plant organs were similar among seven species,with largest amount in the roots,medium in leaves,lowest in stems, indicating the adsorption of naphthalene from the root to the leaves through the stems. Different plants showed different transporting capacity as the concentration of naphthalene increasing.
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