Temperature effects on Zn-responses and Zn-reclamation capacity of two native Brazilian plant species: Implications of climate change

Climate changes implications on the physiological responses and Zn-reclamation capacity of two native Brazilian plant species [Albizia polycephala and Pterogyne nitens (Fabaceae)] were studied. Plants were grown in substrate amended with 0 and 200 mg kg−1, under increasing temperatures (25 °C, 30 °C and 35 °C) and plant physiological responses related to energetic and oxidative metabolism and Zn-uptake and subcellular localization were evaluated. By impairing the mitochondrial metabolism, Zn was seen to induce hydrogen peroxide (H2O2) production, which was stimulated by increasing temperature. However, increasing temperature was also seen to stimulate the activity of antioxidant enzymes, attenuating oxidative damage induced by H2O2 in leaves and roots. Moreover, increasing temperature was responsible for changes in the subcellular localization of Zn, increasing its allocation in the soluble fraction (mainly composed of vacuoles and cytoplasm) - which could be a tolerance mechanism allowing plants to survive in conditions of toxic levels of Zn under increased temperatures. Our results point to an interactive effect of rising temperature on Zn toxicity to plants. Although rising temperatures led to increased uptake of Zn and increased its deleterious effects to mitochondria metabolism (which led to increased H2O2 production), the increases in temperature also promoted the activity of antioxidant enzymes, responsible for H2O2 scavenging, thus attenuating the deleterious effects of this ROS on the cell metabolism of plants. Finally, increases in temperature do not constrain the ability of A. polycephala and P. nites to reclaim Zn and, therefore, these species should continue to be used in Zn-phytoremediation programs even given the prospects of increasing temperatures over the next century due to climatic changes.