Celery (Apium graveolens L.) parenchyma cell walls examined by atomic force microscopy: effect of dehydration on cellulose microfibrils

Atomic force microscopy (AFM) was used to image celery (Apium graveolens L. ) parenchyma cell walls in situ. Cellulose microfibrils could clearly be di stinguished in topographic images of the cell wall. The microfibrils of the hydrated walls appeared smaller, more uniformly distributed, and less enme shed than those of dried peels. In material that was kept hydrated at all t imes and imaged under water, the microfibril diameter was mainly in the ran ge 6-25 nm. The cellulose microfibril diameters were highly dependent on th e water content of the specimen. As the water content was decreased, by mix ing ethanol with the bathing solution, the microfibril diameters increased. Upon complete dehydration of the specimen we observed a significant increa se in microfibril diameter. The procedure used to dehydrate the parenchyma cells also influenced the size of cellulose microfibrils with freeze-dried material having larger diameters than air-dried material.