688 Journal of Agricultural Research voi. xu.no. n 



tubers. If catalase activity parallels respiratory activity, it may be 

 reasoned by analogy that those structures of the wheat kernel which 

 exhibit the greatest catalase activity are the seat of the larger part of 

 respiration. 



Barnes and Grove {1916) lend further support to the hypothesis that 

 the seat of oxidation activity is in the embryo by their obsenl^ation that 

 in air-dry wheat the embryo becomes shrunken after a time, while the 

 food materials of the endosperm are unimpaired. This is interpreted 

 by them to indicate a destruction of the material of the embryo itself 

 as the result of respiration when the dryness of the kernel suppresses 

 diffusion. Were respiration equally pronounced in the endosperm it 

 too should exhibit a similar loss of material. 



Osterhout's (1917) observation that oxidation is more rapid in the 

 nucleus than in the cytoplasm might lead to the deduction that, since 

 the embryo cells of the wheat caryopsis have a much larger proportion 

 of nuclei than the endosperm cells, oxidation should proceed more rapidly 

 in the embryo tissues. 



All of the above facts are in harmony with what might logically be 

 expected. The principal release of energy as the result of biological 

 combustion should occur in the structure where such energy is required 

 for the synthesis of new organic compounds. Since the embryo is 

 endowed particularly with that function, respiration must of necessity 

 be most pronounced in it, if not confined to it. 



MEASUREMENT OF THE RATE OF RESPIRATION 



There are two general methods which may be used in the quantita- 

 tive estimation of the rate of respiration of vegetable material. One 

 that is employed where faciHties are available is to measure in terms 

 of Calories the heat energy released per unit of time and material. The 

 elaborate device for this purpose is known as the respiration calorimeter. 

 The second general method includes the determination of one of the end 

 products of the reaction, carbon dioxid. This method may easily be 

 made decidedly accurate without entailing the assembling of a calori- 

 meter. In using the calorimeter both carbon dioxid respired and heat 

 evolved may, if desired, be determined simultaneously. 



Inasmuch as the writers were not provided with a respiration calori- 

 meter suited to this purpose, the carbon dioxid evolved b}^ stored wheat 

 was measured, and from this data the rate of respiration was calculated. 

 Truog's {1915) method and absorption tower was used for this purpose, 

 the tower being slightly modified, or rather, added to, in order to adapt 

 it to the present work. The procedure followed and a description of 

 the apparatus has been published by the junior author (Gurjar, 19 17). 

 To compute the Calories of heat evolved, the factor found by Langworthy 

 and Milner may be employed; i gm. of respired carbon dioxid equals 

 2.6 Calories of heat. 



