Analysis of cell arrangements in softwoods using two-dimensional fast Fourier transform

This paper deals with the quantitative analysis method of detecting the periodicities of cell arrangements and cell shapes in transverse sections of softwoods by fast Fourier transform (FFT) image processing. We obtained a strong periodic orientation in the tangential direction and a weak periodic orientation in the oblique direction from the Fourier power spectrum of a dot map representing geometric centers of cells. According to the angular distribution function of the gray level of a Fourier power spectrum image (frequency image), the periodic arrangements among species were compared quantitatively. Then, the cell diameters in the radial and tangential directions could be measured by the Fourier power spectrum, and these were almost the same as the results measured by microscopic methods. The distribution homogeneities of average cell diameters in all directions were evaluated by the frequency distribution function of Fourier power spectrum images. In addition, the angles of the radial and tangential walls were measured with the angular distribution function of the Fourier power spectrum image of a net map that was obtained from the skeletonizing images of cell walls. As an application of the FFT image processing, the variations of the average diameters of the tracheids were measured from the pith to the bark on cross sections of sugi (Cryptomeria japonica D. Don) wood.