Climate change will inevitably lead to environmental variations, thus plant drought tolerance will be a determinant factor in the success of plantations and natural forestry recovery. Some metabolites, such as soluble carbohydrates and amino acids, have been described as being the key to both embryogenesis efficiency and abiotic stress response, contributing to phenotypic plasticity and the adaptive capacity of plants. For this reason, our main objectives were to evaluate if the temperature during embryonal mass initiation in radiata pine was critical to the success of somatic embryogenesis, to alter the morphological and ultrastructural organization of embryonal masses at cellular level and to modify the carbohydrate, protein, or amino acid contents. The first SE initiation experiments were carried out at moderate and high temperatures for periods of different durations prior to transfer to the control temperature of 23°C. Cultures initiated at moderate temperatures (30°C, 4 weeks and 40°C, 4 days) showed significantly lower initiation and proliferation rates than those at the control temperature or pulse treatment at high temperatures (50°C, 5 min). No significant differences were observed either for the percentage of embryogenic cell lines that produced somatic embryos, or for the number of somatic embryos per gram of embryonal mass. Based on the results from the first experiments, initiation was carried out at 40°C 4 h; 50°C, 30 min; and a pulse treatment of 60°C, 5 min. No significant differences were found for the initiation or number of established lines or for the maturation of somatic embryos. However, large morphological differences were observed in the mature somatic embryos. At the same time, changes observed at cellular level suggested that strong heat shock treatments may trigger the programmed cell death of embryogenic cells, leading to an early loss of embryogenic potential, and the formation of supernumerary suspensor cells. Finally, among all the differences observed in the metabolic profile, it is worth highlighting the accumulation of tyrosine and isoleucine, both amino acids involved in the synthesis of abiotic stress response-related secondary metabolites.

Atrazine is one of the most used herbicides and has been associated with persistent surface and groundwater contamination, and novel formulations derived from nanotechnology can be a potential solution. We used poly-epsilon caprolactone nano-encapsulation of atrazine (NC+ATZ) to develop a highly effective herbicidal formulation. Detailed structural study of interaction between the formulation and Brassica juncea plants was carried out with evaluation of the foliar uptake of nanoatrazine and structural alterations induced in the leaves. Following postemergent treatment, NC+ATZ adhered to the leaf and penetrated mesophyll tissue mainly through the hydathode regions. NC+ATZ was transported directly through the vascular tissue of the leaves and into the cells where it degraded the chloroplasts resulting in herbicidal activity. Nanocarrier systems, such as the one used in this study, have a great potential for agricultural applications in terms of maintenance of herbicidal activity at low concentrations and a substantial increase in the herbicidal efficacy.

No abstract

Interest in biochemistry of organoselenium compound has increased in the last decades, mainly due to their chemical and biological activities. Here, we investigated the protective effect of diphenyl diselenide (PhSe)2 (5 μmol/kg), in a mouse model of methylmercury (MeHg)-induced brain toxicity. Swiss male mice were divided into four experimental groups: control, (PhSe)2 (5 μmol/kg, subcutaneous administration), MeHg (40 mg/L, in tap water), and MeHg + (PhSe)2. After the treatment (21 days), the animals were killed and the cerebral cortex was analyzed. Electron microscopy indicated an enlarged and fused mitochondria leading to a reduced number of organelles, in the MeHg-exposed mice. Furthermore, cortical creatine kinase activity, a sensitive mitochondrial oxidative stress sensor, was almost abolished by MeHg. Subcutaneous (PhSe)2 co-treatment rescued from MeHg-induced mitochondrial alterations. (PhSe)2 also behaved as an enhancer of mitochondrial biogenesis, by increasing cortical mitochondria content in mouse-receiving (PhSe)2 alone. Mechanistically, (PhSe)2 (1 μM; 24 h) would trigger the cytoprotective Nrf-2 pathway for activating target genes, since astroglial cells exposed to the chalcogen showed increased content of hemeoxygenase type 1, a sensitive marker of the activation of this via. Thus, it is proposed that the (PhSe)2-neuroprotective effect might be linked to its mitoprotective activity.

Aleppo pine (Pinus halepensis Mill.), a native species of the Mediterranean region, has been suggested as a species that when introduced in degraded areas could facilitate the long-term colonization and expansion of late-successional species. Due to climate changes, plants need to withstand extreme environmental conditions through adaptation and changings in developmental pathways. Among other paths, plants undergo changes in developmental pathways controlled by phytohormones. At the same time, somatic embryogenesis has been widely used as a model to understand the mechanisms involved in plant response to different stresses. In this study, in order to induce a strong effect of temperature stress on plants regenerated from somatic embryos, higher temperatures (40 °C for 4 h, 50 °C for 30 min, and 60 °C for 5 min) than the control (23 °C) were applied during the induction stage of somatic embryogenesis in Pinus halepensis. A morphological characterization of the embryogenic cultures showed small differences in the number of starch grains, lipid bodies, and phenolic compounds between treatments. Results showed that high temperatures (60 °C) led to higher rates at the maturation stage of somatic embryogenesis when compared to the control (23 °C), strengthening the productivity through the increase in the number of somatic embryos obtained. Finally, analysis of endogenous concentration of cytokinins showed that different conditions applied during the initiation phase of somatic embryogenesis led to different hormonal profiles; isoprenoid cytokinins showed a clear defined pattern with the higher total hormone concentration being found in embryonal masses induced at 50 °C for 30 min, while different aromatic cytokinins presented different individual responses to the treatments applied. These differences corroborate the idea that cytokinins could be potential regulators of stress–response processes during initial steps of somatic embryogenesis.