Exogenous Application of the Polyamine Spermine Delays Natural Leaf Senescence in Wheat Through Protecting Chlorophyll from Degradation and Preventing Oxidative Stress

Senescence is a genetically regulated process that involves decomposition of cellular structures and the mobilization of the products to other plant parts. The progression of developmental senescence in wheat plant under the effect of foliar application with 100 µM of the polyamine spermine (Spm) was studied. Biochemical changes were recorded in the fourth leaf starting from the onset of senescence at 30 day after sowing (DAS) until the end of leaf senescence at 50 DAS. Leaf senescence was delayed in Spm-treated plants through maintaining water content, preventing chlorophyll degradation and enhancement of total soluble sugars, starch accumulation and total protein compared to controls. In addition, reactive oxygen species and lipid peroxidation were lower in Spm-treated plants than control values. Catalase (CAT) activity was obviously lowered due to Spm-treatment; however, guaiacol peroxidase activity was slightly decreased below the control