Does integrative effects of glyphosate, gibberellin and hydrogen peroxide ameliorate the deleterious effects of the herbicide on sorghum seed through its germination?

We investigated the interconnected roles of reactive oxygen species (ROS) generated upon seed exposure to glyphosate and/or gibberellic acid (GA3), and the possible interaction between the herbicide and the plant hormone during germination of sorghum seeds. GA3 decreased antioxidant enzyme activity in embryos, and the over accumulation of hydrogen peroxide (H2O2) in 1000 mM GA3-treated seeds resulted in the lowest germinability among treatments. The deleterious effects of glyphosate on germination rate, in contrast, were not related to H2O2 accumulation, but to its interference with the mitochondrial electron transport chain. However, interactions among glyphosate, GA3 and H2O2 during seed germination were observed. Similar to paclobutrazol, glyphosate appears to interfere with the de novo synthesis of gibberellin, which modulates seed germination through oxidative metabolism. Seeds experiencing increased oxidative status due to GA3 (100 mM) or H2O2 (50 mM) applications had the effects of glyphosate on germination rate reversed. Since decreased ATP synthesis is a secondary effect of glyphosate, increased H2O2 concentrations in embryos must facilitate germination by decreasing the energy required by ATP-demanding metabolism. Our results showed that glyphosate affect seed germination of sorghum, and that the herbicide interacts with oxidative and gibberellin metabolisms.

Integrative effects of zinc and temperature on germination in Dimorphandra wilsonii rizz.: Implications of climate changes.

The integrative effects of zinc (Zn; 0 mg L-1 , 75 mg L-1 , 150 mg L-1 , and 200 mg L-1 ) and temperature (25 °C, 30 °C, and 35 °C) on seed germination of the threatened Brazilian species Dimorphandra wilsonii were evaluated. Zinc effects on seed germination were only observed at 30 °C and 35 °C. By stimulating respiration rates, rising temperatures accentuate hydrogen peroxide (H2 O2 ) formation in germinating seeds in the presence of Zn. Seed Zn tolerance was related to the activation of enzymatic antioxidants, and ascorbate peroxidase (APX) activity had a central role in H2 O2 scavenging under the highest temperatures tested. Increased APX activity allowed successful germination, whereas decreasing APX activity was accompanied by decreasing germination rates in Zn-treated seeds at 35 °C. Within a scenario of future climate change, it will be extremely important to avoid increasing Zn concentrations in natural habitats that would threaten conservation efforts directed toward this endangered plant species. Environ Toxicol Chem 2017;36:2036-2042. © 2017 SETAC.