Mercury (Hg) poses significant risks to human health, the environment, and plant physiology, with its effects influenced by chemical form, concentration, exposure route, and organism vulnerability. This study evaluates the physiological impacts of Hg on Handroanthus impetiginosus (Ip & ecirc; Roxo) seedlings through SPAD index measurements, chlorophyll fluorescence analysis, and Hg quantification in plant tissues. Four-month-old seedlings were exposed for eight days to distilled water containing Hg at 0, 1, 3, 5, and 7 mg L-1. The SPAD index decreased by 28.17% at 3, 5, and 7 mg L-1, indicating reduced photosynthetic capacity. Chlorophyll a fluorescence analysis revealed a 50.58% decline in maximum efficiency (Fv/Fm) and a 58.33% reduction in quantum yield (Phi PSII) at 7 mg L-1, along with an 83.04% increase in non-photochemical quenching (qn), suggesting oxidative stress and PSII damage. Transpiration decreased by 26.7% at 1 mg L-1 and by 55% at 3, 5, and 7 mg L-1, correlating with Hg levels and leaf senescence. Absorption, translocation, bioconcentration, and bioaccumulation factors varied among treatments. Hg accumulated mainly in stems (40.23 mu g g-1), followed by roots (0.77 mu g g-1) and leaves (2.69 mu g g-1), with limited translocation to leaves. These findings highlight Hg's harmful effects on H. impetiginosus, an ecologically and commercially valuable species, addressing a gap in research on its Hg tolerance and phytoremediation potential.

Peanut smut (causal agent Thecaphora frezzii) and seasonal drought are the two main factors reducing peanut yields in Argentina. There are no previous studies about the effect of drought on peanut smut occurrence. We evaluated the effect of soil water limitation on smut symptoms in greenhouse and field assays. Additionally, we analysed the biochemical responses of plants to the combined stress caused by water limitation and smut infection in greenhouse experiments. We found that a moderate water deficit (30% of soil water-holding capacity) increased smut symptoms and differentially increased proline and reduced chlorophylls in the host. Subsequently, we studied the correlation between field precipitation data and smut damage from 2015 to 2020 in naturally infected fields with a high T. frezzii spore load in the soils. Strong correlations between precipitation and severely affected pods, severity disease index and incidence were found from January to March (susceptibility window for T. frezzii infections). We suggest a strategy of irrigation in a specific time frame to mitigate smut damage when there is a water deficit in the growing season.