Materials
The silflower seeds (2.37 kg) provided by The Land Institute, Salina, KS were harvested from their research plots just south of the city limits of Salina in 2018 and 2019. The seeds were part of the bulk that included improved plots and new, wild introductions, and intermediate improved x wild populations. The crude harvest from the combine was cleaned using Clipper cleaners of various models (A.T. Ferrell Co. Inc., Bluffton, IN) and various screens to separate seed from chaff and then through an indent cylinder with 16 mm indents (Seed Processing Holland, Enkhuizen, The Netherlands) to remove longer stems and sticks. The seeds were stored in resealable polyethylene bags and stored under ambient conditions until processed.
Measurements of selected physical properties
The bulk seed density was determined by weighing the seeds contained in a 1-liter cup (203 Liter Cup, Seedburo Equipment Co., Chicago, IL). For loose bulk density, the cup was filled with seeds flowing freely from a hopper and then leveled using a straight-edged spatula. The tapped bulk density was measured by shaking and tapping the cup while being filled with seeds and then leveling as described. Seed weight was obtained by weighing 1,000 seeds randomly picked from the bulk sample. The hull and kernel were manually separated from 1,000 seeds. The weights of hulls and kernels were then obtained, and their percentages to the seed weight were calculated. The length, width, and thickness of 20 seeds and kernels were measured using a digital caliper. The true densities of seed, kernel, and hull were obtained by weighing the samples in a 10 cm3 cup, and the true volumes were determined using an AccuPyc II 1340 gas pycnometer, Micromeritics, Norcross, GA. All determinations were performed in triplicate.