Studied On The Photosynthetic Characteristics Of Halogeton Glomeratus In Jinchuan Mining Area Under Heavy Metal Stress

The heavy metal pollution which generated in the mining process poses a great threat to the local ecological environment,and the destruction of land resources and landscape cannot be neglected.The research on the adaptation potential of the mining restoration vegetation to heavy metal contaminated soil and its response to the environment needs to be further strengthened.In order to reveal,under different heavy metal pollution levels,the adaptation mechanism of native plants in Jinchuan mining area,this study adopts the Li-6400 photosynthetic apparatus and chlorophyll fluorescence instrument to measure the photosynthesis,fluorescence parameters and water use efficiency,etc.of the annual herb of the Jinchuan mining area and fit the best model.The response mechanism of the desert plant Halogeton glomeratus under heavy metal stress was preliminarily revealed,which provided a theoretical reference for vegetation restoration and heavy metal pollution alleviation in Jinchuan mining area.The main results are as follows:1.Under the single stress conditions of heavy metals Cr,Pb and Zn,the relative low concentration promote the germination rate(Cr?160mg/L,Pb?100mg/L,Zn?100mg/L)and germination trend of the seeds of the Halogeton glomeratus(Cr?80mg/L,Pb?100mg/L,Zn?50mg/L).On the contrary,the relative high concentration inhibits its germination rate(Cr?320mg/L,Pb?200mg/L,Zn?200mg/L)and germination trend(Cr?160mg/L,Pb?200mg/L,Zn?100mg/L).2.Under the stress of Cr,the contents of chlorophyll and malondialdehyde(MDA)in the seedlings of Haloxypyron sinense increased first and then decreased,and the low concentration promoted the synthesis of chlorophyll,but the high concentration decreased it.When the concentration of Cr was 320mg/L,the MDA was at its maximum,then decreased,but it was still higher than the control.It indicated that the concentration exceeds the tolerance range of the Halogeton glomeratus to chromium,leading a stress response,which increased the MDA content greatly,but as the concentration increased,the seedlings gradually adapted to the high concentration of chromium.The low concentration of Cr treatment promoted POD activity,and the high concentration of Cr stress inhibited POD activity.It indicated that the Halogeton glomeratus can resist the stress of Cr by enhancing the activity of antioxidant enzymes to a certain extent,showing some limited tolerance.Compared with the control,Under the stress of Cr,the proline content of the Halogeton glomeratus increased first then decreased.3.Under the stress of Pb,the chlorophyll content of Haloxypyron hirsutum seedlings increased first and then decreased;The content of MDA increased generally,indicating that with the increase of Pb concentration,the stress of the Halogeton glomeratus seedlings was enhanced,but the high concentration of Pb has a toxic effect on plant leaves.With the increase of Pb stress seriously,the activity of POD in leaves of Haloxypyron hirsutum increased first and then decreased.The low concentration of Pb treatment promoted the activity of POD.In addition,the high concentration of Pb treatment inhibited the activity of POD.Under the Pb stress,the proline content of the Halogeton glomeratus was irregular.4.Under the condition of Zn stress,the chlorophyll content and MDA content of the Haloxypyron sinense seedlings increased first and then decreased.it indicated that the low content promoted the synthesis of chlorophyll but the high content was the opposite.With the increase of Zn stress,the activity of POD in leaves of Halogeton glomeratus showed a trend of increasing,indicating that POD activity increased and maintained at a high level under zinc stress.The content of proline in Halogeton glomeratus had no obvious regularity under Zn stress.5.The fitting results of different models on the light response curve of the same plant are quite different,but the non-orthogonal hyperbolic model has the best fitting effect on the Halogeton glomeratus.The photosynthetic capacity of the Halogeton glomeratus in the Longshou mining area is stronger than the Xiasifen.Under different circumstances,the diurnal variation of net photosynthetic rate of Halogeton glomeratus had the phenomenon of “midday depression of photosynthesis”,and the phenomenon of “midday depression of photosynthesis” was mainly affected by non-stomatal limiting factors.In the Xiasifen and Longshou Mine,the maximum peak daily variation of net photosynthetic rate of Halogeton glomeratus appeared at around 10:00 and 16:00.The diurnal variation of net photosynthetic rate of Halogeton glomeratus in Longshou mining area was higher than that in the lower four points.Under different heavy metal concentration gradients,the initial fluorescence Fo decreased gradually with the increase of heavy metal concentration,and NPQ showed a downward trend.Yield was the increasing trend indicates that,with the increase of heavy metal concentration,it does not cause damage to the light system of the Halogeton glomeratus plant,indicating that in the Longshou mining area,the Halogeton glomeratus can better adapt to the local environment and has certain restrictions on heavy metals.Tolerance.It is indicated that in this experiment,the concentration of heavy metals is high,and the more favorable the light energy of the Halogeton glomeratus is for the photosynthetic electron transfer.6.Under different heavy metal concentration gradients,with the increase of heavy metal concentration,the spectral reflectance of the Halogeton glomeratus increased in the near infrared region and green peaks.The red edge amplitude of the Halogeton glomeratus in Longshou Mine is higher than the Xiasifen.The red edge position of Longshou Mine is blue-shifted relative to the lower four points.On the whole,with the increase of heavy metal concentration,the red edge amplitude of the reflection spectrum of the Halogeton glomeratus has increased,and the red edge position has a blue shift.