Amino acid metabolism and expression of genes involved in nitrogen assimilation in common oranges cv. Valencia Late

Numerous studies have been conducted to evaluate the impact of organic and conventional production systems on nutrients, antioxidant substances, and N-containing components in fruits and vegetables (Brandt and Molgaard 2001, Carbonaro and Mattera 2001, Rapisarda et al. 2005 and 2010, Del Amor et al. 2008, Esch et al. 2010, Rosen 2010, Camin et al. 2011, Chebrolu et al. 2012). Ecological and agronomic studies on the influence of fertilization on plant metabolism have shown that there is an inverse relationship in plants between the available N and the accumulation of defence-related secondary metabolites such as vitamin C (Brandt et al. 2011). It has been shown that changes in N status play an important role in the secondary metabolism of plants, in which nitrogen deficiency leads to a marked shift from the N-containing compounds to the production of carbon-rich defencerelated phenylpropanoids (Leser and Treutter 2005, Toor et al. 2006, Benbrook et al. 2008, Nguyen and Niemeyer