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 ou t the quantitative imaging of boron in hypocotyl sections of flax seed lings. At the tissue level, the mean boron concentrations (mmol kg(-1) , dry weight) are highest in the phloem (almost 18), lowest in those t issues 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 oth er tissues (epidermis, cortical parenchyma and medullar parenchyma). B oron concentrations (mmol kg(-1), dry weight) were also determined in subcellular compartments: 13.4 and 15:6 in the cell vacuoles of the co rtical parenchyma and the fibres, and 1.1 in the secondary wall of the fibres. Combining these subcellular data with the data obtained at th e tissue level, we were able to carry out a rough evaluation of the bo ron concentrations (mmol kg(-1), dry weight) in the primary wall of ce lls in different tissues (8 for epidermis and medullar parenchyma, 16 for cortical parenchyma, 28 for phloem, 43 for xylem and 80 for the di fferentiated fibres).