Gibberellin and cytokinins modulate flower senescence and longevity in Nicotiana plumbaginifolia

The efficacy of various growth regulators viz. gibberellic acid (GA₃), kinetin (KIN) and benzylamino purine (BAP) in delaying senescence and improving longevity of excised flowers in Nicotiana plumbaginifolia Viv. was examined. Excised buds of N. plumbaginifolia were harvested one day before anthesis, cut to a uniform pedicel length of 3 cm, and divided into different sets, each set comprising of 25 vials with 5 mL of the respective test solutions. Each set was supplied with various concentrations of GA₃, BAP or KIN viz., 25, 50, 75, 100, 125, and 150 mg L^‑1. A separate set of flowers held in distilled water (DW) was designated as control. The growth regulators used during the present study resulted in significant enhancement of flower longevity as compared to the control. The exogenous application of KIN in the solution was found to be quite effective in improving the flower longevity by an increment of 4.2 days as compared to BAP or GA₃, in which the increment of improvement was 3.9 or 3.5 days, respectively, compared to the control (which lasted for only 3 days). Increased flower longevity by the application of GA₃, BAP or KIN was associated with decreased lipid peroxidase and lipoxygenase (LOX) activities, and increased activities of various antioxidative enzymes viz., catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX). Higher values of soluble proteins, sugar fractions, total phenols and membrane stability index were maintained in the petal tissues from flowers held in the various growth regulators.