S. TONZIG 

 and 



E. MARRI 



University of Milan, Italy 



Ascorbic Add As a Growth Hormone 



According to the generally accepted definition, a growth regulating 

 hormone is a substance which is produced within an organism, can 

 be translocated far from its site of synthesis, and is active, at low 

 concentration, in influencing the rate or the modalities of the process 

 of growth. There is no doubt that ascorbic acid (AA) satisfies in the 

 higher plants the two conditions of endogenous synthesis and of 

 translocation. As to the third condition, considerable evidence has 

 accumulated in recent years, showing that the concentration of AA 

 and of its derivatives is an important factor in the control of the rate 

 of growth. 



In this survey of the contributions of our laboratory in this field, 

 the following points will be considered: (1) The effects of treatment 

 with AA on the growth of whole plants and of isolated plant parts; 

 (2) the effects of treatment with AA on some physiological processes 

 different from growth; (3) some metabolic changes accompanying the 

 effects of AA on growth and related processes; and (4) the effects of 

 auxin on the AA system. 



THE EFFECTS OF TREATMENT WITH ASCORBIC ACID 



Intact Plants 



In 1950 Tonzig and Trezzi (20) showed that the growth of the 

 shoot organs of oats, peas, beans, lupine, and castor beans is markedly 

 inhibited by treatment with AA, applied either as lanolin paste to the 

 base of the shoot or added as a solution to the nutrient medium (20). 

 This effect was mainly due to the inhibition of cell elongation, al- 

 though also the rate of cell division was decreased. Determinations 

 of AA contents in the treated tissues showed that the experimentally 



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