Effects of exogenous hormones and cold storage on Asiatic lily 'Gironde' × 'Renoir' bulblet growth and development

Asiatic hybrid lily (Lilium) is an excellent cut flower because of its various types and colors. Also, because of its strong cold tolerance, Asiatic hybrid lily is a superior choice to breed new cultivars. A group of bulblets, obtained from hybridizing Lilium Asiatic 'Gironde' and Lilium Asiatic 'Renoir', was treated in vitro with nine different concentrations of exogenous hormone (abscisic acid (ABA), gibberellic acid 3 (GA₃), and 6-benzylaminopurine (6-BA)) solutions, then stored at 4°C for 5 weeks. The effects of exogenous hormone levels and low temperature on further bulb growth were studied. Exogenous ABA could restrain the increase of soluble sugar during the low-temperature treatment, especially when the ABA content reached 0.2 mg L^-1. Meanwhile, the exogenous hormone GA₃ raised the soluble sugar content remarkably. The relative content of carbohydrates is directly related to bulb growth and development after transplanting, thus, we can draw the conclusion that exogenous hormone (GA₃, ABA) treatment could have a significant impact on plant height and leaf number of bulblets after transplanting. Furthermore, a decreasing amount of starch and high accumulation of soluble sugar in outer scales of bulblets were found in the process of dormancy breaking of Asiatic hybrid lily 'Gironde' × 'Renoir'.