35. What is seed dormancy ? How can it be broken artificially ? 

Dormancy is a mechanism to prevent germination during unsuitable ecological conditions, when the probability of seedling survival is low. One important function of most seeds is delayed germination, which allows time for dispersal and prevents germination of all the seeds at the same time.


Breaking of Dormancy in Seeds : In some plants light plays an important role in germination. Certain varieties of cabbage and lettuce fail to germinate in darkness. But when exposed to light, even briefly, they germinate quickly. In such seeds the red region of visible spectrum has been found to be the most effective for germination.