- Title
- Zinc and cadmium interactions on the growth, enzymatic antioxidants, metal partitioning and bioavailability of mung beans
- Creator
- Rashid, Md Harunur
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Cadmium (Cd) toxicity and zinc (Zn) deficiency are both serious problems to crop growth and quality. Moreover, the interactive effects between these two elements are complicated with conflicting reports suggesting synergistic as well as antagonistic effects of Zn on Cd. This PhD study was investigated to determine the Cd and Zn interactions in Mung bean varieties usually grown in Australia by addressing following questions: a) Can selected zinc oxide nanoparticles improve the plant growth, antioxidant enzymes by reducing Cd concentration in solution culture experiment? b) Can ZnSO4 supplement improve the plant growth, antioxidant enzymes in two contrast mung bean varieties by reducing Cd concentration in solution culture experiment? c) Can basal ZnSO4 supply improve the agronomic parameters, and photosynthetic pigments in mung beans grown in Dermosol and Tenosol under Cd stress? d) Can basal ZnSO4 supply influence metal distribution, Cd remediation in grains, and associated health risks? Several experiments were conducted to investigate the influence of Zn on Cd in mung beans (Vigna radiata L.) of which two are on hydroponic system and the other was on two soil types (Dermosol and Tenosol) with contrasting DTPA-Zn levels. Zinc oxide nanoparticles (ZnO NPs) was used in one of the hydroponic experiments. Nanotechnology is an emerging scientific technology, is considered to be an ideal solution to combat environmental pollution. The use of ZnO NPs has recently drawn much attention for their potential to enhance the accumulation of nutrients by plants and to ensure quality outcomes are produced. Seven-day-old seedlings were treated with various concentrations of Zn (0, 1, 2, 4, 8, 16 and 32 µM) and Cd (0, 0.5, 1 µM) for 14 days. Mung beans was grown up to 30 days in half-strength Hoagland solution to investigate the influence of added Zn and Cd contamination on photosynthetic pigments, antioxidant enzyme activities, yield parameters, metal partitioning. Another hydroponic experiment consists of Zn (as zinc sulfate) treatments (0, 1, 2, 4, and 8 µM), Cd treatments (0, 0.5, 1 µM) and two varieties of mung beans (Jade-AU and Celera II-AU). Photosynthetic pigments, antioxidant enzyme activities, dry matter yield and metal concentration in tissues were significantly influenced by added Zn and Cd contamination. Added ZnO NPs (up to 4 µM) to Cd contaminated media (0.5 and 1.0 µM of Cd) elevated the leaf Cd concentration, which was restricted by a higher supply of ZnO NPs. However, Cd accumulations in stem and root tissues consistently rose due to these interactions indicating a synergistic effect. ZnO NPs induced an upregulation of antioxidant enzymes to avert from oxidative stress and keep growth performance. Similar to the findings of ZnO NPs application, ZnSO4 as a Zn source also demonstrated enhanced antioxidant activities (e.g. up to 13% for APX, up to 41% for CAT, up to 40% for POD, and up to 35% for SOD) over control in both the varieties of mung bean varieties (Jade-AU and Celera II-AU) indicating the beneficial effect of Zn supply to escape oxidative stresses and maintain crop growth. Two soil types (Dermosol and Tenosol) were used for the other experiment encompassing Zn (0, 5, 10 and 20 mg kg-1) and Cd (0, 2, 4 mg kg-1) treatments. Soils were spiked with Cd and acclimatized for three months. Exogenous application of Zn through basal soil nutrition replenished yield loss due to Cd contamination (over 30%) through boosting up yield (up to 26%) and yield attributing characters of mung beans. Improved seed yield was due to significant increase in a greater number of pods, number of seeds per pod and 100 grain weight owing to high chlorophyll contents in mung beans leaves, increased Zn accumulation (67% higher in grain) and reduced Cd translocation (34% less in grain) in tissues. Amongst all applied Zn levels, the basal application @ 5 mg Zn/kg soil was a viable option to gain better yield, grain Zn biofortification and Cd remediation of mung bean for Cd contaminated soils. At control, Cd partitioning follows the order, e. g. root > stem > petiole > pod > leaflet > grain for both soils. However, Zn partitioning varied based on soil properties, such as, gain>leaflet>petiole>pod>root>stem and grain>leaflet>petiole>stem>root>pod for Dermosol and Tenosol, respectively. Consumption of mung bean grains grown did not demonstrate any non-carcinogenic effect for both children and adults as the EDI and PTDI values which were below the safety limit, however, the ILCR values exceeded it, indicating the possibility of some carcinogenic effect. Adding Zn helped reduce the non-carcinogenic and carcinogenic effects for humans.
- Subject
- zinc; cadmium; mung beans; growth
- Identifier
- http://hdl.handle.net/1959.13/1484430
- Identifier
- uon:51331
- Rights
- This thesis is currently under embargo and will be available from 27.06.2024, Copyright 2023 Md Harunur Rashid
- Language
- eng
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