Recent studies have indicated that separation of cottonseed (Gossypium hirsutum L.) for improvement in seed quality should be based on seed density rather than seed size or weight. Seed density is closely related to embryo maturity and is more independent of genotype than are other seed properties. The primary objective of this study was to determine the effect of seed density on some of the processes associated with cottonseed germination and seedling establishment of several cultivars. Acid delinted seed were separated into four density groups using a pneumatic separator. Rate of imbibition, quantity and quality of material leached from the seed, rate of radicle elongation, germination and seedling emergence percentages were measured as indicators of seed quality and seedling vigor potential. Germination percentages were directly related to both seed density and seed weight, with the better correlation existing with seed density. The rates of imbibition and radicle elongation were related to seed density within a cultivar with differences existing between cultivars. A slower rate of radicle elongation was observed for the highest density class during the first 2 to 3 days of germination, which was related to a decreased rate of imbibition during the first 8 hours of contact with water. The quantity of soluble sugars, Ca, and K leached from the seed during imbibition was inversely related to seed density, suggesting interferences existed during seed development or deterioration had occurred in the low density seed. Seed density was highly related to rate of emergence, total emergence, and seedling survival under both growth chamber and field conditions. The results obtained suggest that seed density is the best predictor of cottonseed germination, emergence and potential seedling vigor. Seed separation for improvement in seed quality should be based on density rather than other seed properties.

Recent studies have indicated that cottonseed (Gossypium hirsutum L.) germination and seedling vigor are more closely related to seed density than to any other physical properties such as size or weight. This study was undertaken to determine the physical and chemical differences among seed of different densities within a cultivar and among seed of the same density between cultivars. The primary objective was to relate physical or chemical properties to seed density and to offer an explanation for the reported correlation between seed density, germination, and seedling vigor. Cottonseed of 10 cultivars grown on the Texas High Plains were separated into 4 density groups using a pneumatic separator and increasing air velocities. Separation of seed by density was somewhat independent of cultivar; whereas, seed weight was highly dependent on the cultivar. As seed density increased, the proportion of the total seed weight attributable to the embryo increased from 50% to 65% across all cultivars. The lipid concentration increased significantly from the lowest to the second density group, then remained essentially constant thereafter. All chemical constituents increased significantly when expressed on the basis of seed content. A significant cultivar effect existed within each density group with respect to the quantity of material present. Seed density was a good indication of seed maturity, as shown by the ratios of embryo weight to total seed weight. Although the concentrations of the various chemical constituents were only slightly affected, the quantity of both organic and inorganic material available to the germinating seedling was increased as seed density increased.