Variations and Correlations between the Physical Properties of Seeds of Eleven Spruce Species

Information about the variations and correlations between the physical properties of seeds is essential for designing and modeling seed processing operations. The aim of this study was to determine the variations in the basic physical properties of seeds of selected spruce species and to identify the correlations between these attributes for the needs of the seed sorting processes. Terminal velocity, thickness, width, length, mass and the angle of external friction were determined in the seeds of 11 spruce species. The measured parameters were used to calculate three aspect ratios, geometric mean diameter, sphericity index and specific mass of each seed. The average values of the basic physical properties of the analyzed seeds were determined in the following range: terminal velocity – 5.25 to 8.34 m s-1, thickness – 1.10 to 2.32 mm, width – 1.43 to 3.19 mm, length – 2.76 to 5.52 mm, the angle of external friction – 23.1 to 30.0°, and mass – 2.29 to 18.57 mg. The seeds of Jezo spruce and Meyer's spruce were most similar to the seeds of other spruce species, whereas oriental spruce seeds differed most considerably from the remaining seeds. Our findings indicate that spruce seeds should be sorted primarily with the use of mesh sieves with longitudinal openings to obtain fractions with similar seed mass and to promote even germination.