Phyto-management of chromium contaminated soils through sunflower under exogenously applied 5-aminolevulinic acid.
Soil contamination with heavy metals is threatening the food security around the globe. Chromium (Cr) contamination results in poor quality and reduction in yield of crops. The present research was performed to figure out the Cr toxicity in sunflower and the ameliorative role of 5-aminolevulinic acid (ALA) as a plant growth regulator. The sunflower (FH-614) was grown under increasing concentration of Cr (0, 5, 10 and 20mgkg-1) alone and/or in combination with 5-ALA (0, 10 and 20mgL-1). Results showed that Cr suppressed the overall growth, biomass, gas exchange attributes and chlorophyll content of sunflower plants. Moreover, lower levels of Cr (5 and 10mgkg-1) increased the production of reactive oxygen species (ROS) and electrolyte leakage (EL) along with the activities of antioxidant enzymes i.e., superoxide dismutase (SOD), guaiacole peroxidase (POD), ascorbate (APX), catalase (CAT). But at higher concentration of Cr (20mgkg-1), the activities of these enzymes presented a declining trend. However, the addition of 5-ALA significantly alleviated the Cr-induced toxicity in sunflower plant and enhanced the plant growth and biomass parameters along with increased chlorophyll content, gas exchange attributes, soluble proteins and soil plant analysis development (SPAD) values by scavenging the ROS and lowering down the EL. The 5-ALA also enhanced the activities of antioxidant enzymes at all levels of Cr. The increase in Cr concentration in all plant parts such as leaf, root and stem was directly proportional to the Cr concentration in soil. The application of 5-ALA further enhanced the uptake of Cr and its concentration in the plants. To understand this variation in response of plants to 5-ALA, detailed studies are required on plant biochemistry and genetic modifications.
Farid M
，Ali S
，Rizwan M
，Ali Q
，Saeed R
，Nasir T
，Abbasi GH
，Rehmani MIA
，Ata-Ul-Karim ST
，Bukhari SAH
，Ahmad T
... -
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Role of iron-lysine on morpho-physiological traits and combating chromium toxicity in rapeseed (Brassica napus L.) plants irrigated with different levels of tannery wastewater.
Chromium (Cr) is among the most widespread toxic trace elements found in agricultural soils resulting from various anthropogenic activities. However, the role of micronutrient-amino acid chelates in reducing Cr toxicity in crop plants has recently been suggested. The present study was conducted to explore the effect of iron (Fe) chelated with lysine (lys) on plant growth, biomass, gaseous exchange attributes, oxidative stress indicators, antioxidant response, and Cr uptake in rapeseed (Brassica napus L.) plants irrigated with different levels of tannery wastewater in soil collected from District Kasur of Pakistan. B. napus seedlings (thirty-day-old) were shifted to pots irrigated with different levels of tannery wastewater. After two weeks, foliar application of Fe-lys (5 mM) was carried out for four successive weeks, and plants were harvested carefully post ten weeks of cultivation in tannery wastewater, under controlled conditions. Toxic levels of Cr in the soil significantly decreased plant height, fresh biomass of roots and leaves, dry biomass of roots and leaves, root length, number of leaves, leaf area, total chlorophyll contents, carotenoid contents, transpiration rate (E), stomatal conductance (gs), net photosynthesis (PN), and water use efficiency (WUE). Toxic Cr levels in the soil also increased oxidative stress in the roots and leaves of B. napus plants, which were overcome by the activities of various antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Moreover, increasing levels of Cr in the soil caused a significant increase in the Cr content of the roots and shoots of B. napus plants. The negative effects of Cr toxicity could be overturned by Fe-lys application, significantly increasing plant growth, biomass, chlorophyll content, and gaseous exchange attributes by reducing oxidative stress (H2O2, MDA, EL) and enhancing antioxidant enzyme activities. Furthermore, foliar application of Fe-lys reduced the Cr concentration and increased essential micronutrients (Fe contents) in the roots and shoots of B. napus plants. These results shed light on the effectiveness of Fe-lys in improving the growth and up-regulation of antioxidant enzyme activities of B. napus in response to Cr stress. However, further studies at field levels are required to explore the mechanisms of Fe-lys-mediated reduction of the toxicity of not only Cr, but possibly also other heavy metals in plants.
Zaheer IE
，Ali S
，Saleem MH
，Imran M
，Alnusairi GSH
，Alharbi BM
，Riaz M
，Abbas Z
，Rizwan M
，Soliman MH
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