A new study published in the journal Trends in Ecology & Evolution examined the various strategies through which plants disperse their seeds. By investigating the intricacies of the chemical ecology of seed dispersal, a research team led by Virginia Tech aims to clarify how chemicals impact the interaction between fruit and the animals that eat them.
“Our understanding of the chemical ecology of seed dispersal is still pretty basic. A lot of the chemicals in fruits haven’t yet been described, and we know very little about the functions that these chemicals may have,” said study lead author Annika Nelson.
Just like humans and other animals, plants seem to want their offspring to be successful once they leave the “nest.” In order to have the highest chances of success, seeds need to be planted far away from their parents to minimize competition for nutrients, water, or light. Yet, since plants are rooted in the ground, they have to get creative for their dispersal strategies.
While plants like the Virginia stickseed make their seeds sticky so they cling to passers-by, and maple trees have created winged-seeds that can glide with the wind, most plants enlist the help of animals. By enclosing their seeds in appealing, delicious fruit, plants attract animals who eat the fruits and defecate them in different locations.
The chemicals plants use to lure potential seed dispensers are called secondary metabolites and give fruit their distinctive color and flavor. Since timing is crucial for proper seed dispersion, these metabolites notify animals when it is the right time for them to harvest the fruits.
“Ripe fruits are often a lot smellier and tastier than unripe fruits on purpose,” explained Nelson. “It communicates to animals when fruits are ready to be removed. If seeds are removed from a plant before they are fully developed, they often won’t survive.”
Sometimes, secondary metabolites can also have repelling effects, in order to prevent animals from destroying the seeds or to defend them from various viruses or bacteria. Plants must continuously strike a careful balance between attracting animals to distribute their seeds and fending off predators.
“Because the same metabolites can serve multiple functions across different seed dispersal stages, with the potential for complex trade-offs, examining their effects under multiple contexts is necessary to understand their adaptive significance,” the authors concluded.