Relation of phenolic compounds and nitrogen content of Saffron (Crocus sativus L.) under field conditions

This study was conducted with the aim of evaluating the trend of changes in phenolics and nitrogen contents in aerial, underground and rhizosphere of saffron based on a randomized complete block design with four replications during two years of 2008 and 2009. Four samplings were performed as follows: rhizosphere, corm and leaves were sampled in early Oct., early Feb., 2009, and early May, early July, 2010 from four- year old farms in central section of Abrood village in Torbat-e-Heidarieh city. In order to measure total phenolics and nitrogen contents Folin Cio-Calteau micro method and micro-kjeldahl methods were applied, respectively. Results showed that nitrogen and phenolic contents of saffron aerial and underground organs and rhizosphere were significantly different during sampling stages (p≤0.05). Nitrogen and phenolic contents of leaves were much higher than corm and rhizosphere. So the highest phenolic contents in the first, second, third and fourth sampling stages were recorded for corm, leaf, leaf and rhizosphere with 3.13, 7.47, 11.48 and 0.28 mg.kg-1, respectively. The maximum nitrogen contents in these stages were observed for corm, leaf, leaf and rhizosphere with 1.60, 2.29, 1.14 and 0.91 mg.kg, respectively. By increasing nitrogen content, phenolic increased linearly, so that correlation coefficient of nitrogen and phenolic contents were determined equal to r2=0.92**. Increase of nitrogen use affected by increase of carbon allocation due to increasing photosynthate production caused to increase phenolic concentrations as one of the most important secondary metabolites.