Oct. 21. 1918 Catalase and Oxidase Content of Seeds 139 



these structures leads to very prompt and practically complete germi- 

 nation in fresh seeds, after-ripened seeds, and seeds in secondary dor- 

 mancy .^ The seedlings resulting in every case are about equally vigor- 

 ous. This indicates that the embryo itself is not dormant. As yet 

 how the inclosing structures enforce dormancy is not known. It is not 

 by the complete exclusion of water, for the intact seeds absorb water 

 rather readily; nor through reduction of the oxygen supply, for these 

 seeds are indifferent to variations in oxygen pressures varying from one- 

 fifth to five-fold that of the atmosphere ; nor to narcotic action of carbon 

 dioxid held in by the coats, as Kidd {28) has assumed to be the case for 

 all dormant seeds that absorb water readily, for caibon dioxid in high 

 partial pressures is a good forcing agent for dormant seeds of Johnson 



grass. 



CATALASE IN SEEDS 



Catalase is an enzym capable of splitting hydrogen peroxid into water 

 and oxygen. It is universally present in living matter and was 

 supposed to be a property of all enzyms until Loew (jo) showed it to 

 be a distinct body. There is some question arising as to its real enzymic 

 nature (j, 2). 



Its function in the organism is not known. Loew believed that in 

 aerobes it protected the organism against the accumulation of hydrogen 

 peroxid produced in respiration. In anaerobes he assumed that it 

 loosened chemical affinities, aiding splittings, oxidations, and reduc- 

 tions. Others have assigned it protective action against excessive 

 oxidations in the organism by organic peroxids or even an essential part 

 in respiration (27, p. 138-140). Whatever its function Zieger (57) has 

 shown some correlation between catalase content and metabolism in 

 animals, and several workers (2, 12, 13, 29, 32) have shown a rather 

 close correlation between respiratory intensity and catalase activity. 



EXPERIMENTAIv METHODS 



The catalase activity was determined by an apparatus similar to that 

 used by Appleman (z). A given weight of seed material, after being 

 groimd in a mortar and worked through a piece of bolting cloth of de- 

 sirable mesh, was shaken up in the bottle of the apparatus with 5 cc. of 

 distilled water. Then 5 cc. of hydrogen peroxid, rendered neutral to 

 phenolphthalein by the addition of Njio sodium hydroxid, was placed 

 in the dropping funnel and the bottle and dropping funnel lowered into 

 a water bath at 25° C. After the apparatus with its contents had reached 

 the temperature of the water bath the hydrogen peroxid was dropped 



into the plant emulsion and the mixture continuously shaken. The 



■ * ' ■ — 



2 One of the best ways to remove these structures is to pick the caryopses out of the scales and treat them 

 in the air-dry condition for two or three minutes with concentrated sulphuric acid. This treatment is 

 followed by thorouKh washing, first with a s per cent solution of sodium hydroccn carbonate and later with 

 distilled water. In the last washing care should be taken to rub away all the carbonized material. 



