Developmental changes and water status in tulip bulbs during storage: visualization by NMR imaging

Magnetic Resonance Imaging (MRI) and light and scanning electron microscopy (SEM) were used to follow time-dependent morphological changes and changes in water status of tulip bulbs (Tulipa gesneriana L., cv. 'Apeldoorn') dur ing bulb storage for 12 weeks at 20 degrees C (non-chilled) or 4 degrees C (chilled) and after planting. MR images reflecting the water content, the r elaxation times T-1 and T-2(or their reciprocal values, the relaxation rate s R-1 and R-2), and the apparent self-diffusion coefficient of water molecu les (ADC), were obtained for intact bulbs. After planting, scape elongation and flowering occurred only in chilled bulbs, while elongation in non-chil led bulbs was retarded, Microscopic observations showed different structura l components and high heterogeneity of the bulb tissues, MRI revealed the e longation of the flower bud during storage, which was significantly faster in the chilled bulbs. In addition, MRI demonstrated a redistribution of wat er between different bulb organs, as well as significant differences in the pattern of this redistribution between the chilled and non-chilled bulbs. Generally, R-2 relaxation rates became faster in all bulb organs during sto rage. At the same time, ADC values remained constant in the chilled bulbs, while exhibiting a significant increase in the non-chilled bulbs.