Accumulation Sites of A1 in Snapbean and Cotton Roots1

Abstract

AbstractAluminum toxicity is an important growth‐limiting factor in many acid soils. The exact site of A1 injury within roots is unknown. The objective of this study was to determine the site of A1 injury within roots of snapbeans (Phaseolus vulgaris L., ‘Dade’ and ‘Romano’) and cotton (Gossypium hirsutum L., ‘Hancock’) treated for 12 days with 20 mg/liter A1 in nutrient solution at pH 4.6. Location of A1 and other elements in roots was determined by X‐ray microanalysis on a scanning electron microscope. Linear scans across root sections revealed that A1 and P coprecipitate on or in the outer cells of the root cap. The major elements detected in spot analysis of nuclei, cytoplasm, and cell walls were A1, P, S, and Ca. Comparison of analyses on the three main cell structures revealed that the greatest concentration of A1 was in the nucleus. Within the cells, A1 probably accumulates by ionic exchange onto esteric P in the nucleic acids and membrane lipids. In the nuclei, A1 probabily reduces or inhibits cell division by interference with nucleic acid replication.