BIOCHEMICAL CHANGES IN BREAKING AND 

 INDUCING DORMANCY IN SEEDS 



A. M. MAYER 



Department of Botany, Hebrew University, 

 Jerusalem (Israel) 



The term dormancy is one which is used in various senses by 

 various authors and this is particularly the case as regards the 

 dormancy of seeds. In this paper, it is intended to use the term 

 as referring to a population of seeds, specifically here lettuce 

 seeds. If such seeds are placed under specified conditions of 

 temperature and moisture, usually 26° in the dark, on moist 

 filter paper, a certain number of them will germinate. The 

 percentage of seeds which germinate under these conditions 

 gives a measure of the dormancy of this seed population. This 

 percentage can be altered in various ways, e.g., it can be in- 

 creased or decreased by a number of physical and chemical 

 agencies. Those which increase the percentage of germination 

 may be considered as dormancy-breaking, while those which 

 cause a decrease without, however, affecting irreversibly the 

 eventual ability of the seeds to germinate when some other 

 treatment is given, will be considered as inducing dormancy. 

 From this it is immediately clear that, in referring to biochemical 

 changes occurring during induction and breaking of dormancy, 

 what is in fact being considered is the overall biochemical 

 behaviour of a population of seeds under different treatments. 

 In fact, the action of a dormancy-breaking and dormancy- 

 inducing substance is always considered relative to the behavior 

 of the untreated seeds. In no case is there any certainty that a 

 specific change has occurred within any one given seed, and 

 indeed, no attempt has ever been made to try and analyse 

 individual seeds. This is for two reasons. 



First, lettuce seeds are extremely small and inconvenient to 

 handle individually. The second and more important reason is 

 that there is no way of foretelling whether any given seed will or 



References p. 198 



