| The effects of veterinary drug residues of ROX and CUSO4 in soil on the seed germination, seedling growth and physiological and biochemical changes, ion-selective absorption and transportation, food quailty and food safety etc. on leaf vegetables were examined and analysized in this paper with Ipomoea aquatic and Amaranthus mangostanus as experimental materials. The results are as follows:I. Effects of ROX onⅠ. aquatic and A. mangostanus1. Seed germinationCompared with the control, the germination ofⅠ. aquatic and A. mangostanus seeds were inhibited significantly by ROX. Results from the tolerance analysis showed that the relative vigor index was more suitable to represent their germination quality. The semi-lethal and lethal concentrations ofⅠ. aquatic seeds to ROX, which were calculated upon the relative vigor index, were 1.02mM and 1.72mM respectively; and the semi-lethal and lethal concentrations of A. mangostanus seeds, were 0.64mM and 1.76mM respectively. According to this result, about half or above of I. aquatic seeds can germinate in heavily ROX-polluted areas and A. mangostanus seeds were more sensitive to ROX than I. aquatic seeds.2. Seedling growth, physiological and biochemical changesA. Growth and photosynthesisThe growth ofⅠ. aquatic and A. mangostanus seedlings were inhibited significantly by ROX treatment. With the increasing of ROX concentration, plant height, leaf area, fresh weight and dry weight etc. of both seedlings decreased, and the inhibition extents on roots were higher than those on shoots, the roots of groups were blackened and ulcerated. The contents of Chl and Car in the upper leaves (position 3-4) of both seedlings decreased sharply under ROX treatment. The initial chlorophyll fluorescences (Fo) under ROX were higher than the control, maximum fluorescence yields (Fm) showed no significant difference, and the potential photosynthetic capacities of PSⅡ(Fv/Fo) and maximal quantum yields (Fv/Fm) decreased significantly with ROX increase. These results showed that the actual photochemical efficiency of PSⅡof both seedlings decreased under ROX.B. ROS generation and ROS scavengingCompared with the control, the ROS (O2-.and H2O2) accumulated and antioxidases'activities were enhanced in the leaves of I. aquatic and A. mangostanus seedlings under ROX treatments. Activities of SOD, POD, CAT and APX were always higher than the control in the leaves ofⅠ. aquatic; while in the leaves of A. mangostanus, activities of SOD, POD and APX were significantly higher than the control only when ROX>1mM, and CAT activity was always higher than the control. In addition, the higher the ROX concentration, the higher the contents of AsA, GSH, anthocyanin, with the exception of Car content, in both seedlings. The increased ROS scavenging ability could not scavenge the highly accumulated ROS. As a result, with ROX increase, MDA accumulated and membrane permeability increased gradually, which demonstrated that both seedlings were damaged by ROX treatment.C. The absorption, allocation and transportation of ionsWith the increase of As, As content increased in all organs of both seedlings and accumulated mainly in roots. Contents of P, K, Mn, Zn and Cu in both seedlings increased under 8mM ROX concentrations and decreased under 12mM ROX concentrations. With the increase of ROX concentration, contents of Ca, Mg and some trace elements in all organs of both seedlings decreased. Furthermore, both seedlings'abilities on ion-selective absorption and transportation of K, Ca, Mg of were affected to a certain extent by ROX treatment.3. Food quality and food safetyAs contents in all organs ofⅠ. aquatic and A. mangostanus seedlings under ROX treatments all exceeded the standard of national minimum limits. The nitrate contents in the leaves of both seedlings reached the moderate pollution level. Under the ROX treatment, carbohydrate content increased, soluble protein and free amino acids contents decreased in the leaves ofⅠ. Aquatic seedlings; while in the leaves of A. mangostanus, the contents of carbohydrate and free amino acids showed no changes and soluble protein contents increased slightly. In addition, the contents of Vc and anthocyanin in both leaves increased and Car contents decreased.Overall, ROX treatment led to a sharp increase of toxic As and nitrate and a decrease of most healthful substance decreased in the edible parts of bothⅠ. aquatic and A. mangostanus seedlings.