| Heavy metal pollutants in water have high stability and hard degradation,It can realize ecological restoration by using heavy metal hyperaccumulator to absorb,enrich and store heavy metals.In the paper,the seed germination,the morphological structure response and the tolerance,enrichment,distribution,and transport of Typha orientalis Presl.to lead and the migration dynamics of lead ions in root were studied by using hydroponics,scanning electron microscope,microwave digestion method and the energy X-ray spectroscopy.The results were as follows:1.Different concentrations of Pb2+ inhibited seed germination and seedling growth of Typha orientalis Presl.,and the inhibition increased with increasing concentrations.When the concentration of Pb2+ were 0.25,1,and 3 mmol·L-1,the germination rates and germination energy of the seeds were significantly decreased by 22.18%,48.64%,89.88%and 22.45%,46.94%,89.39%,respectively.The germination indexes and vigor indexes were also significantly decreased by 17.56%,43.12%,86.98%and 51.56%,97.93%,99.73%.The elongation of radicles and the growth of primary leaves were negatively correlated with the concentrations of Pb2+ treatment,and the inhibition effect of radicles elongation were more obvious.When the concentration of Pb2+ was more than 0.25 mmol·L-1,the inhibition indexes of radicles and primary leaves decreased by more than 50%compared with the control.When Pb2+ concentration was 3 mmol·L-1,the radicles and primary leaves stopped growing.It indicated that 0.25 mmol·L-1 was the sensitive concentration of Pb2+ influence on seed germination,3 mmol·L-1 was the maximum lethal concentration.2.The results of response to different concentrations of Pb2+ stress to the roots and leaves of Typha orientalis Presl.showed that when the Pb2+ concentration was greater than 0.9 mmol·L-1,the lateral roots had stopped growing,the root epidermis shrank,the cortical cells became loosely arranged,and some cortical cells disintegrated after treatment for 10 days.After treated with Pb2+ at a concentration of 0.9 mmol·L-1 or more,the epidermal cells became denser,the stomatal density increased,and mechanical tissues were evacuated.When the Pb2+concentration was lower than 0.9 mmol·L-1,the plants showed tolerance to Pb2+ stress.3.Under different Pb2+ concentrations treated after 10 days,the effects of different seedling ages on heavy metal lead enrichment,distribution,and transport were as follows:(1)When the Pb2+ concentration was greater than 0.9 mmol·L-1,the fresh weight,plant height,and leaf width were significantly lower than those of the control,but dry weight and root length were not significantly affected by Pb2+ concentration.The younger the seedling ages,the higher Pb2+ stress concentrations and the longer the stress time,the more severe the poisoning symptoms;(2)The tolerance indexes for Pb2+ of different seedling ages were 0.711?0.942(all>0.6),and the tolerance limits were 24.195?37.056 mg·g-1 FW,indicated that Typha orientalis Presl.had high tolerance to Pb2+;(3)The contents of Pb2+ in the roots and leaves were positively correlated with the treatment concentrations.The distribution factor(DF)of Pb2+ in the tissues showed that DFroots>DFleaves.The absorbed Pb2+ mainly accumulated in roots(>92.5%);(4)Pb2+ were more easily enriched when treated with low concentration of 0.3 mmol·L-1,and the bioconcentration factors were up to 6.09?9.018.The average bioconcentration factors of Pb2+ from different seedling ages were 3.70?6.26,but the translocation factors were 0.033?0.305.It indicated that the different seedling ages of Typha orientalis Presl.had strong Pb2+ enrichment ability,but their transport capacities were low.4.Under the Pb2+ concentration of 0.9 mmol·L-1 and room temperature of 25?,the linear distance of Pb2+ from the root epidermis to the center of the pith was 496 ? m,which lasted for 15 s.Spectroscopic examination showed that Pb2+ migrated from the epidermis to the cortex,from the cortex to the vascular tissue,and to the central part of the pith for approximately 5 s.It was calculated that the migration rate equations were as follows:y =68.462x + 4.9697,y = 51.482x + 317.04,y = 32.195x + 431.81,and the lateral migration rate of Pb2+ in the root was 0.228 m·h-1.The longitudinal migration distance of Pb2+ in the root catheter was 1 cm,which lasted for 135 s,the longitudinal transport rate was 0.267 m·h-1. |
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