Physiological and molecular study of mechanisms involved in iron and nitrogen nutrition in crops.

The most common adopted agricultural models are still intensive and focalized on the massive use of chemical inputs that comprehends fertilizers which have negative impacts on producers’ economies and, more critically, on the environment. The contribution of plant nutrition field in this context is crucial and needs to be affined to improve the use efficiency of the applied fertilizers and to define new fertilization plans that can also avoid and/or treat properly nutritional disorders of plants. Among the most widespread limiting growth factors are Nitrogen (N), belonging to the macronutrients and Iron (Fe), belonging to the micronutrients. Unbalance availability of these two nutrients can affect plants capacity to cope with both, biotic and abiotic stresses in both monocots and dicots. In order to use fertilizers in a more efficient way and to manage nutrients’ disorders, the focus should be on increasing the nutrient use efficiency and on the fine characterization of interplays between multiple nutritional pathways, especially in limited nutrient condition, where the presence of an element could help the plants to alleviate the deficiency consequences of another one. This thesis focuses on the interplay between Nitrogen and Iron nutritional pathways and especially in the evaluation of the effect of different N-form (Nitrate, Urea or Ammonium) resupplied together with Iron on plants kept in nitrogen and iron deficiency conditions. First with a study of plant responses to different N-form conferred as a solo source or in combination (Nitrate, Urea and Ammonium) in presence of suboptimal Iron nutritional condition. Especially, on one hand, on the composition and translocation of nutrients, amino acids and phytohormones in the xylem sap of Zea Mays plants together with the effects on photosynthesis and transpiration parameters and on the other hand, on the ionomic, metabololomic and gene expression of the early responses of Solanum lycopersicum plants kept in N-deficiency or N- and Fe-deficiency, and then treated with different single N-forms (common for both Fe-nutritional status) and an Fe-resupply (supplied to Fe-deficient plants). Overall, the results reported in this thesis will help clarifying the contribution of each considered N-form on N acquisition in different plant species and moreover will help to better define the early response to the supply of nitrate, urea or ammonium on plants on a multi-omic level and could provide some key points for improving the use efficiency of nitrogen fertilizers. Moreover, it could improve knowledge on the interactions between N and Fe nutritional pathways which poor bioavailability in soils greatly constrains plant productivity.