Determination of inorganic element distribution in the freeze-fixed stem of Al2(SO4)3-treated Hydrangea macrophylla by TOF-SIMS and ICP-AES

To elucidate the effect of soil conditions on the in planta distribution of inorganic elements, an aluminium (Al)-tolerant plant, Hydrangea macrophylla, was cultivated with the addition of Al ion to soils. Freeze-dried stems from the plants were analysed by time-of-flight secondary ion mass spectrometry (dry-TOF-SIMS). Freeze-fixed stems of the plants were analysed by cryo-TOF-SIMS. The inorganic metal content was quantified by inductively coupled plasma atomic absorption spectrometry (ICP-AES). The dry- and cryo-TOF-SIMS mapping analyses showed that in the native sample, inorganic elements are mainly localised in the cortex and pith. Al-treatment [i.e. Al2(SO4)3 administration to the soil] altered the distribution and content of inorganic metals. The actual amount of inorganic elements quantified by ICP-AES showed that Al-treatment on the soil increased the amounts of Na, Mg, Al and Ca and decreased that of K in the stem. The secondary ion counts of inorganic elements in freeze-dried and -fixed samples, determined by dry-/cryo-TOF-SIMS measurements, showed similar variations as that observed with ICP-AES measurements. These results are interpreted as that Al-treatment altered the distribution and amount of inorganic elements in the stems of Al-tolerant H. macrophylla plants.