The growth of a seed is completely arrested after it is fully developed. Such seeds will germinate if they are supplied with water and suitable temperature. In many cases the seeds do not germinate even if they are provided with all the best conditions. The completely dry ripe seed is physiologically inactive and is said to be in a resting stage. The seed is said to be dormant and the phenomenon is termed as dormancy.
i) By being impermeable to water the impermeability of seed coat to water and oxygen does not allow the seed to germinate.ii) In certain wild plants the hard seed coat acts as a physical barrier to the expansion of the embryo.