Every year when I plant my garden, I feel a tinge of doubt. Shaking out lettuce seeds from the packet, they seem hard and lifeless. I drop the seeds into a trench of soil, back fill that with soil, and water well. Then I wonder if they will sprout.
Without fail, tiny seedlings push up from the soil, and in a few short weeks, I am eating salad, my faith in seeds renewed.
As a plant scientist, I know what seeds are made of; in fact, my work focuses on preserving seeds. However, even after decades of growing and preserving seeds, I still feel a sense of delight and wonder at the “fierce energy” of seeds.
Seeds are hard and lifeless in one instance, and then in another, a tomato plant, lettuce or other plant germinates and bursts forth. Soon, they are bursting with flowers, then fruits and vegetables. Truly a miracle, even to a plant scientist.
Seeds have been around for 125 million years, when flowering plants came about in the Cretaceous period. The success of flowering plants depended on protecting, dispersing and ensuring the successful establishment of offspring. Seeds fill those roles, in all their myriad forms, from the microscopic speck of an orchid seed to the 40-pound Coco del Mar palm seed.
The precious plant embryo is protected within a seed coat, which protects the embryo until conditions are right for plant growth. Once germination begins endosperm within the seed provides nutrients for the growing plant.
Some species are so well protected their seeds can endure for years, even hundreds of years in this dormant stage. Although flowering plants are anchored to the ground with roots, their seeds can wander. Different seed shapes, sizes, and fruit-opening mechanisms result in dandelion seeds blowing away on a breeze, okra seeds exploding from pods, cockleburs hitching a ride on socks, and coconuts floating; all moving to new locations where if conditions are favorable, they can germinate and grow.
Seeds have a clever strategy. They will not germinate unless conditions are right for seedling growth. Some species take this even further. Their seeds are dormant. Dormancy keeps the seed quiet, only allowing growth to occur when the right combination of events occur, signaling that conditions are best to ensure the survival of an emerging seedling. This might be a cold moist period, followed by raising temperatures portending spring, or smoke from a fire, foreshadowing nutrient ash and sunshine.
Once the dormancy code is cracked, the seed germinates. The embryo begins to grow, utilizing nutrient tissue within the seed to sustain itself, until the first leaves unfurl and begin to gather energy from the sun. With energy, the plant begins to grow, following the genetic path laid down in DNA, that leads to a fruitful plant. Bury a seed, you get fruit!
Answered by Stephanie Greene, USDA
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