In summary, a seed must find its safe site, i.e. a site that provides all the conditions necessary for the seed to germinate and emerge from the soil. These conditions include the environmental conditions necessary to break dormancy and allow germination to proceed, as well as protecting the seed and seedling from hazards such as herbivores, competitors and disease. The problem is that most seeds do not end up in a safe site. A seed is not guaranteed to find a safe site because it cannot control its own dispersal; dispersal agents like animals, wind and water do not guarantee safe passage and delivery to a good place to germinate and grow.
Even if the seed finds a safe site and then germinates, the seedling may not survive because safe germination sites may not promote seedling emergence. A seedling may require different environmental conditions, or the environmental conditions may change by the time a seedling emerges.
Environmental conditions are the main barrier to finding a safe site. The environmental conditions needed for a safe site vary among individuals, populations and species. In response to different selection pressures wrought by environmental variation, plants have adapted. Adaptations include increasing the number of seeds produced, increasing the resources allocated to seeds (parents 'pack a bigger lunch' in bigger seeds to sustain them), having protective seed coats, and using dormancy to wait in the seed bank until a safe site is available. Once a safe site is available, a seed may germinate and produce a seedling. In the next chapter, we will discuss how plants respond to the challenges of life as they grow up.
Was this article helpful?