Abstract: | Commercially available cell wall-degrading enzymes frequentlyused for protoplast isolation inhibited CO2 fixation and photosyntheticO2 evolution, and stimulated dark respiration by leaf tissueand isolated mesophyll protoplasts of Nicotiana tabacum L. andAntirrhinum majus L. They also depolarized the membrane potentialof cells of leaf tissue, inhibited uptake of 86Rb by tobaccoleaf tissue and isolated mesophyll protoplasts, and stimulated36CI uptake by tobacco leaf tissue. Where studied, these effectswere found to be reversible. The depolarization effect on Antirrhinumleaf cells occurred even when the enzyme preparations had beendenatured, dialysed, or desalted, and the effect was greatestin those fractions of the enzyme preparation which showed thehighest cellulase activity. Plasmolysis of tobacco leaf tissue inhibited photosyntheticO2 evolution, CO2 fixation, and 86Rb uptake to levels belowthose exhibited by isolated protoplasts in media of the samecomposition and osmolarity. The implications of these resultsfor work with leaf tissue and isolated protoplasts are discussed. |