Visualization of morphological structure and water status during storage of Allium aflatunense bulbs by NMR imaging

The effect of cold storage on the developmental morphology and water status in bulb tissues of Allium aflatunense B. Fedtsch. was studied using scanning electron microscopy (SEM) and magnetic resonance imaging (MRI). Morphological MR images were produced by a T₁-weighted spin echo pulse sequence. Water status was assessed according to the ratio between two images acquired at two different echo times (4 and 25 ms) from which an apparent T₂ value was calculated. A significant decrease in T₂ in both vernalized and non-vernalized bulbs was observed after 4 months in storage. This effect may be associated with a reduction in water mobility in stored bulbs. At the end of the storage period, the apparent T₂ values in the basal plate were significantly lower in vernalized than non-vernalized bulbs. Intrabulb floral development was similar in both vernalized and non-vernalized bulbs, but scape elongation and actual bloom occurred only in the vernalized plants. Changes in intrabulb development and water status during storage cannot by themselves provide a valid explanation for the significant differences between vernalized and non-vernalized bulbs during the growth stage. The possible role of the basal plate is discussed.