Oct. 21, I918 



Catalase and Oxidase Content of Seeas 



169 



oxidase activity of 250-mgni. samples of fresh seed of Tunis grass- 

 sorghuni hybrid and of Johnson grass seed in secondary dormancy with 

 Ml 2,000 mercuric chlorid replacing distilled water in the oxidase baskets. 

 The results with distilled water are also given. 



The mercuric-chlorid solution had only a slight depressing effect upon 

 oxidase activity. Either this oxidase is very much more resistant to 

 mercury poisoning than some other enzyms or else the concentration of 

 the solution was very greatly reduced by adsorption to the large amount 

 of powder used, McGuigan (jz) found the activity of diastase com- 

 pletely inhibited by M 1 30,000 mercuric chlorid. Caldwell {14) showed 

 that the activity of bromelin was completely inhibited by M/4^,000 to 

 Ml 75, 000 mercurous nitrate (HgNOg) and mercuric nitrate Hg(N03)2. 



Table XXXII. — Effect of MjSyOoo mercuric chlorid upon oxidase activity 



Material. 



Reagent. 



Reduction of pressure. 



Tunis grass-sorghum hybrid 

 (collected on Sept. 14, 

 1917.) 

 Do 



Johnson grass 8599 (col- 

 lected on Sept. 23, 1916), 

 incubated at 20° C. 



Do 



Pyrogallol + MJ2,ooo mer- 

 curic chlorid. 



Pyrogallol in distilled 



water. 

 Pyrogallol -1- Ml2,ooo mer- 



ciuric chlorid. 



Pyrogallol in distilled 

 water. 



16 mm. in 6 hours. 



20 mm. in 6 hours. 

 12.5 ram. in 6hotirs. 



14 mm. in 6 hovu-s. 



SUMMARY 



(i) Measurement of the oxygen liberated from hydrogen peroxid by 

 the addition of an excess of powdered seeds (plant catalase) provides a 

 convenient method of determining the concentration of the hydrogen 

 peroxid used. 



(2) In the determination of the catalase of seeds it is necessary to 

 neutralize the hydrogen peroxids used, for the acidity in all commercial 

 hydrogen peroxids tried was sufficient to reduce greatly the catalase 

 activity. The seeds studied bear no inhibiting acids, but show buffer 

 action against the acids of the hydrogen peroxids. 



(3) Excessive pulverization of seeds reduces their catalase activity. 

 Powder of Johnson grass gave maximum activity when passed through a 

 7o-to-8o-mesh bolting cloth, and crimson clover when passed through a 

 1 00- mesh. 



(4) In powdered seed material (Johnson grass) stored in a desiccator 

 at room temperature the catalase degenerates rather rapidly, losing 

 70 per cent of its activity in 54 days. Morphological integrity insures 

 much slower degeneration. 



(5) In the embryo of wheat the catalase activity is 28 to 29 times that 

 of the endosperm. Burlakow (4) found the respiratory activity of the 



