RESPIRATION OF SEEDS. 75 



In 1832, Aug. Pyr. De Candolle wrote in the second volume of his 

 Physiologic Vegetale that the vitality of seeds would be prolonged if 

 they were buried sufficiently deep in the soil to protect them from 

 oxygen (or air) and moisture. Unfortunately, De Candolle did not 

 discover the true cause of this prolonged life, for nowhere did he 

 make any reference to respiration. Nevertheless his general conclu- 

 sions were properly drawn. De Candolle also stated that light acceler- 

 ates evaporation in seeds and thus causes a premature death. Here, 

 however, his results were wrongfully interpreted. These conclusions 

 are applicable only in case of seeds that die if allowed to become dry. 

 The real effect of light is to cause a slightly accelerated respiration 

 and consequently a greater deterioration in vitality. Jodin a states 

 that light accelerates respiration to a marked degree. His experi- 

 ments were with peas which contained 10 to 12 per cent of moisture. 

 Two samples of peas were placed, each under a bell jar, over mer- 

 cury. One sample was kept in the light and the other in the dark. 

 At the end of 4 years 6 months and 14 da}^s an analysis of the con- 

 fined air from the sample kept in the light gave the following results: 



Peas, 3.452 grams, in air, in light: Percent. 



Oxygen 19. 1 



Nitrogen 78. 6 



Carbon dioxid 1.2 



At the end of 4 years 7 months and 14 days an analysis of a .sam- 

 ple of air taken from the other chamber was as follows: 



IVas, 3.580 grams, in air, in dark: Percent. 



Oxygen 20. 8 



Nitrogen 79. 1 



Carbon dioxid _ .1 



The 3.452 grams of peas that were subjected to the influence of the 

 action of light had absorbed, in the given time, 2.4 cc. of oxygen and 

 produced 1.8 cc. of carbon dioxid. The seed kept in the dark showed 

 but little signs of respiratory activity. Germination tests of the 

 former showed the peas to be dead, while five peas from the sample 

 kept in the dark germinated perfectly. 



While there is no question that light exerts some influence on respi- 

 ration, still the above results do not furnish sufficient data to establish 

 the fact that respiration practically ceases in the absence of light. In 

 fact, experiments have shown that respiration is also quite marked in 

 case of seeds stored in the dark, and the difference is very slight if the 

 same temperature be maintained. 



Van Tieghem and Bonnier, in their "Recherches sur la vie latente 

 des graines," 6 demonstrated that 7.976 grams of peas, sealed, in air, 



Ann. Agron., 23: 433-471, 1897. 

 &Bul. Soc. bot. France, 29: 25-29, 1882. 



