Nitric oxide delays flower senescence in Cosmos sulphureus Cav. by improving antioxidant mechanisms and regulating nutritional dynamics

Senescence marks the final phase in flower development involving a sequence of irreversible events that inevitably lead to death of the petals. The process is regulated by a coordinated interplay between different phytohormones, orchestrating various physiological and biochemical pathways in flowers. Nitric oxide (NO) is an unconventional growth regulator and novel signaling molecule, regulating various physiological processes in plants. We investigate the role of sodium nitroprusside (SNP), a NO donor, in regulating the postharvest senescence of isolated flowers of Cosmos sulphureus. Four sets of harvested flower buds were treated with different grades of SNP, viz, 50, 100, 150, and 200 μM, each with ten replicates. Another set of flowers in distilled water (DW) served as the control. Our results indicated that 150 μM SNP significantly delayed flower senescence in Cosmos sulphureus. Delayed flower senescence was associated with an improved membrane stability index (MSI), accentuated superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity, and also alleviated hydrogen peroxide (H2O2) levels in petal tissues. Furthermore, SNP preserved higher levels of total phenols, sugar fractions, and soluble proteins while inhibiting bacterial growth in test solutions, correlating with increased solution uptake. The observed augmentation in soluble protein content corresponded with reduced specific protease activity (SPA) and α-amino acid content. SNP delayed flower senescence principally by fortifying the antioxidant machinery and preserving the nutritional status of petals.