Iron–Lysine Mediated Alleviation of Chromium Toxicity in Spinach (Spinacia oleracea L.) Plants in Relation to Morpho-Physiological Traits and Iron Uptake When Irrigated with Tannery Wastewater

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.

Zinc-lysine Supplementation Mitigates Oxidative Stress in Rapeseed (Brassica napus L.) by Preventing Phytotoxicity of Chromium, When Irrigated with Tannery Wastewater

“…In the current study, Cr toxicity caused oxidative stress in the B. napus by increasing malondialdehyde (MDA) content in the roots and leaves of the plants (Figure 2). This is because Cr toxicity disrupts the electron transport chain, producing much higher levels of H 2 O 2 and O −2 radicals and increasing electrolyte leakage afterwards [10]. Extremely high contents of Cr in the plants can decrease the activities of antioxidant enzymes, which was also noticed in the current experiment with the addition of 66% and 100% tannery wastewater in the soil, which decreased the activities of various antioxidant enzymes in B. napus significantly (Figure 3).…”

“…The harmful effects of heavy metals on food safety and marketability, plant growth because of plant-toxicity, and the ecosystem health of soil organisms cause serious metal accumulation in soils in agricultural production [ 32 , 33 ]. Like all living organisms, plants are very often both susceptible to the shortage and abundance of the available heavy metal ions as the key micronutrient, although they are also very toxic to normal plant growth and development at higher concentrations and even more ions such as Cr [ 7 , 10 ]. In our previous study, we also observed that the toxic concentration of Cu in the nutrient solution changed growth and other morphological attributes in the 40-day-old B. napus seedlings [ 18 ].…”

“…The results from the rapid uptake of Cr content by the plant organs caused stunned growth and declined biomass in all parts of the plants [ 34 ]. Furthermore, it was also noticed that a very high concentration of Cr in the soil decreased some essential nutrients in the soil, which are important for normal growth and development of a plant body [ 10 , 34 ].…”

“…Recently, various studies have indicated the imperious role of different amino acids in alleviating heavy metal stress in the various plants [ 10 ]. Zinc (Zn)-chelated fertilizer with amino acid, like lysine (lys), is documented to boost crop yield and production [ 3 , 11 ].…”

Peptone-Induced Physio-Biochemical Modulations Reduce Cadmium Toxicity and Accumulation in Spinach (Spinacia oleracea L.)

“…Such decreases in antioxidant enzymes activity might be due to the higher concentration of Cd in plants, which in turn increased the levels of EL and MDA. Additionally, the increase or decrease in the activity of antioxidant enzymes depends upon the level of metal stress and plant species [ 69 , 70 ]. In the present study, the application of peptone promoted the antioxidant enzymes activities.…”