[ 414 ] 



XXXI. 



THE HYDEOGEN lOF CONCENTEATION OF PLANT CELLS. 



By W. E. G. ATKINS, O.B.E., Sc.D., F.LG. 



[Cominunicatecl by Professor H. H. Dixon, Sc.D., F.E.S.] 



[Reafl NovEMKi'.R 22, 1921. Published Febuuary 2, 1922.] 



CONTENTS. 



PAGE 



Introduction, ..... 414 



Hydrogen ion concentrations met with 

 in plants, ..... 415 



Determinations involving small quantities 

 of liquid, 416 



Determinations of hydrogen ion con- 

 centrations in pl.nnt tissues, . .417 



Hydrogen ion concentrations of plant 

 secretions and exudations, . . .421 



Relation of the natural acidity of plant 

 tissues to the activity of their enzymes, 423 



Indicators for use with plant tissues, . 425 



Summary, . . . . , .426 



Introdiwtion. 



An exact knowledge of the reaction of living cells is a necessity for the study 

 of the chemical changes taking place in their metabolism. That this is so 

 will be appreciated by a consideration of the influence of hydrogen ion 

 concentration upon such changes as, for example, the molecular rearrange- 

 ments of the sugars as studied by Nef (1911), or the rates of oxidation of 

 sugars and of cystein (Mathews, 1909). In enzyme chemistry the con- 

 trolling influence of the hydrogen ion concentration has been strikingly 

 demonstrated by numerous researches, such as those of Sorensen (1909) upon 

 invertase, catalase, and pepsin; of Michaelis (1909, 1914) upon invertase 

 and malt diastase ; of Bunzel (1916) and of Eeed (1916) on oxidases ; 

 of Okada (1916) on the proteoclastic action of taka-diastase ; of Frankel 

 (1917) on papain; of Sherman, Thomas, and Baldwin (1919) upon three 

 typical amylases ; of Harvey (1920) on catalase in diseased leaves. 

 Furthermore, the hydrogen ion concentration has been found to regulate the 

 physical condition of proteins and similar substances ; axcounts of work in 

 this line are given by Loeb (1918), Eobertson (1920), MacDougal (1920), 

 Cohn, Gross, and Johnson (1920), and ZoUer (1921). For a full biblio- 

 graphy, that given by Clark (1920) may be consulted. It contains over 

 eleven hundred references ; and the list given by Schmidt and Hoagland 

 (1919) has over foitr hundred and fifty. 



