24-Epibrassinolide mitigates nickel toxicity in young Eucalyptus urophylla S.T. Blake plants: nutritional, physiological, biochemical, anatomical and morphological responses

Abstract

& Key message Our research revealed that 24-epibrassinolide alleviated nickel toxicity in young Eucalyptus urophylla plants, inducing benefits on nutritional, physiological, biochemical, anatomical and morphological responses. & Context Soil contamination by heavy metals may limit the Eucalyptus production. Disturbances caused by nickel (Ni) toxicity interfere with the absorption of other essential nutrients. 24-Epibrassinolide (EBR) is one form of brassinosteroid (BR) that provides benefits for plant metabolism under Ni toxicity. & Aims The aim of this study was to determine whether exogenous EBR can improve ionic homeostasis by evaluating nutrient concentrations, anatomical characteristics and chlorophyll fluorescence in young Eucalyptus urophylla plants subjected to Ni toxicity. & Methods The experiment was randomized into four treatments, including two Ni concentrations (0 and 600 μM Ni) and two 24epibrassinolide concentrations (0 and 100 nM EBR). & Results EBR significantly reduced Ni contents. Plants exposed to Ni 2+ and sprayed with steroid had increases in the Ca 2+ /Ni 2+ and Mn 2+ /Ni 2+ ratios in the leaves of 38% and 15%, respectively, compared with the same treatment without EBR. The treatment of Ni 2+ toxicity + EBR presented an increase of 42% in effective quantum yield of PSII photochemistry, when compared with plants exposed to Ni without EBR. Ni toxicity induced negative effects on stomatal functionality, but EBR application mitigated these effects. & Conclusion Benefits on effective quantum yield of PSII photochemistry after EBR spray can be related to increases in manganese contents. EBR reduced oxidative stress, alleviating the deleterious effects induced by Ni toxicity and inducing positive repercussions on antioxidant enzymes, photosynthetic pigments and biomass.

Ionic Homeostasis and Redox Metabolism Upregulated by 24-Epibrassinolide are Crucial for Mitigating Nickel Excess in Soybean Plants, Enhancing Photosystem II Efficiency and Biomass

“…and Mn contents in shoot and root tissues Jan et al (2018). reported increases in macronutrient contents, more speci cally Mg, Ca and P, in Pisum sativum pretreated with EBR (individual or combined with silicon) under cadmium (Cd) stress.Ca 2+ /Ni 2+ , Mg 2+ /Ni + 2 and Mn 2+ /Ni 2+ ratios were increased after EBR spray in leaves, stems and roots.These results reveal multiple bene ts of this steroid on homeostasis, increasing ionic ratios and decreasing the stress generated by Ni(Reis et al, 2017;Ribeiro et al, 2020), con rmed by increases in Ca, Mg and Mn contents and other elements evaluated in this research Hu et al (2016). studied the EBR effects in Solanum tuberosum plants under salt stress conditions and described positive effects of this steroid on homeostasis connected to the K + /Na + ratio, combined with higher root e ciency and improvement in antioxidant capacity in shoots.Pretreatment with EBR minimized the impacts of Ni on F v , F m and F v /F m .…”

Ionic homeostasis and redox metabolism upregulated by 24‐epibrassinolide are crucial for mitigating nickel excess in soybean plants, enhancing photosystem II efficiency and biomass

“…Ribeiro et al . (2020) found significant increments in ionic ratios involving Ca and Mn after EBR treatment, which were linked to improved root anatomy and antioxidant system.…”

“…Ni excess often impacts biomass, which is correlated with inadequate uptake, transport and distribution of macro-and micronutrients (Matraszek et al, 2016), including strong limitations on the absorption of Mg, Mn, Zn and Fe (Palacios et al 1998;Torres et al 2016). Phytotoxicity linked to Ni negatively modulates photochemical e ciency (Ribeiro et al, 2020), gas exchange (Nazir et al, 2019), water relations and protein biosynthesis (Azeem, 2018). These deleterious effects are occasioned by the overproduction of reactive oxygen species (ROS), such as hydrogen peroxide (H 2 O 2 ), superoxide (O 2 − ) and hydroxyl radicals (-OH) (Amari et al, 2017;Yan et al, 2010).…”

“…Phytotoxicity linked to Ni negatively affects photochemical efficiency (Ribeiro et al . 2020), gas exchange (Nazir et al . 2019), water relations and protein biosynthesis (Azeem 2018).…”

“…Phytotoxicity linked to Ni negatively affects photochemical efficiency (Ribeiro et al 2020), gas exchange (Nazir et al 2019), water relations and protein biosynthesis (Azeem 2018). These deleterious effects are caused by overproduction of reactive oxygen species (ROS), such as hydrogen peroxide (H 2 O 2 ), superoxide anion radical (O 2 À ) and the hydroxyl radical (-OH) (Yan et al 2010;Amari et al 2017).…”