Nodulating white lupins take advantage of the reciprocal interplay between N and P nutritional responses

Peculiarity of the early metabolomic response in tomato after urea, ammonium or nitrate supply

Nitrogen (N) is the nutrient most applied in agriculture as fertilizer (as nitrate, Nit; ammonium, A; and/or urea, U, forms) and its availability strongly constrains the crop growth and yield. To investigate the early response (24 h) of N-deficient tomato plants to these three N forms, a physiological and molecular study was performed. In comparison to N-deficient plants, significant changes in the transcriptional, metabolomic and ionomic profiles were observed. As a probable consequence of N mobility in plants, a wide metabolic modulation occurred in old leaves rather than in young leaves. The metabolic profile of U and A-treated plants was more similar than Nit-treated plant profile, which in turn presented the lowest metabolic modulation with respect to N-deficient condition. Urea and A forms induced some changes at the biosynthesis of secondary metabolites, amino acids and phytohormones. Interestingly, a specific up-regulation by U and down-regulation by A of carbon synthesis occurred in roots. Along with the gene expression, data suggest that the specific N form influences the activation of metabolic pathways for its assimilation (cytosolic GS/AS and/or plastidial GS/GOGAT cycle). Urea induced an up-concentration of Cu and Mn in leaves and Zn in whole plant. This study highlights a metabolic reprogramming depending on the N form applied, and it also provide evidence of a direct relationship between urea nutrition and Zn concentration. The understanding of the metabolic pathways activated by the different N forms represents a milestone in improving the efficiency of urea fertilization in crops.

The Effects of Differentiated Organic Fertilization on Tomato Production and Phenolic Content in Traditional and High-Yielding Varieties

The challenge of sustainable agriculture is to increase yields and obtain higher quality products. Increased antioxidant compounds such as polyphenols in harvest products may be an added value for sustainable agriculture. The aim of the present study was to investigate whether three organic fertilization treatments with different levels of carbon and nitrogen, i.e., N-rich, N-rich+C, and N-poor+C, affected the phenolic content of different tomato varieties. The examined parameters were productivity, plant nutritional status, δ13C, and tomato phenolic content as an indication of the antioxidant capacity. The best production was obtained with ‘Cornabel’, a high-yielding Pebroter variety. The total phenolic content was highest in the traditional ‘Cuban Pepper’ variety regardless of treatment, while naringenin levels were high in all the Pebroter varieties. In N-poor+C fertilized plants, a lower N-NO3 content in leaves was correlated with higher levels of total polyphenols in the fruit. The high-water stress suffered by Montserrat varieties coincided with a low total phenolic content in the tomatoes. In conclusion, organic fertilization with reduced N did not influence the tomato yield but positively affected phenolic compound levels in varieties less sensitive to water stress.