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The main causes of seed dormancy are:

  1. It may be due to the impermeability of seed coat which will prevent the absorption of water and gases. So the embryo fails to grow because of the physiological limitations. That is the in availability of water and oxygen.
  2. The seed coats of certain plants are with high mechanical resistance so the seedlings cannot come out through the seed coat. That is it mechanically limits the growth of the embryo.
  3. In certain seed the completed development of the takes place only after the shedding. So the seed germination takes place only after completing the seed development as in the Ginkgo.
  4. The presence of certain inhibitory substances in the endosperm, embryo or seed coat can prevent the seed germination. The inhibitory substances such as the phenolic acids, coumarin and short chain fatty acids are seen in the embryo, endosperm or seed coat.
  5. The most common inhibitor of seed germination is the phytohormone abscisic acid (ABA).
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