The effects of large seed size on plant growth are unanimously positive. Larger seeds produce seedlings that emerge faster, are bigger, and have better access to nutrient sources. For these reasons, "Large seeds favor the survival of seedlings in the face of common stresses such as herbivory, drought or shade," according to a Cambridge Journal abstract based on the writings of Gaëlle Lahoreau and several associates. Seed size studies are and have been conducted on a large variety of plants worldwide with similar results.
Plants with larger seeds emerge faster than those with smaller seeds, according to Katherine L. Gross of Ohio State University. This gives plants with larger seeds an evolutionary advantage over small-seeded plants, because early emergence gives plants speedier access to local nutrient sources. This will stunt or kill small-seeded plants, competing for the same nutrient sources, that emerge slower.
Gross reports that larger seeds create larger seedlings between species and within species of plants. This direct correlation between seed and seedling sizes means that larger seedlings able to withstand common plant dangers are proven to start as larger seeds. Seedling growth and survival is mostly dependent on this ability to withstand danger, and small seeds and seedlings are far more likely to perish from lack of nutrients than larger seedlings.
Increased Nutrient Access
Faster emergence and larger seedlings lead to an increase in nutrient access. "Seedlings from large-seeded species would have better access to light and/or to reliable water supply than seedlings from small-seeded species," states Lahoreau et al. The large seedlings caused from fast emergence provide increased nutrient access to large-seeded plants through increased root sizes and speedier nutrient use. As larger seedlings establish root structures quicker and reach available light faster, small seedlings competing for the same resources will receive partial or none of the nutrients necessary for survival.