The Use of Ethanolamine in the Study of Pollen Wall Stratification

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Abstract
Confusion over the proper nomenclature and differential effectiveness of ethanolamine and several closely related organic solvents has led to some ambiguity in the use of these compounds in the study of pollen wall stratification. Ethanolamine, diethanolamine and triethanolamine are internationally accepted synonyms for 2-aminoethanol (H2NCH2CH2OH), 2,2′-dihydroxydiethylamine (NH(CH2CH2OH)2), and 2,2′,2″-trihydroxytriethylamine ((HOCH2CH2)3N), respectively, and it is suggested that these simple synonyms be used in palynological investigations. Ethanolamine and diethanolamine are demonstrated to be the most effective solvents for selectively removing the outer ektexine of angiosperm pollen walls without destroying the inner endexine layer. In addition, fixation techniques and age of pollen samples are shown to affect the reactivity of the exine to each solvent in both dicotyledon (Passiflora, Ipomoea) and monocotyledon (Gladiolus) pollen. Conflicts between ontogenetic and chemical criteria for recognizing the presence of endexine suggest that cytochemical tests should be used in conjunction with, or in preference to, developmental evidence for stratified nexines.