Matsushima, U.; Hilger, A.; Graf, W.; Zabler, S.; Manke, I.; Dawson, M.; Choinka, G.; Herppich, W.B.: Calcium oxalate crystals distribution in rose peduncles: Non-invasive analysis by synchrotron X-ray micro-tomography. Postharvest Biology and Technology 72 (2012), p. 27-34

Comprehensive knowledge of plant microstructures and their variations is essential to understanding the mechanisms underlying postharvest quality changes of horticultural products. In this study, phase-contrast computed microtomography (CT) using synchrotron X-radiation was applied to non-invasively investigate the inner structure of peduncles of samples of three rose cultivars that differ greatly in their shelf life. Due to its high resolution, synchrotron x-ray tomography can be used to study tissues – and even individual cells – without physically interfering with the product. In 3-D CT images of peduncle samples of all cultivars, numbers of small spherical particles with x-ray attenuation much higher than that of cell cytoplasm were observed. These particles were smaller than parenchyma cells and vessel elements, and were mainly scattered in the cortex tissue (but were also present less abundantly between vascular bundles). The X-ray attenuation patterns reflect the high density of these crystalline, biomineral particles. Microscopic evaluation of concomitantly prepared fresh-cut slices clearly indentified these particles as calcium oxalate crystals, which, due to their shape and sizes, can be determined as calcium oxalate druses. To the best of our knowledge, this is the first report on the in-situ distribution of calcium oxalate crystals in rose peduncles.