Secondary Dormancy
Secondary dormancy occurs in some non-dormant and post dormant seeds that are exposed to conditions that are not favorable for germination, like high temperatures. It is caused by conditions that occur after the seed has been dispersed. The mechanisms of secondary dormancy are not yet fully understood but might involve the loss of sensitivity in receptors in the plasma membrane.
Not all seeds undergo a period of dormancy, many species of plants release their seeds late in the year when the soil temperature is too low for germination or when the environment is dry. If these seeds are collected and sown in an environment that is warm enough, and/or moist enough, they will germinate. Under natural conditions non dormant seeds released late in the growing season wait until spring when the soil temperature rises or in the case of seeds dispersed during dry periods until it rains and there is enough soil moisture.
Seeds that do not germinate because they have fleshy fruits that retard germination are quiescent, not dormant.
Many garden plants have seeds that will germinate readily as soon as they have water and are warm enough, though their wild ancestors had dormancy. These cultivated plants lack seed dormancy because of generations of selective pressure by plant breeders and gardeners that grew and kept plants that lacked dormancy.
Seeds of some mangroves are viviparous and begin to germinate while still attached to the parent; they produce a large, heavy root, which allows the seed to penetrate into the ground when it falls.
Read more about this topic: Seed Dormancy
Famous quotes containing the word secondary:
“Readers are less and less seen as mere non-writers, the subhuman “other” or flawed derivative of the author; the lack of a pen is no longer a shameful mark of secondary status but a positively enabling space, just as within every writer can be seen to lurk, as a repressed but contaminating antithesis, a reader.”
—Terry Eagleton (b. 1943)