Abstract
Chromium (Cr) is among the most widespread toxic trace elements found in agricultural soils due to various anthropogenic activities. However, the role of micronutrient-amino chelates on reducing Cr toxicity in crop plants was recently introduced. In the current experiment, the exogenous application of micronutrients [iron (Fe)] chelated with amino acid [lysine (lys)] was examined, using an in vivo approach that involved plant growth and biomass, photosynthetic pigments and gaseous exchange parameters, oxidative stress indicators and antioxidant response. The uptake and accumulation of Fe and Cr were determined under different levels of tannery wastewater (33, 66, 100%) used along with the exogenous supplementation of Fe-lys (5 mM) to Spinacia oleracea plants. Results revealed that tannery wastewater in the soil decreased plant growth and growth-related attributes, photosynthetic apparatus and Fe contents in different parts of the plants. In contrast, the addition of different levels of tannery wastewater to the soil significantly increased the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and electrolyte leakage (EL), which induced oxidative damage in the roots and leaves of S. oleracea plants. However, S. oleracea plants increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), which scavenge the over-production of reactive oxygen species (ROS). Cr toxicity can be overcome by the supplementation of Fe-lys, which significantly increased plant growth and biomass, improved photosynthetic machinery and increased the activities of different antioxidative enzymes, even in the plants grown under different levels of tannery wastewater in the soil. Furthermore, the supplementation of Fe-lys increased the contents of essential nutrients (Fe) and decreased the contents of Cr in all plant parts compared to the plants cultivated in tannery wastewater without application of Fe-lys. In conclusion, the application of Fe-lys is an innovative approach to mitigate Cr stress in spinach plants, which not only increased plant growth and biomass but also decreased the Cr contents in different plant organs.
Highlights
Heavy metals are omnipresent pollutants of the environment, and their unnecessary level in arable soil can pose serious threats to normal plant growth and development, and to human health [1,2,3,4]
A maximum decrease in plant height, number of leaves, leaf area, root length, root fresh weight, root dry weight, leaf fresh weight and leaf dry weight by 52.8, 47.5, 79.7, 48.2, 56.7, 55.0, 67.7 and 68.8%, respectively, was recorded in the plants grown in 100% addition of tannery wastewater without the application of Fe-lys
Compared to the control treatment, maximum contents of MDA, H2O2 initiation and electrolyte leakage (EL) (%) were shown in the plants grown in 100% addition of tannery wastewater in the soil, which increased 3.9, 1.8 and 3.6 times, respectively, in the roots and 2.6, 3.4 and 3.2 times, respectively, in the leaves
Summary
Heavy metals are omnipresent pollutants of the environment, and their unnecessary level in arable soil can pose serious threats to normal plant growth and development, and to human health [1,2,3,4]. In some developing countries, such as Pakistan, aquifers were pooped from industrial sources into the water bodies, which were mixed in canals used for field irrigation [6,13] This wastewater needs to be investigated, and some artificial methods should be used to help impart crop yield and productivity. Cr is a major toxic element discharged into the environment through various industries, such as tanning, electroplating, manufacturing of pigments, production of nuclear weapons and corrosion control [18,19,20] This extensive industrial use of chromium composites and their subsequent releases, without prior treatment, into the surrounding environment contaminates the entire ecosystem and can lead to catastrophic health risks [21,22]
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