DORMANCY IN SEEDS 



99 



creases as after-ripening progresses." Fig. 34 shows the changes in catalase, 

 Upase, and peroxidase as after-ripening proceeds. Lipase has the function 

 in hydrolyzing the important storage substances, fats. Fig. 35 shows 

 change in catalase, peroxidase, and lack of change in emulsin as Sorbus 

 embryos after-ripen.^'* In this seed also there is no appreciable increase 

 in amylase with after-ripening. This is to be expected, since there is no 

 starch in the embryo until germination occurs. 



-[ — r 



# Catalase 



Peroxidase 



-<3 (SEmulsin 



control I 



J_ 



J_ 



_L 



J_ 



_1_ 



_!_ 



_L 



_L 



SEEDLINGS 

 J I L 



5 6 7 8 9 10 II 12 13 14 

 WEEKS OF STRATIFICATION 



16 



Figure 35. Changes in the catalase, peroxidase, and emulsin activities of Sorbus 

 aucuparia seeds while after-ripening at 1° C (34° F). 



In every case reported above, catalase has sho^^^l a great increase with 

 degree of after-ripening of the seed or embryo. This enzyme decomposes 

 hydrogen peroxide, and also organic peroxides; it is found in all living 

 matter, increasing in general proportion but not in strict proportion to the 

 physiological and metabolic activity. We know little about its function 

 in organisms; it may aid in protecting them against over-accumulation of 

 organic peroxides. The change in catalase content has received a great 

 deal of attention in connection with after-ripening, germination, and stor- 

 age of seeds. In connection with after-ripening. Fig. 36 is of interest. It 

 shows the modification in the catalase content of Sorbus embryos main- 



