Oxidants, Antioxidants, and GroxvUi Regulation 



351 



Table 4. The effect of anaerobic pre-conditioning on growth of cucumoer hypo- 

 cotyls. 



lAA diminished (Table 4). The data show that a period of anaerobic 

 pre-conditioning can replace the external auxin requirement, and 

 even render moderately inhibitory an ordinarily optimal lAA level. 

 Anaerobic pre-conditioning may be equivalent to addition of an anti- 

 oxidant such as Co+^ which increases growth by preventing lAA 

 destruction, or may effect a more general increase in the reduction 

 potential of the cell, delaying oxidation of many labile components. 



SUMMARY 



This paper calls attention to a new interrelationship between oxi- 

 dation and growth. The antioxidant properties of known hormonal 

 entities provide the link between these two processes. Geometrically 

 varied growth promoters share in common the ability to inhibit lignin 

 synthesis and other oxidations diagnostic of unbalanced oxidation- 

 reduction states in maturing (aging) cells. The toxic effects of oxygen 

 constitute a major contribution to degenerative changes in cell senes- 

 cence. Accordingly hormonal substances with antioxidant properties 

 have been assigned a protective role by buffering the cell against cumu- 

 lative damage by oxidants. The dynamic and continuous relation be- 

 tween oxidants and antioxidants is illustrated by substances which 

 promote growth under ordinary aerobic conditions, become survival 

 factors at elevated oxidant levels, and yet lose their effectiveness, or 

 inhibit, when the oxidant level is reduced. Three general functions 

 are proposed for antioxidants as bioregulators. First, antioxidants 

 serve as protectants for specific structures or through their general 

 effects on oxidation-reduction balance. Second, antioxidants may serve 

 as metabolic regulators by selectively blocking specific pathways. 

 Finally, as mobile electronic systems, antioxidants may act as cofactors 

 in electron transport. 



