| Aralia elata var.inermis is one of the precious woody vegetable resources, having thereputation of “ginseng”. In order to study the relation between the photosynthesis andecological factors of Aralia elata var.inermis, we chose Aralia elata var.inermis as theresearch material. And we used the open air cultivation and greenhouse cultivation methods.In addition, we added heavy metal (Pb、Cd) in the pot soil, and studied the effects of heavymetal on photosynthesis, chlorophyll content, nutritional quality, trace elements and otherphysiological characteristics. The aim of the experiment is to understand whether thephotosynthetic physiological and nutritional quality of Aralia elata var.inermis can beaffected under the treatment of Pb、Cd and provide certain theoretical basis for theintroduction and cultivation of Aralia elata var.inermis in Tianjin. The main results were asfollows:(1) The net photosynthetic rate of Aralia elata var.inermis in greenhouse cultivation washigher than the open air condition. In the open air condition, Pn increased firstly and thendecreased, and the trend showed a unimodal curve. The peak appeared at about10:00a.m,and was15.9μmol m-2s-1. While, the net photosynthetic rate of Aralia elata var.inermisshowed typical bimodal curve under greenhouse cultivation condition, and it existedphotosynthetic "noon break" phenomenon. The highest value occurred at about10:00a.m,andwas20.08μmol m-2s-1. In the correlation analysis, the ecological factors of Pn wasfollowed by photosynthetic active radiation (PAR), atmospheric temperature (Tair),atmospheric CO2(Ca) and relative humidity (RHin), physiological factor was stomatalconductance (Gs), transpiration rate (E), intercellular CO2concentration (Ci). When Tair wasover31℃, PAR was more than1700μmol m-2s-1, the photosynthesis of Aralia elatavar.inermis was restrained. In the multiple stepwise regression analysis, the mainphysiological factors affected the Pn wass Gs and Ci, ecological factors was Ca and RHin.(2) Low concentration of heavy metal (Cd) played an important role in promoting thesynthesis of chlorophyll a and chlorophyll b. At the concentration of2mg·kg-1, there weresignificant increases in net photosynthetic rate and transpiration rate. High concentration ofPb (≥1000mg kg-1) inhibited the synthesis of chlorophyll a. When the concentrations were1000,1500mg kg-1, the content of chlorophyll a increased, and the net photosynthetic rate ofAralia elata var.inermis decreased significantly at the concentration of1500mg kg-1.(3) The contents of soluble protein and soluble sugar increased firstly, and then thecontent decreased because of the increase of heavy metals (Pb, Cd) concentration. At the firstyear of stress, the content of soluble protein increased significantly at the concentration of100mg kg-1Pb and the concentration of1mg kg-1Cd. When treated in the concentration of1500mg kg-1Pb and2,5,10,20mg kg-1Cd, the content of soluble protein decreased significantly.While, at the second year of stress, the contents of soluble protein and soluble sugar showed a decline trend under the stress of Pb and Cd.(4) Stem bark had the highest content of trace element, followed by roots, leaves andstems. The content of Zn and Mn was the highest in the mature period (100days aftergermination), the Cu and Fe was the highest in seedling stage (20days after germination). Atthe first year, the content of Cu, Zn was higher than the control, while Mn and Fe presentedvolatility. At the second year of stress, the contents of Cu, Zn, Fe were lower than the firstyear, and the stress was more serious with the increased of Pb concentration. Under thetreatment of Cd, the content of Cu and Mn declined, the Zn increased firstlt and thendecreased, and Fe showed volatility. On the second year, the content of Cu, Zn, Fe decreasedexcept the Mn.(5) The accumulation of Pb was higher than Cd in Aralia elata var.inermis. Pb and Cdcontents were highest in root, followed by the stem, and the accumulation was the lowest inleaves. And the accumulation contents of heavy metal increased with the increasedd of heavymetal concentration. At the first year, the contents of Pb, Cd exceeded the national standardfor the quality of vegetables when the Pb was1000,1500mg kg-1, and the Cd was5,10,20mg kg-1, so the leave could not meet the consumption require. At the second year of stress, theheavy metal contents in plants declined when compared with the first year, making the leavescan be eat. Under the Pb stress，the enrichment coefficient of the ground and underground partincreased and then decreased with the increase of the heavy metal concentration. While, theenrichment coefficient of ground and underground part decreased. Under the Cd stress, theenrichment coefficient of underground part decreased, while ground part increased firstly andthen decreased. On the second year, the underground enrichment coefficient increased andthen decreased. |
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