Influence of the anisotropy of plant tissue and the orientation of applied electric fields on electropermeabilization
2009
Chalermchat, Y.
The phenomenon called electropermeabilization of cell membranes has been known for several decades and has recently received increasing attention for the manipulation of cells and tissues. The influence of the anisotropy of plant tissue and the orientation of applied electric fields on electropermeabilization was investigated. Apple parenchyma was selected as a model tissue since it contained a high degree of cell size distribution. Different tissue regions were viewed under the microscope to study cell size, shape and orientation. In a parallel experiment, cylindrical samples of tissue were subjected to pulsed electric fields an the change in electrical resistance was measured by the voltage-current method. The measured electrical resistance during pulsing was then converted into a permeability index which defined the relative change in electrical resistance compared to the electrical resistance of frozen/thawed tissue that served as a reference of completely damaged tissue. Electrical impedance was also measured to monitor the tissue changes as affected by pulsed electric fields. The results showed that elongated cells taken from to the inner region of the apple parenchyma, responded to the electric fields in different ways. Fields of lower intensity were required to permeabilize these cells when the fields were applied parallel to the longest axis of the cells. Other field orientations resulted in greater applied electric fields being required to permeabilize the cells. No fields orientation dependence was observed for round cells that belonged to the other region of the apple parenchyma. A condition in which a high degree of permeabilization during pulsing and very small change after pulsing were observed could be obtained at a low applied field of intensity of about b200 V/cm.
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