An Investigation into the Effect of Gibberellic Acid and Storage Temperature on Vegetative and Reproductive Characteristics of Tuberose (Polianthes tuberosa)

Tuberose (Polianthes tuberosa L.), from Agavaceae family, is one of the most important cut flowers in tropical and sub tropical areas of the world and has the seventh rate of production between all cut flowers of Iran. In order to investigate different effects of storage temperatures (8 weeks at 4°C, 4 weeks at 4 °C + 4 weeks at 20°C, 8 weeks at 12°C, 4 weeks at 12°C+ 4 weeks at 20°C and 8 week at 20°C) and different concentrations of gibberellic acid (0, 150 and 300 ppm) on quantitative characteristics of tuberose ‘Double’, a factorial experiment was carried out in a Randomized Complete Block Design with three replications. The effects of treatments were investigated on fresh and dry weight, height and number of flower stems, length of spike, speed of germination and flowering, weight and diameter of florets, number and weight of bulbs, and flower longevity. Qualitative and quantitative investigation of growth and flowering indices showed that the highest number of stems was recorded at 20oC storage temperature, which was 20% higher than that at 4oC storage temperature. Stem weight showed a significant correlation with most growth parameters. The most important effect of studied treatments was observed on growth speed. Speed of bulbs germination was affected only by storage temperatures (P < 0.001), while higher GA3 concentration decreased both germination speed (P < 0.05) and flowering speed (P < 0.001). Finally, we suggested that the best treatment was storing bulbs for 4 weeks at 12°C + 4 weeks at 20°C before cultivation and GA3 treatment did not have any significant effects on growth factors of tuberose.