SIGNIFICANCE OF WATER 89 



the involved problems, and necessitates a much greater 

 up- take of oxygen in those instances where fats are the pre- 

 dominating respirable material as compared with those in 

 which carbohydrate is the prime respirable substance, that is, 

 the respiratory quotient of a fat-containing seed is of a com- 

 paratively low value. To what extent the products of the 

 hydrolysis of fats are immediately respirable, is another aspect 

 of the subject awaiting investigation. 



WATER. Since an ordinary living plant is mostly water, 

 it is obvious that any circumstance which leads to a marked 

 increase or decrease of water may alter profoundly the ex- 

 pressions of life ; thus if water be removed from a plant to an 

 extent sufficient to make the cells flaccid, growth will come 

 to an end and therefore the respiratory activity will be 

 ultimately considerably lessened. This statement is intention- 

 ally qualified, for an increase and also a decrease in the water 

 supply may lead to an immediate amplification in the intensity 

 of respiration. Maige and Nicolas * found in several instances 

 that a rise in turgescence is followed by an increase in 

 respiratory activity and a similar result obtains, although to 

 a lesser degree, when a decrease in turgescence is brought about 

 in similar material either by natural evaporation or by the 

 action of a mildly plasmolyzing sugar solution. If a further 

 removal of water be effected by the use of a 10 to 20 per cent 

 solution of glucose, a decrease in respiration, as indicated by 

 a smaller intake of oxygen and output of carbon dioxide, 

 results. Smith f similarly observed that vegetative organs of 

 the snowdrop, the bean, and Tropceolum, after drying in a 

 desiccator until a third to a half of the water had been 

 removed, showed a greater respiration as compared with 

 normal members of the plants mentioned. Up to a loss of 

 30 per cent of water the respiratory activity increased in pro- 

 portion to the amount of water lost ; from 30 to 60 per cent 

 loss of water the respiration was uniform at the increased rate 

 attained with the 30 per cent loss ; finally, with a loss of from 

 60 to 100 per cent of water the respiration decreased propor- 

 tionately to the amount of water removed. All plants do not 



* Maige and Nicolas : " Rev. ge"n. Bot.," 1910, 22, 409, 

 f Smith: ''British Ass. Rep.," 1916, 8$, 725. 



