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Variations in morphological and physiological traits of wheat regulated by chromium species in long-term tannery effluent irrigated soils

Riaz, Muhammad, Yasmeen, Tahira, Arif, Muhamad Saleem, Ashraf, Muhammad Arslan, Hussain, Qaiser, Shahzad, Sher Muhammad, Rizwan, Muhammad, Mehmood, Muhammad Waqas, Zia, Afia, Mian, Ishaq A., Fahad, Shah
Chemosphere 2019 v.222 pp. 891-903
agricultural soils, bioaccumulation factor, carotenoids, chlorophyll, chromium, growth and development, organic carbon, organic fertilizers, physiological response, phytotoxicity, plant growth, pollution, soil sampling, tannery effluents, wastewater irrigation, wheat, Pakistan
Tannery effluents are rich source of chromium (Cr) and organic carbon (C), however, hexavalent Cr (Cr6+) is many-fold more toxic than trivalent Cr (Cr3+). We examined the extent of total Cr, Cr3+ and Cr6+ pollution of agricultural soils under long-term tannery effluent irrigation in Kasur, Pakistan. Effects of Cr species on morphological and physiological responses of wheat including patterns of Cr3+ and Cr6+ uptake, their translocation factor (TF) and bioconcentration factor (BCF) were studied. Nine soil samples had significantly variable total organic C and total Cr, Cr3+ and Cr6+ contents. Pot study showed that morphological characteristics of wheat were largely unaffected by total Cr, Cr3+ and Cr6+ contents, however, physiological responses including contents of chlorophyll a, chlorophyll b, total chlorophyll, carotenoids and total proteins; and chlorophyll a:b ratio were significantly affected by contents of Cr species. Results further suggested that the relationships between total Cr and physiological attributes of wheat were controlled by Cr6+ rather than Cr3+ contents and, hence, Cr3+:Cr6+ ratios determined the effects of Cr on wheat growth and development. Uptake, TF and BCF values for Cr3+ and Cr6+ showed significant variations and BCF values showed negative correlation with total organic C contents. Results of our study highlight the significance of understanding the effects of Cr species and Cr3+:Cr6+ ratios rather than the total Cr contents when assessing the Cr behavior in soils and its effects on plant growth, especially phytotoxicity of tannery-based organic fertilizers before its application in the field.