**Acknowledgements**

NBT staining indicated an increased amount of O2

238 Abiotic and Biotic Stress in Plants - Recent Advances and Future Perspectives

relative to control (Figure 5b) [84].

oxidative stress [84].

Superoxide (O2

−

**10. Final considerations**

nutritional exigency of the plant.

plate of the Cu-stressed seedlings compared with the non-treated control (Figure 5a). Similarly, DAB staining confirmed a marked increase in brown polymerization products, which indicated the over-accumulation of H2O2 in the leaves of the Cu-stressed seedlings

Results described by Mostofa et al. [84] indicate that prolonged exposure to excessive Cu resulted in serious toxic effects on the rice seedlings. In contrast, Tre pretreatment has been shown to be beneficial in alleviating Cu toxicity, which was mainly attributed to the ability of Tre (i) to restrict Cu uptake and accumulation to maintain Cu homeostasis, and (ii) to induce production of antioxidant and Gly enzymes to alleviate excessive Cu-triggered

**Figure 5.** Effect of exogenous trehalose on ROS accumulation in leaves of rice seedlings with or without Cu stress. (a)

um (NBT) solution and 3,3'-diaminobenzidine (DAB), respectively, at day 7 of Cu stress. Control, Tre, Cu, and Tre + Cu correspond to control, 10 mM trehalose, 100 μM CuSO4, and 10 mM trehalose + 100 μM CuSO4, respectively [84].

Micronutrient elements such as zinc, boron copper, iron, manganese, molybdenum, and chlorine are responsible to the regulatory activity of the cell organelles. These nutrients are absorbed and found in lower concentrations in plant tissues, and contribute to supply the

Study with *Zea mays* plants exposed to Zn toxicity + Si presented more significant increases in stomatal conductance, net photosynthetic rate, transpiration rate, and water use efficiency

) and (b) Hydrogen Peroxide (H2O2) production in rice leaves were detected using nitro-blue tetrazoli‐

– as scattered dark blue spots in the leaf

This chapter had financial support from Fundação Amazônia Paraense de Amparo à Pesquisa (FAPESPA/Brazil), Universidade Federal Rural da Amazônia (UFRA/Brazil) and Conselho Nacional de Pesquisa (CNPq/Brazil) to Lobato AKS.
