Positively photoblastic seeds germinate only in the presence of

Give scientific reasons: Dry seeds do not germinate.

In some plants,seed germination can be induced by mechanically breaking the hard seed coat. This phenomenon is known as:

Which of the following is not a man-made method to overcome seed dormancy?
$(I)$ Seed coat broken by using knives,sandpapers,etc.
$(II)$ Passage of seed through the digestive tract of animals.
$(III)$ Effect of inhibitory substances can be removed by subjecting the seeds to chilling conditions.
$(IV)$ By application of certain chemicals like gibberellic acid and nitrates.

To remove seed dormancy, we can treat seed by using this chemical.

Seed dormancy is due to the