Leaf senescence and petal abscission in flowering plants such asPelargonium occur in the dark during commercial transportation. Both affect plant quality and the commercial viability of the plant. In this experiment, we investigated the effects of 60 mg l-1 silver nanoparticles (SNP) in combination with 75 μM thidiazuron (TDZ) on selected physiological and biochemical characteristics of four cultivars ofPelargonium zonale (‘Foxi’, ‘Flowerfairy’, ‘Bluewonder’, and ‘Anthony’) incubated in the dark. The concentrations of photosynthetic pigments and proteins were measured, and petal abscission and anti-oxidant enzyme activities were analysed under the treatments applied. Following exposure to SNP plus TDZ, the extent of lipid peroxidation as well as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities changed, together with changes in the isozyme patterns of POD and SOD. SNP plus TDZ significantly decreased the incidence of petal abscission and leaf senescence compared to untreated control plants. Photosynthetic pigment concentrations increased in the SNP plus TDZ–treated plants, especially in ‘Anthony’ and ‘Foxi’. A significant reduction in lipid peroxidation was recorded in ‘Bluewonder’ and in ‘Flowerfairy’ flowers following SNP plus TDZ treatment, compared to the untreated controls. APX activities increased in all cultivars, except ‘Foxi’, following SNP plus TDZ treatment compared to the respective untreated control plants. Furthermore, increases in both POD and CAT activities were observed following treatment with SNP plus TDZ. The increases in CAT and SOD activities were most pronounced in ‘Anthony’ and ‘Flowerfairy’, relative to untreated control plants. These results demonstrate that co-treatment with SNP plus TDZ could be an effective strategy to retard post-harvest senescence in sensitive geranium cultivars such as ‘Flowerfairy ‘and ‘Bluewonder’.
