To investigate the dehydration effect on the organization of cellulose microfibrils in primary cell walls, we used transmission mode sum-frequency-generation (SFG) vibrational spectroscopy to detect the mesoscale structure of cellulose microfibrils of the abaxial (outer) onion scale epidermis under the never-dried (hydrated with D2O) and the fully air-dried states. Significant changes in the cellulose organization were observed by SFG after dehydration of epidermal walls. In the detection of the hydrated state, epidermal walls exhibited a strong alkyl (CH) stretching peak centered at 2944 cm-1 in SFG spectra, whereas this 2944 cm-1 peak was diminished and a new broad peak at 2920 cm-1 appeared in the fully air-dried state. Further studies on pectate lyase treated onion epidermis with reduced pectin content, and Calcium ions treated epidermis were analyzed by SFG spectroscopy and field-emission scanning electron microscopy (FESEM). Our results proved the collapse of cellulose layers after dehydration. Moreover, it was also confirmed that with the existence of pectin, the dehydration induced shrinkage disrupts or curves the microfibrils within or between each adjacent cellulose lamella.

Probing the dehydration induced changes in the organization of cellulose microfibrils in primary cell walls using Sum-Frequency-Generation (SFG) vibrational spectroscopy

253rd National Meeting (2017)

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