Effect of different inorganic nitrogen supplementation on proline and its metabolism enzymes in two Moroccan Sorghum ecotypes

In order to better understand the biochemical mechanisms of proline metabolism under different nitrogen (N) level and source treatments in sorghum plants, different biochemical parameters on shoots and roots of two Moroccan sorghum Ecotype (3P4 and 4P11) such as photosynthetic pigments content, protein content, amino acid content, proline content and two proline metabolizing enzymes were investigated. Proline content reached its highest value under N deficiency and ammonium excess. Furthermore, the proline degradation enzyme (ProDH) activity was lower under N deficiency and ammonium excess. The proline dehydrogenase activity was inversely proportional to the proline content and to the proline biosynthesis enzyme (P5CS) activity which explains the proline accumulation under N stress. We showed also that 4P11 has higher photosynthetic pigment, amino acid and protein contents with less proline accumulation which may indicate a higher tolerance to N stress for this ecotype compared to the 3P4. Therefore, the biochemical analysis reported here may be used for the selection of genotypes with higher tolerance to N stress.