158 Dormancy of Ornithogalum Evaluated by Nuclear Magnetic Resonance Imaging

Ornithogalum hybrid bulbs (selection 327-2) were stored dry at 10, 16, 22, 28, and 35 °C for 6 weeks upon harvest. After storage, bulbs were subjected to a nuclear magnetic resonance (NMR) imaging to obtain the longitudinal spin-lattice relaxation time (T1) profile across the cross section of intact bulbs and to a scanning electron microscopy (SEM) to observe an inflorescence development. Bulbs were forced in a greenhouse maintained at 21/19 °C. When bulbs were stored at 10, T1 was shorter through the cross section of bulbs and the shoot apex was under a vegetative stage. This suggests that dormancy was not broken during the storage, leaf emergence was delayed, and plants failed to flower. Bulbs stored at 22 and 28 °C formed the primary scape and inflorescence with several florets. At the base of the primary scape of bulbs stored at 22 °C, a vegetative apex was observed by both MR imaging (MRI) and SEM. In the center of bulbs where leaves and floral organs were present, T1 was longer as compared to the scales. This suggests that dormancy in the scales was broken and the leaves and scape were ready to emerge. Leaf emergence and flowering was the fastest when bulbs were stored at 22 °C and at 16 or 22 °C, respectively. Due to its nondestructive nature, MRI can be used to study the state of bulb dormancy and also the progress of inflorescence development during bulb storage prior to planting.