FRACTURE IN POTATO-TUBER PARENCHYMA

Experiments have been carried out to assess the fracture behaviour of potato tuber parenchyma tissue from two different varieties (cvs. King Edward and Record) in three different turgor states (turgid, fresh an d flaccid). Methods included wedge-penetration fracture tests, razor-b lade cutting tests, ball indentation tests and compression tests. Turg or was manipulated by immersion of fresh tissue in osmotica of known c oncentration, and assessed by means of cell pressure probing. No signi ficant differences in properties were ascribed to the difference in va riety. Changes in water status were responsible for appreciable change s in the fracture properties of the tissue. Values of compressive Youn g's modulus and work of fracture were combined to predict critical cra ck lengths for different turgor states under given levels of applied s tress below the yield stress.