Chemical imaging of microstructure of chickpea seed tissue within a cellular dimension using synchrotron infrared microspectroscopy: A preliminary study.

Synchrotron radiation-based infrared microspectroscopy (SR-IMS) is a non-destructive bioanalytical technique with a high signal to noise ratio and high ultra-spatial resolution (3-10µm). It is capable to explore the microstructures of plant tissues in a chemical sense and provide information on the composition, structure, and distribution of chemical compounds/ functional groups. The objective of this study was to illustrate how the SR-IMS can be used to image the internal microstructures of chickpea seed tissue on a cellular level. Chickpea seeds (CDC Cory) were collected from the Crop Development Center (University of Saskatchewan, Saskatoon, SK). The seeds were frozen at -20ºC on the object disks in a cryostatic microtome and then were cut into thin cross sections (ca. 8 μm thick). The experiment was carried out on the Mid-Infrared beamline (01B1-1) at the Canadian Light Source (Saskatoon, SK). We obtained the ultra-spatial images of chickpea tissue with pixel-sized increments of imaging steps. The results showed that with the extremely bright synchrotron light, spectra with high signal to noise ratios can be obtained from area as small as 3.3 µm× 3.3 µm allowing us to observe the seed tissue within a cellular level. Chemical distribution of chickpea such as lipids, protein, and carbohydrates could be mapped, revealing the chemical information of chickpea internal microstructure. In conclusion, SR-IMS can rapidly characterize molecular structure of protein, carbohydrates, and lipids at ultra-spatial resolution.