Nitrogen nutrition in plants is a key determinant in crop productivity. The availability of nitrogen nutrients in the soil, both inorganic (nitrate and ammonium) and organic (urea and free amino acids), highly differs and influences plant physiology, growth, metabolism, and root morphology. Deciphering this multifaceted scenario is mandatory to improve the agricultural sustainability. In root cells, specific proteins located at the plasma membrane play key roles in the transport and sensing of nitrogen forms. This review outlines the current knowledge regarding the biochemical and physiological aspects behind the uptake of the individual nitrogen forms, their reciprocal interactions, the influences on root system architecture, and the relations with other proteins sustaining fundamental plasma membrane functionalities, such as aquaporins and H⁺-ATPase. This topic is explored starting from the information achieved in the model plant Arabidopsis and moving to crops in agricultural soils. Moreover, the main contributions provided by proteomics are described in order to highlight the goals and pitfalls of this approach and to get new hints for future studies.

In agricultural soils, nitrate (NO₃⁻) is the major nitrogen (N) nutrient for plants, but few studies have analyzed molecular and biochemical responses involved in its acquisition by grapevine roots. In viticulture, considering grafting, NO₃⁻ acquisition is strictly dependent on rootstock. To improve the knowledge about N nutrition in grapevine, this study analyzed biochemical and proteomic changes induced by, NO₃⁻ availability, in a hydroponic system, in the roots of M4, a recently selected grapevine rootstock. The evaluation of biochemical parameters, such as NO₃⁻, sugar and amino acid contents in roots, and the abundance of nitrate reductase, allowed us to define the time course of the metabolic adaptations to NO₃⁻ supply. On the basis of these results, the proteomic analysis was conducted by comparing the root profiles in N-starved plants and after 30 h of NO₃⁻ resupply. The analysis quantified 461 proteins, 26% of which differed in abundance between conditions. Overall, this approach highlighted, together with an increased N assimilatory metabolism, a concomitant rise in the oxidative pentose phosphate pathway and glycolysis, needed to fulfill the redox power and carbon skeleton demands, respectively. Moreover, a wide modulation of protein and amino acid metabolisms and changes of proteins involved in root development were observed. Finally, some results open new questions about the importance of redox-related post-translational modifications and of NO₃⁻ availability in modulating the dialog between root and rhizosphere.

A previous ethnobotanical investigation conducted in Valle Imagna (Northern Italy) highlighted the traditional use of Agrimonia eupatoria L. (Rosaceae) as a disinfectant and wound-healing agent. This use seemed to be linked to a local 18th century manuscript. This species was chosen for a multidisciplinary investigation to validate or refute its traditional use in the valley. Samples from fresh leaves were observed under Scanning Electron and Light Microscopy. The phenolic profiles of an epicuticular aqueous extract of the whole leaves and of infusions and decoctions of leaves and aerial parts were analyzed through Liquid Chromatography–Tandem Mass Spectrometry. The volatile organic compounds (VOCs) of fresh leaves were analyzed through Headspace Solid-Phase Microextraction coupled with Gas Chromatography–Mass Spectrometry. Growth inhibition and adhesion modulation were assessed on Escherichia coli, Staphylococcus aureus, and S. warneri by minimum inhibitory concentration and adhesion assays. Two trichome morphotypes were observed: a capitate with a one-celled rounded head and a capitate with a teo-celled cylindrical head. Both were responsible for producing terpenes, while the cylindrical capitates also produced polyphenols. Thirty-four phenolic compounds were characterized. Luteolin-7-O-glucoside, Catechin, and Epicatechin were common to all five extracts. The VOC profiles highlighted the dominance of (+)-α-Pinene. The infusions and the decoctions had a significant inhibitory activity on E. coli, and the extracts (specifically, the infusion of the leaves and both decoctions) also had a stimulating effect on the biofilm formation of S. warneri. These results already hold particular interest because of the strong connection they have to the traditional use of agrimony described in Valle Imagna.