SIMS INVESTIGATION OF THE DISTRIBUTION OF K+, NA+, MG2+ AND CA2+ CATIONS IN BIRCH POLLEN

Two microanalytical techniques were used to investigate the inorganic cation content and distributions in birch (Betula verrucosa Ehrh.) pol len. With intact pollen grains, X-ray microanalysis (EDX) could only g ive a mean ionic composition. Secondary ion Microscopy and Spectrometr y (SIMS) appeared to be a more suitable technique to image Ion distrib utions in the different pollen structures. This was carried out with s amples prepared using is new vapour phase technique designed to improv e ion retention. Transmission Electron microscopy (TEM) showed good st ructural presentation of the samples. Monovalent ion (K+, Na+) distrib ution showed features different from those of the divalent cations (Ca 2+, Mg2+). In the vegetative cell, the alkaline cations were mainly di stributed in the most internal part of the cytoplasm and they were pro bably associated with starch grains or concentrated in dry vacuoles. C alcium distribution correlated well with the areas in the cytoplasm of the vegetative cell containing a dense network of mitochondria and en doplasmic reticulum. Within the pollen grain, the sperm cell appeared to contain the most calcium. Calcium was also abundant in the sporoder m. These results reveal the potential of SIMS for pollen studies that include germination, the monitoring of air pollutants and the allergen s-ion interactions.