Membrane deletion during plasmolysis in hardened and non‐hardened plant cells

Video recordings of interference phase contrast microscopy were used to study plasmalemma deletion during plasmolysis in hardened and non‐hardened suspension cultured cells of Brassica napus , alfalfa, and cells isolated from rye seedlings. Although different hardening regimes and different cells were used, the responses to plasmolysis were consistent. Hardened cells uncoupled the volume to surface area ratio during plasmolysis both by forming a large number of strands between the cell wall and protoplast and by leaving rivulet‐like networks of membranes on the cell wall surface. Tonoplast membrane was deleted as sac‐like intrusions into the vacuole. Non‐hardened cells produced few strands during plasmolysis. They also deleted plasmalemma and tonoplast into the vacuole as endocytotic vesicles. During deplasmolysis of hardened cells both the individual membrane strands and the rivulets of membrane material vesiculated into strings of vesicles. The vesicles were osmotically active and were re‐incorporated into the expanding protoplast. Conversely, deplasmolysis in non‐hardened cells resulted in few osmotically active vesicles and many broken strands. The vacuolar sac‐like intrusions in hardened cells were re‐incorporated into the vacuole whereas the endocytotic vesicles in non‐hardened cells were not re‐incorporated. Therefore, the non‐hardened cells underwent expansion‐induced lysis.