24-Epibrassinolide induces protection against nickel excess in soybean plants

Abstract

Soybean [Glycine max (L.) Merrill] is a legume of great socioeconomic relevance, both nationally and internationally. The excess of Ni can seriously affect germination, plant growth, and impair enzyme activity. EBRs are introduced as a new group of plant steroid hormones that act in stimulating a wide range of physiological reactions in the plant, including cellular and metabolic functions. Our objective was to reveal the structural, physiological, biochemical, nutritional, and growth behavior of soybean plants subjected to stress by a high dose of Ni and to identify the possible benefits caused by EBR. The experiment was randomized with four treatments, including two concentrations of Ni (0 and 200 μM Ni, described as - Ni2 + and + Ni2 +, respectively) and two concentrations of 24-epibrassinolide (0 and 100 nM EBR, described as - EBR and + EBR, respectively. The excess of Ni2 + caused damage to the root and leaf structures, resulting in anatomical changes in these tissues. In the roots, the EBR increased the thickness of the epidermis (27%), protecting the root from the Ni2 + ion. In relation to the leaf tissue, significant increases in palisade parenchyma thickness (11%) and spongy parenchyma (29%) were observed. Plants submitted to EBR-treatment under Ni stress showed increases by 50%, 27%, 40%, and 19% in antioxidant enzymes such as SOD, CAT, APX, and POX, respectively, promoting significant reductions in O2-, H2O2, MDA, and EL by 20%, 5%, 9%, and 10%, respectively, when compared with the Ni2+ - treatment at 0 nM of EBR Our results confirm that pretreatment with 100 nM of EBR clearly reduced the anatomical disturbances caused by the excess of Ni in the structures of the leaves and roots, with positive performance, also attenuating the high content of nickel in the nutritional, physiological, biochemical and growth characteristics in the soybean crop.