CHAPTER V 



THE EFFECT OF CHEMICAL AGENTS ON GROWTH 



The record of the effect of chemical agents on growth 

 may be taken on either a stationary or a moving plate. 

 The method of application is as follows : for the study of 

 the action of gases and vapours, the plant is enclosed in a 

 cylindrical chamber constructed of a sheet of mica provided 

 with inlet and outlet pipes for circulation of different gases 

 and vapours, the chamber being maintained in a humid 

 condition by pieces of sponge soaked in water. In the case 

 of liquid chemical agents, the specimen is suitably mounted 

 in a glass cylinder filled with water, and the normal rate of 

 growth recorded. This remains constant for about an hour, 

 in the course of which the experiment should be concluded, 

 as prolonged deprivation of oxygen affects the growth of 

 the plant. After taking the normal record, the chemicals 

 are added to the water, and the strength of solution gradually 

 increased. The chemical agents may be broadly divided 

 into three classes : (i) stimulants ; (2) anaesthetics ; and 

 (3) poisons. 



Effect of Stimulants 



Experiment 14. Hydrogen Peroxide. — A i per cent, 

 solution of this agent was often foimd to enhance the 

 rate of growth ; in some cases the enhancement was as 

 much as two and a half times the normal rate. 



Effect of Anaesthetics 



The results given below indicate that Carbonic Acid Gas, 

 Ether, and Chloroform act as mild or strong anaesthetics 

 in the above order. 



