Seed Size Often Matters

A: Many reasons for a disparity between seed size and plant size have been suggested, and many aspects of plant development are thought to be related to seed size.

Larger seeds are better able to support themselves initially, while smaller seeds have a better chance for dispersal over a wide area, helping some seedlings survive.

Plants also have evolved different adaptations to their sprouting environments, helping some smaller seeds thrive in drier, less nutritious soils, while larger seeds often are able to take advantage of richer soils that hold water better.

Seed size is often related to relative growth speed; smaller seeds develop more quickly than larger ones. But not always: a 2012 study in the journal Ecology concluded that small-seeded species only sometimes possess additional adaptations for rapid growth over and above their general size advantage.

A study last year in the journal PLoS Biology found that a faster evolution of new species in a broad range of plant types is correlated with smaller seed size. Small-seeded plants also tended to have shorter life spans, with the rapid turnover linked to more rapid evolution.