Continuous Respiration Studies of Dormant Seeds of Xanthium

1. There is a notable increase in the respiration rate of dry seeds during the first day of subjection to favorable germinative conditions in the respirometer. 2. After this initial increases, the respiration rate falls rapidly, with some slight fluctuations during the second and third days, to a low level, after which there is a very slow decrease in rate as long as the experiment is continued. 3. If the seeds are soaked in cold water previous to placing them in the germinator, the respiration rate reaches its maximum earlier than unsoaked seeds; otherwise the curve of respiratory activity is the same as in unsoaked seeds. 4. If the seeds are taken from the respirometer and dried, and again placed in the respirometer, they always show the increased respiration immediately after being placed in germinative conditions. 5. The weight changes occurring in seeds during long periods of dormant respiration have also been noted and compared with the respiration data. The experiments did not run long enough to give the natural rate of carbon loss from respiration in nature. 6. Respiratory activity and catalase activity in these seeds run parellel throughout the period of dormancy.