Factors Affecting Seed Dormancy – Class 11 | Chapter – 15 | Biology Short Notes Series PDF

Factors Affecting Seed Dormancy: Seed Dormancy is the state of the slow growth of seeds or other plant organs caused by internal factors. It is also known as the rest period. The plant benefits significantly from the dormancy of seed as they require a specific period of rest before they are able to germinate.


Factors Affecting Seed Dormancy

  • Water Impermeability of seed coats

At maturity, the seed coverings of several species are totally impenetrable to water. Many legume seeds (e.g, clovers, alfalfa, etc), as well as water lotus and morning glory seeds, have this characteristic. Water must enter the seed coverings for germination to take place.

  • Oxygen Impermeability of seed coats

The two seeds in a cocklebur (Xanthium) fruit are not dormant in the same way. The lower seed normally germinates in the spring following maturity in natural settings, while the top seed remains dormant until the following year. The impermeability of the seed covering to oxygen has been shown to be the cause of dormancy in these seeds.

  • Mechanically Resistant seed coats

Seed coatings are so strong in some seeds, such as mustard (Brassica), pigweed (Amaranthus), shepherd’s purse (Capsella), and others, that they do not yield to the pressure of the developing embryo. If the seed coats are removed, the embryos of these seeds have no dormancy period and will grow rapidly.

  • Dormant Embryos

Even when the embryos are fully grown when the seed is ripe, seeds of many species fail to germinate, even when the environmental conditions are ideal. The physiological state of the embryo causes dormancy in such seeds. Even if the seed coverings are removed, the embryos of such seeds will not grow when they first mature.

  • Rudimentary Embryos

When the seed is shed in plants like ginkgo (Ginkgo biloba), European ash (Fraxinus), holly (Ilex), and many orchids, the embryo is disorganised and develops fully before germinating.

  • Low Temperature

As certain plants require a low temperature for germination, their seeds remain dormant even after harvest. These seeds germinate then in spring.

  • Immaturity of the Embryo

Immaturity of the embryo occurs in the seeds of plants such as Orchids, Ginkgo, and others because the embryo fails to mature when the seeds are shed.

  • Light sensitive seeds

The light affects the germination of some seeds, the absence of light causes the seeds to go dormant. Photoblastic seeds are those that are sensitive to sunshine and germinate due to light, whereas negatively photoblastic seeds are those that have their seed germination inhibited by light.

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By Team Learning Mantras