QUANTITATIVE IMAGING OF THE DISTRIBUTION OF BORON IN HYPOCOTYL SECTIONS OF FLAX SEEDLINGS, USING NEUTRON-CAPTURE RADIOGRAPHY

We have used the method of ''neutron capture radiography'' to carry out the quantitative imaging of boron in hypocotyl sections of flax seedlings. At the tissue level, the mean boron concentrations (mmol kg(-1), dry weight) are highest in the phloem (almost 18), lowest in those tissues made up of cells with secondary walls (4.1 in the xylem and 2.8 in the differentiated fibres), and in the range of 9 to 13 in the other tissues (epidermis, cortical parenchyma and medullar parenchyma). Boron concentrations (mmol kg(-1), dry weight) were also determined in subcellular compartments: 13.4 and 15:6 in the cell vacuoles of the cortical parenchyma and the fibres, and 1.1 in the secondary wall of the fibres. Combining these subcellular data with the data obtained at the tissue level, we were able to carry out a rough evaluation of the boron concentrations (mmol kg(-1), dry weight) in the primary wall of cells in different tissues (8 for epidermis and medullar parenchyma, 16 for cortical parenchyma, 28 for phloem, 43 for xylem and 80 for the differentiated fibres).