| Abstrakt: |
Soil contamination by toxic heavy metals (HMs) represents a serious global ecological problem. Among the HMs often verified in agricultural soils, nickel (Ni) excess can cause phytotoxicity, affecting essential anatomical structures and photochemical reactions connected to the photosynthetic apparatus. 24-Epibrassinolide (EBR) is an environmentally friendly plant growth regulator in which this natural steroid can stimulate plant metabolism. The experiment was randomized with four treatments: two nickel concentrations (0 and 400 µM Ni, described as − Ni and + Ni, respectively) and two EBR concentrations (0 and 100 nM EBR, described as − EBR and + EBR, respectively). The objective of this research was to evaluate whether exogenously applied 24-epibrassinolide can mitigate oxidative damage against the photosynthetic apparatus in tomato leaves under excess Ni and to evaluate the leaf structures, stomatal variables, reactive oxygen species (ROS), antioxidant enzymes and nutritional status. The results proved that EBR alleviated Ni stress by protecting the photosynthetic machinery, upregulating the antioxidant system, improving leaf anatomy and favouring stomatal performance. This steroid relieves Ni-induced oxidative stress, stimulating superoxide dismutase (44%), ascorbate peroxidase (46%) and peroxidase (35%), which are enzymes involved in ROS detoxification. In addition, exogenous EBR alleviates oxidative damage against the photosynthetic apparatus, promoting increases in the effective quantum yield of PSII photochemistry (33%), photochemical quenching (20%) and electron transport rate (33%). In parallel, this steroid triggered improvements in leaf anatomy and stomatal performance that resulted in increases in net photosynthetic rate (52%) and water-use efficiency (29%). Simultaneously, the multiple functions of this steroid in the antioxidant system, photosynthetic machinery, gas exchange and anatomical characteristics worked towards the amelioration of nutritional status and to increase the biomass verified in our results. Therefore, this research demonstrated that EBR alleviated the negative interferences caused by Ni stress in tomato plants. [ABSTRACT FROM AUTHOR] |
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