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Glandless cotton can be grown to obtain cotton seeds free of toxic gossypol for use as both food and feed. However, they are not grown normally due to their lesser productivity and higher susceptibility to biotic stress. Great attention has been paid to biotic stresses rather than abiotic stresses on glandless cotton. Chromium (Cr) is a common pollutant of soil and considered a serious threat to plants due to its adverse effects on different functions. Although numerous studies are available on the toxicity of Cr 6+ in various plants. However, its adverse effects and mechanism of toxicity in glandless cotton can seldom be found in the literature. This study examined the Cr 6+ effect on glandless cotton in comparison to glanded cotton. Four pairs of glanded and glandless cotton near-isogenic lines (NILs) were exposed to different doses (0, 10, 50, and 100 μM/L) of Cr 6+ for seven days, and biochemical, physiological, molecular, and ultrastructure changes were observed, which were significantly affected by Cr 6+ at high concentrations in all NILs. The effect of Cr 6+ on ionic contents shows the same trend in glanded and glandless NILs except for manganese (Mn 2+ ) that show inhibition in glandless (ZMS-12w and Coker-312w) and enhance in the glanded NIL (ZMS-17). The gene expression of superoxide dismutase (SOD) and peroxidase (POD) revealed similar trends as enzyme activities in glandless NILs. The principal component analysis (PCA) and Agglomerative hierarchical clustering (AHC) results of all NILs from morpho-physiological traits, cluster ZMS-16, and ZMS-17 into Cr 6+ sensitive group. While the glandless NILs have the potential to cope with the Cr toxicity by increasing the antioxidant enzyme activity and their gene expression. This study also revealed that Cr 6+ tolerance in cotton is genotypic and has an independent mechanism in the root that not related to low gossypol., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Chromium (Cr) stress is one of the most adverse environmental factors that affect plant growth and food chain contamination. Fulvic acid (FA) is known to enhance the growth and production of crops, but the studies are scare regarding the application of FA on metal tolerance in plants. The effects of FA application on alleviating Cr phytotoxicity in wheat plants were investigated in a pot experiment conducted in sand- and soil-grown plants. Three Cr (0, 0.25, and 0.50 mM) treatments in the form of K2Cr2O7 were applied in both soils with or without foliar application of 1.5 mg L(-1) FA. Plants were harvested after 4 months of treatments, and data regarding growth characteristics, biomass, photosynthetic pigments, and antioxidant enzymes were recorded. FA application increased plant biomass, photosynthetic pigments, and antioxidant enzymes while it decreased Cr uptake and accumulation in plants as compared with Cr treatments alone. We conclude that FA application contributes to decreased Cr concentrations in wheat grains and could be used as an amendment when aiming for decreased metal concentration in plants.

Glandless cotton can be grown to obtain cotton seeds free of toxic gossypol for use as both food and feed. However, they are not grown normally due to their lesser productivity and higher susceptibility to biotic stress. Great attention has been paid to biotic stresses rather than abiotic stresses on glandless cotton. Chromium (Cr) is a common pollutant of soil and considered a serious threat to plants due to its adverse effects on different functions. Although numerous studies are available on the toxicity of Cr6+ in various plants. However, its adverse effects and mechanism of toxicity in glandless cotton can seldom be found in the literature. This study examined the Cr6+ effect on glandless cotton in comparison to glanded cotton. Four pairs of glanded and glandless cotton near-isogenic lines (NILs) were exposed to different doses (0, 10, 50, and 100 μM/L) of Cr6+ for seven days, and biochemical, physiological, molecular, and ultrastructure changes were observed, which were significantly affected by Cr6+ at high concentrations in all NILs. The effect of Cr6+ on ionic contents shows the same trend in glanded and glandless NILs except for manganese (Mn2+) that show inhibition in glandless (ZMS-12w and Coker-312w) and enhance in the glanded NIL (ZMS-17). The gene expression of superoxide dismutase (SOD) and peroxidase (POD) revealed similar trends as enzyme activities in glandless NILs. The principal component analysis (PCA) and Agglomerative hierarchical clustering (AHC) results of all NILs from morpho-physiological traits, cluster ZMS-16, and ZMS-17 into Cr6+ sensitive group. While the glandless NILs have the potential to cope with the Cr toxicity by increasing the antioxidant enzyme activity and their gene expression. This study also revealed that Cr6+ tolerance in cotton is genotypic and has an independent mechanism in the root that not related to low gossypol. Image 1 • Chromium (Cr) adversely affects plant growth and root morphology. • Cr impaired nutrients uptake and enhance H 2 O 2 that leads to ultrastructure damages. • Cr-induced phytotoxicity varied among cotton near-isogenic lines (NILs). • Glandless cotton shows more resistance to Cr stress as compared to glanded cotton. [ABSTRACT FROM AUTHOR]