Impact of zinc oxide nanoparticles on green pea plant and seed quality and effects on physiological traits of green peas, corn, and zucchini by silver nanoparticles.

摘要

This project was completed in four phases. In Phase I, the green pea plants (P. sativum L.) were exposed to 0, 125, 250, and 500 mg kg--1 of 10 nm bare ZnO NPs and bulk ZnO for 25 days in organic matter enriched soil (native soil: potting soil= 1:1) in a growth chamber. Toxicological effects were investigated in terms of plant growth, chlorophyll production, zinc accumulation in different tissues, reactive oxygen species/ROS (H2O2) generation, stress enzyme activity (catalase/CAT and ascorbate peroxidase/APOX), and lipid peroxidation. Root elongation reduction (48-52%) was observed in all ZnO NP concentrations ( p ≤ 0.05); however, stem lengths were unaffected compared to control. Chlorophyll in leaves decreased, compared to the control, by 61%, 67%, and 77% in plants treated with 125, 250, and 500 mg kg--1 ZnO NPs, respectively. Bulk ZnO treatments also showed similar results. In roots and leaves, APOX activity decreased in both nano and bulk treatments. However, in leaves, CAT activity decreased in NP treatments but remained unaltered with addition of bulk ZnO. In leaves, there was a 61% increase in H2 O2 production with a twofold increase in lipid peroxidation. From this study, it may be concluded that the nano form of ZnO is more toxic than the bulk form under the growth conditions of this study. Phase II was designed to evaluate the toxicological effects of 10% Fe ZnO NPs on green peas at 0, 125, 250, and 500 mg kg--1 concentrations for 25 days in similar soil type and similar growth conditions. Results were compared with that of Phase I. At 500 mg kg--1, zinc bioaccumulation was increased in both root (200%) and stem (31-48%), compared to control, without affecting the iron uptake (p ≤ 0.05). Chlorophyll content and H2O2 production decreased by 27% and ∼50%, respectively (p<0.05), compared to control. Fe ZnO showed less toxicity than that of bare-ZnO NPs under the applied growth conditions as indicated by zinc bioaccumulation, chlorophyll production, and H2O2 production. Therefore, iron doping can be considered as a safer approach to reduce toxicity of ZnO NPs in terrestrial plants. Phase III was focused on phyto-toxicological studies of bare-ZnO NPs, alumina ZnO NPs, and ZnO KH550 NPs on green pea plant, its life-cycle, and seeds. The plants were grown in a greenhouse with continuous supply of nutrients (fertilizer) in the similar 1:1 organic matter enriched soil for 65 days. Upon harvest, different physiological and biochemical parameters, e.g., fresh and dry weights, leaf chlorophyll a, b, leaf carotenoids, zinc bioaccumulation, protein and carbohydrate profiles were measured in different parts of the plant, as applicable. No change in plant fresh and dry weights with treatments were observed, except with ZnO KH550 at 1000 mg kg--1 treatment, which showed about one fold (95%) increase in plant fresh weight compared to control. Plant roots showed a significant increase in Zn accumulation of 5.7x, 5.7x, and 8x treated with 250 mg kg--1 bulk ZnO, bare ZnO NP, and Al2O3 ZnO NP respectively, compared to controls. Similarly, at 1000 mg kg --1, bare ZnO NP and Al2O3 ZnO NP treatments showed significant increases in zinc uptake up to 16x and 36x times compared to controls. Green pea stems showed higher level of Zn accumulation, except with the ionic zinc treatment. The Zn accumulation was in this order: [at 250 mg kg--1 : bulk (5x), bare (7x), doped (4.7x) and coted (7x); at 1000 mg kg --1: bulk (9x), bare (11x), doped (20x) and coted (9x)] compared to control. In leaves, all the treatments (bulk and coated) showed significant increase in zinc uptake (4.6x to 5.3x) except at 250 mg kg--1 and 500 mg kg--1 treatments. The1000 mg kg --1 treatments (bulk, bare, and doped) also showed significant increase in zinc uptake (5.5x to 11x) except for coated and ionic treatments. The aluminum and silicon uptake did not change with one exception at 1000 mg kg--1. Amount of chlorophyll-a (Chl-a) was significantly increased at 250 mg kg--1 alimina doped treatment (4.5x) and in all the treatments at 1000 mg kg--1 [bulk (3.2x), bare (2.7x), doped (3.6x), coted (2.5x), and ionic (2.4x)] compared to control. However, there was no difference in the amount of chlorophyll-b (Chl-b) was observed. The total carotenoid was increased significantly at 250 mg kg --1 to 10x in doped and 7x times in ionic treatment. The increase was 7.6x in bulk and 8.6x in case of doped NPs at 1000 mg kg--1 treatments. (Abstract shortened by UMI.).