Membrane–wall attachments in plasmolysed plant cells

Summary.

Field emission scanning electron microscopy of plasmolysed Tradescantia virginiana leaf epidermal cells gave novel insights into the three-dimensional architecture of Hechtian strands, Hechtian reticulum, and the inner surface of the cell wall without the need for extraction. At high magnification, we observed fibres that pin the plasma membrane to the cell wall after plasmolysis. Treatment with cellulase caused these connecting fibres to be lost and the pinned out plasma membrane of the Hechtian reticulum to disintegrate into vesicles with diameters of 100–250 nm. This suggests that the fibres may be cellulose. After 4 h of plasmolysis, a fibrous meshwork that labelled with anti-callose antibodies was observed within the space between the plasmolysed protoplast and the cell wall by field emission scanning electron microscopy. Interestingly, macerase-pectinase treatment resulted in the loss of this meshwork, suggesting that it was stabilised by pectins. We suggest that cellulose microfibrils extending from strands of the Hechtian reticulum and entwining into the cell wall matrix act as anchors for the plasma membrane as it moves away from the wall during plasmolysis.