Effect of paclobutrazol on Narcissus tazetta: endogenous cues to improve flowering

Paclobutrazol (pbz) retards plant growth through reducing gibberellin biosynthesis. flowering is critical for narcissus tazetta as a unique cut flower with commercial value. hence, improving its quality and yield is crucial in the cultivation of n. tazetta. this study was carried out to investigate the effect of pbz treatment (25, (50 and 100 mm) on physiological, morphological and anatomical characteristics in n. tazetta. pre-treatment of narcissus bulbs with different pbz levels induced a significant increase in the flowering percent, flower size, scape diameter, phloem and xylem vessels, pith cavity size, leaf thickness, spongy and palisade mesophylls, and vascular bundle width, despite a significant decrease in height and fresh mass of scape at 100 mm. mean germination time of bulbs and flowers significantly increased at 50 and 100 mm pbz while germination index of bulbs showed a significant increase at 25 mm. under pbz treatment, the observed increase in the photosynthetic pigments was followed by high accumulation of sugars. moreover, different concentrations of pbz significantly increased anthocyanin, phenols, proteins, proline, and total antioxidant activity in the narcissus leaves and flowers. no changes in h2o2, malondialdehyde, and activity of catalase and ascorbate peroxidase can be related to no stress-inducing effects of pbz treatment in narcissus. overall, the positive effect of pbz on physiological, morphological, and anatomical function in flowering procedure in n. tazetta offers suggestions of its future usage in other ornamental bulbous plants.