Moisture Effect on Physical Properties of Knotweed (Polygonum cognatum Meissn.) seeds

In this study, the effects of moisture content on some of physical properties (seed dimension, geometric mean diameter, individual seed weight, sphericity, thousand-seed, weight, bulk and true density, porosity angle of repose and static coefficient of friction of knotweed (Polygonum cognatum Meissn.) seeds were investigated. Moisture contents of seeds were 7.95, 13.68 and 19.14% d.b. (dry basis), respectively. The average geometric mean diameter, individual seed weight, sphericity, thousand-seed weight and angle of repose ranged from 1.85 to 1.94 mm, 0.0040 to 0.0046 g, 66.21 to 67.37%, 3.32 to 3.74 g and 18.36 to 25.00 as the moisture content increased from 7.95 to 19.14% d.b., respectively. Bulk density and porosity were decreased from 696.11 to 707.73 kg m -3 , 57.93 to 40.16%, whereas the seed volume, true density and surface area were increased from 3.357 to 3.894 mm 3 , 1654.69 to 1182.64 kg m -3 , and 10.786 to 11.867 mm 2 as the moisture content increased, respectively. The static coefficient of friction on various surfaces (plywood, glass, chipboard and galvanized metal) linearly increased with an increase in moisture content. Since Polygonum cognatum seeds are in small sizes, they can easily be separated at higher moisture contents which will also help sowing of small seed and enhance germination rate.