Write a short note on seed dormancy.

Explanation

The inability of seed to germinate or grow is called seed dormancy . It may be due to either external or internal factors .
Internal factors :
A. Immature embryo : The embryo has not reached morphological maturity ,capable of germination . E.g : Ranunclus .
B . Hard seed coat : In fabacease members , seeds have hard seed coats which prevent uptakee of oxygen or water . it can be broken by scarification .
C. Chemical : Seeds of some plants contain chemicals which inhibit germination . E.g : Tomato .
External factors : Low temperature treatment : Many seeds will not germinate until they have been exposed to low temperature .The practice of layering seeds in sand and peat is called stratification . E.g : Polygonum .