The effects of polyethylene terephthalate micro-nanoplastics (PET-MNPs) were tested on the model freshwater species Spirodela polyrhiza (L.) Schleid., with focus on possible particle-induced epigenetic effects (i.e. alteration of DNA methylation status). MNPs (size ∼ 200-300 nm) were produced as water dispersions from PET bottles through repeated cycles of homogenization and used to prepare N-medium at two environmentally relevant concentrations (∼0.05 g L^-1 and ∼0.1 g L^-1 of MNPs). After 10 days of exposure, a reduction in fresh and dry weight was observed in treated plants, even if the average specific growth rate for both frond number and area was not altered. Impaired growth was coupled with a MNP-induced decrease of chlorophyll fluorescence parameters (i.e. ΨET_o and Pi_abs, indicators of photochemical efficiency) and starch concentration, as well as with alterations in plant ionomic profile and oxidative status. The methylation-sensitive amplification polymorphism (MSAP) technique was used to assess possible changes in DNA methylation levels induced by plastic particles. The analysis showed unusual hypermethylation in 5'-CCGG sites that could be implicated in DNA protection from dangerous agents (i.e. reactive oxygen species) or in the formation of new epialleles. This work represents the first evidence of MNP-induced epigenetic modifications in the plant world.

The excessive use of chemical fertilizers and pesticides in agriculture is increasing the demand for novel products to improve the quality of crops in a more sustainable way. Wood distillate (WD, pyroligneous acid) is a by-product obtained during the pyrolysis of plant biomass that can be successfully applied in agriculture due to its ability to enhance the growth, size, and weight of edible plant parts. However, there is little information concerning its plant yield-promoting effects on leguminous crops. The present work investigated the effects of WD on the yield, protein content and mineral composition of chickpea (Cicer arietinum L.), lentil (Lens culinaris L.) and bean (Phaseolus vulgaris L.) plants grown in field conditions. The application of WD showed remarkable yield-promoting effects mostly in lentil plants, which significantly increased plant and shoot biomass, the number and weight of both pods and seeds, as well as the total seed protein content. Furthermore, seeds from WD-treated plants differentially increased the concentration of elements with high nutritional value for human health, including Fe, Ca, Mg and K. These results suggest that the effects of WD among the legumes tested are species-specific and that WD could be an optimal candidate to grow high-yielding legumes with improved seed nutritional quality.

Due to the increasing evidence of widespread sub-micron pollutants in the atmosphere, the impact of airborne nanoparticles is a subject of great relevance. In particular, the smallest particles are considered the most active and dangerous, having a higher surface/volume ratio. Here we tested the effect of iron oxide (Fe₃O₄) nanoparticles (IONPs) with different mean diameter and size distribution on the model plant Tillandsia usneoides. Strands were placed in home-built closed boxes and exposed to levels of airborne IONPs reported for the roadside air, i.e. in the order of 10⁷ - 10⁸ items m^-2. Plant growth and other morpho-physiological parameters were monitored for two weeks, showing that exposure to IONPs significantly reduced the length increment of the treated strands with respect to controls. A dose-dependence of this impairing effect was found only for particles with mean size of a few tens of nanometers. These were also proved to be the most toxic at the highest concentration tested. The IONP-induced hamper in growth was correlated with altered concentration of macro- and micronutrients in the plant, while no significant variation in photosynthetic activity was detected in treated samples. Microscopy investigation showed that IONPs could adhere to the plant surface and were preferentially located on the trichome wings. Our results report, for the first time, evidence of the negative effects of airborne IONP pollution on plant health, thus raising concerns about related environmental risks. Future research should be devoted to other plant species and pollutants to assess the impact of airborne pollution on plants and devise suitable attenuation practices.

The metallicolous populations of the facultative Tl hyperaccumulator Silene latifolia are extraordinarily tolerant and capable of accumulating up to 80,000 μg Tl g ⁻¹ in nature. A growth stimulatory effect of Tl was observed, and this study set out to determine possible mechanisms. Plants from non‐metallicolous and metallicolous populations were subjected to hydroponics dosing experiments at 2.5 and 10 μM Tl. Metal impact on stomatal and non‐stomatal photosynthetic constraints, light energy conversion processes and plant anatomy/ultrastructure was assessed over time. Photosynthetic rates improved in 10 μM Tl‐treated metallicolous plants by 20% compared to controls, partly due to increased stomatal conductance. The latter was mainly driven by Tl‐induced anatomical changes, such as increased central cylinder area and stomatal density, likely to enhance water uptake/translocation and, consequently, leaf metal accumulation. The apparently Tl‐favoured CO ₂ trafficking resulted in ameliorated maximal photosynthetic capacity. The first signs of photosynthetic declines appeared only at very high Tl leaf concentrations (15,000 μg Tl g ⁻¹ ), with limitations involving stomatal and biochemical factors; whereas the photochemical reactions remained functional. The observed Tl‐induced stimulatory response in growth and net photosynthetic rate in metallicolous plants shows that Tl improves physiological performance in Silene latifolia , mainly through improved stomatal conductance.