Dormancy vs. Chill Hours

David C. Logan david.logan at
Mon Apr 21 03:58:06 EST 1997

faganjohns wrote:

>All plants are dormant until they germinate.  That is, things like 
>temperature, cold-wet conditions (stratification), and light 
>are all just mechanisms that aid in breaking dormancy.  Most seeds of 
>species, except many wetland species, have multiple dormancy 
>This allows the plants to germinate at the optimum time.  If all of a
>seeds dormancy mechanisms are not triggered the appropriate amount 
>can overshadow others of course), the seed will not germinate.

The first part of this answer is not striclty true since many seeds show 
no dormancy and will germinate as soon as suitable envirmonmental 
conditions prevail - the lack of germination while one of these 
conditions is not met is not dormancy but quiescence. If a seed is 
dormant then it will not germinate even if all the required 
envirmonmental conditions prevail but will do so after the dormancy is 
broken by (depending on species) increased time after seed shed 
(afterripening), exposure to high or low temperature, passage through an 
animal etc etc.

david.logan at

David C. Logan
Department of Plant Science
University of Oxford
South Parks Road

Tel: (01865) 275024 (direct)
FAX: (01865) 275074

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