Ⅱ. Effects of CUSO4 onⅠ. aquatic1. Seed germination ofⅠ. aquatic and A. mangostanusCompared with the control, little effect was found of CUSO4 treatment on the germination rates of both seeds, but the growth of radicles and hypocotyls of both seeds were seriously inhibited, and the inhibition extent on the radicles was higher than that on hypocotyls. According to the correlation analysis on relative vigor index, the semi-lethal and lethal concentration ofⅠ. aquatic seeds under CUSO4 treatment were 1.41mM and 5.12mM respectively; and the semi-lethal and lethal concentration of A. mangostanus seeds were 0.1289mM and 0.751mM respectively. This showed that A. mangostanus seeds were more sensitive to CUSO4.2. Seedling growth and physiological and biochemical changes ofⅠ. aquatic seedlingsA. Growth and photosynthesis From the appearance, shoot growth ofⅠ. aquatic seedlings was promoted at 1mM CuSO4, and inhibited when CuS04>1mM. Plant height, leaf area, fresh weight and dry weight etc. ofⅠ. aquatic seedlings all decreased with the increase of CuSO4 concentration. The root elongation was hindered, the number of root hairs reduced under CUSO4. Chla and Car contents, Chla/b and Car/Chlt values in the upper leaves (position 3-4) ofⅠ. aquatic seedlings changed little under CUSO4 treatments, Chlb contents was significantly lower than the control when CuSO4=9mM. With the increase of CUSO4 concentration, the initial chlorophyll fluorescence (Fo) increased, maximum fluorescence yield (Fm), potential photosynthetic capacity of PSⅡ(Fv/Fo) and maximal quantum yield (Fv/Fm) decreased. These results showed that the photosynthetic capacity ofⅠ. aquatic seedlings was retarded.B. ROS generation and ROS scavenging ofⅠ. aquatic seedlingsCompared with the control, CUSO4 treatment led to the ROS accumulation in the leaves ofⅠ. aquatic seedlings. SOD activity increased prouncedly, and activities of POD, CAT and APX increased with the increase of CUSO4 concentration (r=0.944,0.897, and 0.982 respectively). Contents of AsA, GSH and anthocyanin increased to different degrees and Car content changed little under CUSO4 treatment. The synergy among various antioxidases and small anti-oxidant molecules cleared the excess accumulated ROS, and the damage of CuSO4 on the cell membrane was not evident.C. The absorption, allocation and transportation of ions ofⅠ. aquatic seedlingsCu content increased in all 3 organs ofⅠ. aquatic seedlings with the increase of CUSO4 treatments, and Cu accumulated mainly in roots. The total content of the macro elements changed little when CUSO4< 6mM and decreased at 9mM CUSO4 with the decrease of Ca and Mg contents more obviously. Trace element content in roots and stems changed little, but in leaves it decreased gradually when CUSO4 ranged from 6mM to 9mM. In addition, the absorptive capacity ofⅠ. aquatic seedlings from soils on K+, Ca2+ and Mg2+ decreased when CUSO4 ranged from lto 6mM, but increased at 9mM CUSO4.3. Food quality and and food safetys ofⅠ. aquatic seedlingsCu contents in the stems and leaves ofⅠ. aquatic seedlings under CUSO4 treatments didn't exceed the standard of national minimum limits, but in the roots it exceeded greatly. Nitrate content in leaves exceeded the standard when CuSO4>1mM. The contents of carbohydrate, soluble protein and Car etc changed insignificantli under CuSO4 treatment; the contents of Vc and anthocyanin increased and free amino acids decreased under the CUSO4 treatment. According to the vegetable grading standards on nitrate content, we can infer that the stems and leaves ofⅠ. aquatic seedlings growing in the CuSO4-contaminated soil in our sountry are edible only aften being cooked. |
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