294 PLANT PHYSIOLOGY 



Production of Water. — As seen from the respiratory equation, 

 water is one of the products formed. Since water plays such an 

 important role in the plant, is found in all parts of it in larger or 

 smaller amounts, and is used in so many different reactions within 

 the organism, it is extremely difficult to determine the exact 

 amount formed by respiration. Liaskovskii (1874) studied the 

 formation of respiratory water in germinating seeds, and Bab- 

 cock (1912) made extensive studies on germinating seeds as well 

 as on insects like the clothes moth, which lives on dry wool. This 

 insect takes in practically no water and is able to live from the 

 water produced in respiration. In a similar way, the water in 

 desert plants and animals may in part be accounted for. This 

 respiratory water is of higher importance in animals than plants, 

 since the plant is only getting back in respiration the water which 

 it previously had to take in for the manufacture of the carbohy- 

 drates. To assume that such water is really being furnished the 

 plant is arguing in a circle. 



Activity of Respiration.— The formation of heat, loss of dry 

 weight, and amount of water produced, all vary with the activity 

 of the respiration, which in turn depends upon many factors (to 

 be discussed in the following pages), but to say that respiration 

 is very active is a mild statement. It is commonly thought that 

 respiration in plants is weak compared with that of animals, but, 

 when compared weight for weight, it is found that the difference 

 is not so great as one would expect in light of the greater apparent 

 activity of animals. Thus a man at light work produces about 

 1.2% of his weight in carbon dioxide every twenty-four hours. 

 Horse-chestnut (Aesculus) buds have a carbon dioxide output 

 which equals 3% of their dry weight in the same length of time; 

 poppy seedlings 2%; and molds as much as 6%. If heat effects 

 are compared, a kilogram of germinating peas will give off about 

 25% less heat per minute than a mouse ; while if the consumption 

 of oxygen is compared, young wheat leaves are found to use 

 about the same amount of oxygen per hundred grams of weight 

 as a man, unfolding flower buds four times as much, and some 

 bacteria two hundred times as much! All this indicates that 

 respiration is not as slight in plants as is often thought. 



The question arises whether respiration from plants in sleeping 

 rooms is sufficient to be dangerous to the occupants of the room. 

 While the amount of respiration is relatively high in proportion 



