136 



The Controlling Influence of Carbon Dioxide. Part III. — The 

 Retarding Effect of Carbon Dioxide on Respiration. 



By;FKANKLiN Kidd, B.A., Fellow of St. John's College, Cambridge ; Cambridge 

 University Frank Smart Student. 



(Communicated by Dr. F. F. Blackmail, F.R.S. Received August 26, 1915.) 



PAGE 



Introduction 136 



Section I. — The Complexity of the Respiratory Processes in Plants 137 



„ II. — Methods of Experiment 138 



„ III. — The Influence of Carbon Dioxide upon Anaerobic Respiration in 



Seeds 140 



,, IV. — The Influence of Carbon Dioxide upon Normal Respiration in 



the Presence of Oxygen in Seeds 147 



,, V. — The Influence of Carbon Dioxide upon Respiration (Aerobic 

 and Anaerobic) in Leaves. Floating and Starvation Respira- 

 tion 149 



„ VI. — Further Light upon the Chemical Mechanism of Respiration in 



Plants 152 



,, VII. — Carbon Dioxide Narcosis 154 



„ VIII. — Conclusions 155 



Introduction. 



In Parts I and II of these researches* we have been led to the conclusion 

 that the resting condition of the moist seed, so often occurring in nature, is 

 primarily a phase of autonarcosis under the action of the carbon dioxide 

 produced by the seed itself. It has been shown that retardation and 

 suspension of normal activity in plant protoplasm is produced by carbon 

 dioxide in conditions otherwise entirely favourable to growth and during a 

 stage normally characterised by vigorous growth. Attention has already 

 been called to the striking analogy existing between the dormancy of the 

 non-growing moist seed under the influence of carbon dioxide, whether 

 maturing on the parent plant or showing delayed germination in the soil, 

 and the dormancy of the unfertilised ovum. In both cases apparently 

 simple causes are found sufficient to produce a change in the cell conditions 

 owing to which the cell or tissue passes from dormancy into active growth 

 by cell, division. In neither case are the factors conditioning dormancy on 

 the one hand and growth by cell division on the other as yet clearly 

 established. A knowledge of these factors, however, must be of great 



* " The Controlling Influence of Carbon Dioxide in the Maturation, Dormancy and 

 Germination of Seeds.— Parts I and II," ' Roy. Soc. Proc.,' B, vol. 87, pp. 408 and 609. 



