According to the United Nations report, the world’s population will increase by 2 billion persons in 2050 and so, the challenge for the next thirty years is to double the current rate of food production. In the context of global changes, it is essential to maintain the productivity of agroecosystems to mitigate the increase in atmospheric carbon oxide (CO2) concentrations since photosynthesis is the main entry point for carbon (C) in ecosystems and the availability of mineral nutrients often limits it. Therefore, plant mineral nutrition is a key issue for atmospheric CO2 fixation. On the other hand, the arable land availability decreases due to climate change, and nutrient availability is one of the most serious limitations to crop yields. Unfortunately, nutrient deficiency in food crops often translates into a nutrient deficiency in humans as iron (Fe) deficiency anemia that affects around two billion people globally, according to the World Health Organization. In contrast, the nitrogen (N) pollution level expected by 2050 is projected to be 150% higher than in 2010, with the agricultural sector accounting for 60% of this increase. So, it is therefore urgent to reduce this pollution by finding strategies to increase nitrogen use efficiency. Moreover, it is estimated that around 27% of C allocated to roots is exuded to the rhizosphere through roots. However, this percentage can vary depending on plant species, age, and nutritional status. Thus, root exudates are also important for C sequestration in soils and an important resource for studying how plant metabolism is affected by nutrient deficiencies. In this way, we will gain a better understanding of how to correct these deficiencies with less impact on the environment and in a healthier way for humankind.
Then, ExuNutriStress is an interdisciplinary (plant physiology, analytical chemistry, and bioinformatics) approach to the effects of nutritional deficiencies (N and Fe), individually and combined, on root exudates profiles of poplar trees. The poplar tree (Populus spp) was chosen for this project because it is a fast-growth tree that combines rapid maturation and wide geographic distribution with economic relevance for wood and biomass production and has seldom been studied in terms of nutrition. The main nutrient deficiencies chosen were N and Fe because N is a fundamental macronutrient that takes part in proteins, chlorophyll, nucleic acids, nucleotides, and nucleosides, and its availability is a major determinant of yield. At the same time, iron, among other processes, is involved in photosynthesis, mitochondrial respiration, N assimilation, and hormone biosynthesis, and other plants are already known to use exudates to improve iron availability in soils. Nitrogen and iron deficiencies were tested individually and in combination since plant responses to multiple nutrient stresses are usually not the sum of the plant responses to each stress.
