100 BOTANY. 



Demonstration 28. 



17SL Respiration in a leafy plant. — We may take a potted plant which 



has a well-developed leaf surface and place it under a tightly fitting bell jar. 



Under the bell jar there also should be placed a 



small vessel containing baryta water. A similar 



apparatus should be set up, but with no plant, to 



serve as a check. The experiment must be set up 



in a room which is not frequented by persons, or 



the carbon dioxide in the room from respiration will 



vitiate the experiment. The bell jar containing the 



plant should be covered with a black cloth to prevent 



starch formation. In the course of ten or twelve 



Test for' g 'lib°ration of hours . if everything has worked properly, the baryta 



carbon dioxide from leafy wa t e r under the jar with the plant will shew the film 



giant during respiration. ■* * .,, , 



aryta water in smaller of barium carbonate, while the other one will show 

 vessel. (Sachs.) none Respiration, therefore, takes place in a leafy 



plant as well as in germinating seeds. 



Synopsis. — Respiration (taking in oxygen and giving off carbon dioxide) 

 occurs in all plants during growth. 



Respiration takes place actively in germinating seeds and opening buds 

 and flowers. 



Respiration without access of oxygen (intramolecular respiration) takes 

 place, in germinating seeds for example, in addition to normal respiration. 



Respiration in plants is the same process as in animals. 



The carbon dioxide from respiration may be detected by testing the air in 

 the vessel where the plant is growing with a lighted taper (the taper is ex- 

 tinguished), or by baryta water (the baryta water absorbs carbon dioxide, 

 forming the insoluble barium carbonate), or by lime water (the lime water 

 absorbs carbon dioxide, forming the insoluble calcium carbonate = chalk). 



Access of oxygen is necessary for the growth of most plants. (Some bac- 

 teria will only grow in the absence of oxygen. ) 



Respiration is a breaking-down process. (Changes take place in the pro- 

 toplasm, the entering oxygen uniting with some of the carbon and oxygen of 

 the protoplasm and forming CO a .) Compare this with the burning of plant 

 substance. 



Respiration transforms energy in the plant, which is manifested by an 

 elevation of the temperature of the plant substance, so that the plant gains 

 some heat ; it is also manifested by growth. 



