HYDROGEN-FLUORIDE EFFECTS ON PLASMA-MEMBRANE COMPOSITION, ATPASE ACTIVITY AND CELL STRUCTURE IN NEEDLES OF EASTERN WHITE-PINE (PINUS-STROBUS) SEEDLINGS

Eastern white pine (Pinus strobus L.) seedlings were grown in controll ed environment growth cabinets and fumigated with 0.4 and 1.6 mu g m(- 3) hydrogen fluoride for 2-28 days. Plasma membranes were isolated fro m needles of treated and control seedlings and their chemical composit ion and ATPase activity examined to determine early effects of hydroge n fluoride action. In plants treated for 2 days with both fluoride lev els, ratios of plasma membrane free sterols:phospholipids and sterols: proteins were drastically higher than ratios in control plants. Seedli ngs treated with hydrogen fluoride for 8 days contained plasma membran es with elevated phospholipid:protein and sterol:protein ratios and th eir plasma membrane ATPase activity was higher than that of control pl ants, Prolonged, 28-day hydrogen fluoride treatment with 1.6 mu g m(-3 ) level was the only treatment which produced a drastic inhibition of plasma membrane ATPase activity. During the initial stages of hydrogen fluoride treatment, treated cells did not show alterations of ultrast ructure which were previously shown in cells of plants treated with so il applied sodium fluoride. The results of the present study indicate that the plasma membranes may be among the initial sites of hydrogen f luoride injury to plants as well as initial sites of defense reaction.