56 THE PLANT CELL WALL 



Antioxidants which 

 promote growth and 

 inhibit lignin synthesis 



Oxidants which 

 inhibit growth and 

 enhance lignin synthesis 



In addition to the foregoing substances, the more familiar 

 biological reductants such as ascorbic acid and glutathione and 

 dehydrogenases have been proposed as inhibitors of lignin synthesis. 

 Metabolites which affect cellular reducing power including glucose- 

 1 -phosphate, glycerol, Krebs cycle acids and adenylic acid also 

 inhibit the experimental formation of lignin. Finally, more general- 

 ized inhibitions have been attributed to aspartic acid, arginine, 

 lysine, glycine, Ca (II) and Mg (II). In general then, those substances 

 characteristic of the young growing cell with high levels of hydrogen 

 transport activity suppress lignification. 



Incomplete as our present knowledge of cell wall regulation 

 may be, there are nevertheless the outlines of a highly functional 

 process relating growth, differentiation, hormones and metabolism. 



II. The Lysis of Cell Walls 



Although they are somewhat removed from the intensive activi- 

 ties of the protoplast, cell walls are nonetheless dynamic cellular 

 constituents, subject to the action of various hydrolytic enzymes. 

 Enzymic attack upon cell wall substance may originate within 

 protoplast itself, or may result from the action of enzymes released 

 by other cells or organisms. 



Functionally, cell wall lysis may be associated with several 

 kinds of biological behavior or interactions among organisms: 



(a) Resorption of formed wall structures occurs during growth 

 and development. In insects, the production of new cuticle under 



