| The Iris germanica is a perennial herb of the iris family of the iris family,which has high ornamental value and absorption and enrichment effects.With the development of the flower industry,the demand for iris plants is increasing.In this study,the Iris germanica was used as the material,the plant cultivation soil was treated with different concentrations of heavy metal cadmium?Cd?,and the chelating agent ethylenediaminetetraacetic acid?EDTA?and bacterial fertilizer were added to observe the growth status of the plant and determine the plant?Divided into roots and leaves?physiological indicators,heavy metal cadmium content and the content of each subcellular component,observe the damage of the leaves.By studying the toxic effects and laws of cadmium at the tissue and subcellular levels of Iris germanica,the mechanism of Iris germanica tolerance to cadmium is analyzed to provide a theoretical basis for understanding the Iris germanica ability to accumulate heavy metals,tolerance mechanisms and stress physiology.The main findings are as follows:1)The highest biomass of Iris germanica is 11.14 g.pot-1 when the concentration of cadmium is 5 mg·kg-1,and the highest is 4.38 mg·g-1 when the chlorophyll content is 10mg·kg-1 for 45 days.The increase of EDTA concentration showed a significant difference in dry weight,and the root-to-root ratio decreased with the increase of Cd concentration;Cd concentration was 15 mg·kg-1,the content of chlorophyll a,b and carotenoid decreased significantly with the increase of EDTA concentration,the total chlorophyll content was 30 days The amount increased significantly,the highest was 4.64 mg·g-1.With the application of bacterial fertilizer,the plant height of 20 g·L-1 changed under different Cd concentrations.However,when the concentration is higher,the plant height changes greatly and the value decreases with the increase of Cd concentration.High concentration heavy metal stress injury.2)The activities of superoxide dismutase?SOD?,peroxidase?POD?and catalase?CAT?were highest at a Cd concentration of 10 mg·kg-1,and malondialdehyde?MDA?at30 d and 45 d.At 30 days,when the Cd concentration was 15 mg·kg-1,the content increased by 50%compared with the control,and the proline content increased by 24.3%compared with the control.When EDTA was applied,the activities of 5 mg·kg-1 and 10mg·kg-1 of the leaves decreased compared with the control.The SOD,POD and CAT activity of the leaves decreased.At 5 mg·kg-1,the soluble protein content increased with the concentration of EDTA.And the content rises.The proline content of 5 mg·kg-1decreased in different periods.The change of MDA with EDTA concentration after 45days was significantly different from the corresponding control.With the application of bacterial fertilizer,the activity was weak at the concentration of 20 g·L-1,and the CAT activity increased with the increase of concentration.When the Cd concentration was 10mg·kg-1 and 15 mg·kg-1,the MDA content increased.3)With the application of cadmium only,the accumulation of 5 mg·kg-1 aboveground Cd was 0.78 mg·kg-1,and the accumulation of 15 mg·kg-1 above 2.46mg·kg-1,so that the root Cd was transferred to the aboveground.The root organ Cd content of 5 mg·kg-1 was higher than that of the leaf,but with the increase of Cd concentration,the leaf was higher than the root.The accumulation site of 15 mg·kg-1Cd was mainly the leaf.The enrichment ability of bacterial manure was higher than that of EDTA at 5 mg·kg-1Cd treatment,and the stronger enrichment ability of EDTA at 15mg·kg-1 was 5.26 mg·kg-1.The Cd content of the same subcellular component in different organs is consistent with the total Cd content in each organ,that is,root>leaf.Bacterial manure treatment,at a concentration of 5 mg·kg-1Cd,40 g·L-1 bacterial manure makes the plant transfer coefficient higher than the corresponding control group,so Cd is mainly distributed in the cell wall and cell matrix,and the low concentration of root subcellular Cd content is higher than that in leaves The Cd content of high concentration leaf subcellular is higher than that of root system.4)Scanning electron microscope?SEM?results are as follows:Iris germanica leaf damage mainly showed epidermal shrinkage,xylem ring damage,cortical duct blockage,and overall structure damage.In the control?A0?,the surface of the leaf tissue is smooth and continuous,the xylem ring is clear,and the arrangement is neat and without damage;the phloem structure is full and the contour is clear.The EDTA treated leaf epidermal cells shrank,and the high-concentration Cd leaves showed large damage;the xylem ring was fuzzy and broken;the cortex showed granular crystals and some ducts were blocked.The bacterial epidermis treated with low-concentration Cd leaves had a small change in the epidermis,the high-concentration epidermal cells shrank seriously,and there were spherical protrusions locally.The Cd concentration was 15 mg·kg-1.The connecting wall between adjacent cells is difficult to identify,and it is difficult to distinguish structures such as phloem and xylem. |
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