AN ALUMINUM-MORIN FLUORESCENCE ASSAY FOR THE VISUALIZATION AND DETERMINATION OF ALUMINUM IN CULTURED-CELLS OF NICOTIANA-TABACUM-L CV BY-2

To determine aluminum (Al) in cultured Nicotiana tabacum L. cv. BY-2 c ells, an in vivo Al-morin fluorescence method was developed, optimized , and validated. A fluorescent reagent for Al-morin was added to cells in an aqueous medium (pH 5.6) and was found to internalize rapidly (< 30 min), presumably via pH-dependent trapping in the cytoplasm. The e xcitation and emission spectra of the Al-morin complex in cells resemb led those in aqueous solution. Given the weak autofluorescence, fluore scence spectra from cells (emission peak about 510 nm, excitation 440 nm), treated with morin alone or with morin and Al, seemed to originat e almost entirely from morin or its complex with Al. Based upon the em ission spectra from cells, the Al-morin complex could be distinguished visually from free morin by intensity and coloration. At higher dye c oncentrations (> 100 mu M) in the incubation medium, fluorescence inte nsity was quenched. Results obtained from the AI-morin method were hig hly correlated (r(2) = 0.94) with those obtained by graphite furnace a tomic absorption spectrometry. The advantages of this dye assay for Al are several fold: it is quick, easy, and inexpensive to perform, and permits measurements and visualization under the microscope, with reso lution comparable to or superior to methods employed hitherto. In addi tion, it is apparently insensitive to precipitated Al. Copyright (C) 1 997 Elsevier Science Ireland Ltd.