The researchers studied how different planting densities affect the seed yield of a three line hybrid cotton. They found that the best planting density for high seed yield is between 37,500 and 45,000 plants per hectare. At this density, the cotton plants had higher leaf photosynthetic rates, more bolls per plant, more fruit branches per plant, and heavier bolls. This led to seed yields of 3,922.5-4,027.5 kg per hectare.