Changes in Buds and Seeds in Response to Chilling 



99 



ing about a reduction in the level of inhibitor? If the inability of 

 dormant embryos to grow is due to the presence of the inhibitor, then 

 it ought to be possible to show that removal of the inhibitor permits 

 growth. Conversely, it ought to be possible to show that application 

 of inhibitor to nondormant embryos prevents their growth. 



An experiment was carried out to determine whether leaching of 

 the dormant embryos would enable them to germinate. The embryos 

 were dissected out from the seeds which had been imbibed at labor- 

 atory temperatures for some time. These embryos and an equal 

 number of intact seeds from the same sample were then soaked in 

 water for 48 hrs. The embryos were then dissected out from the 

 washed seeds, both series of embryos were then placed directly on the 

 glass of a petri dish, and wet filter paper was placed inside the lid of 

 the upper dish. In this way any further leaching of inhibitor during 

 the germination test was precluded. Within 3 days the embryos from 

 which the endosperm and testa had been removed before soaking had 

 germinated, whereas the embryos which had been removed from the 

 seeds after the period of soaking remained dormant (Figure 4) . It 

 was found that chilled embryos were capable of germinating under 

 the same conditions even without leaching, so that it seems unlikely 



Untreated 



Mature 



Vernalized 



A 





B 



:i\M 



iiiiiiii*'^ 



■--mmiJ^ 



Fig. 4. Effect of leaching on dormancy of embryos of F. excelsior. Embryos in row 

 A were soaked naked 48 hrs. whereas those in row B were derived from intact seeds 

 which had been soaked 48 hrs. and the embryos excised after the leaching treat- 

 ment. 



