S. HOUSLEY 



and 



B. J. DEVERALLi 



Unilever Ltd. 



Sharnbrook, Bedford, England 



The Influence of GibberelUc Acid on lndole-3- 

 acetlc Acid Disappearance From Solutions 

 Containing Excised Pea Stem. Tissues and 



I ndole-3 -acetic Acid Oxidase 



Since 1957 it has been widely recognized that the gibberellins can 

 markedly modify plant growth and development including, for ex- 

 ample, changing the quantity of solid matter in various tissues (2, 7, 

 23), replacing the light requirement for germination of light-sensitive 

 seeds (14), and influencing the time of flowering (17, 26). Their 

 most characteristic property, however, is the ability to promote stem 

 elongation in many plants, including tall and dwarf varieties of pea, 

 the latter showing the greater increase in growth rate (3). Using 

 seedlings of 'Alaska' pea grown in complete darkness, Lockhart (20) 

 obtained little or no response to applied gibberellins. When seedlings 

 the growth of which had been inhibited by red light were treated, 

 their growth rate was restored to that in darkness. On the other 

 hand, with the dwarf 'Progress No. 9,' growth rate in darkness was 

 increased under the influence of gibberellins, but this enhanced 

 growth was also equalled by gibberellin-treated dwarfs grown in light. 

 Rather different results have been obtained by Brian and Hem- 

 ming (4) with segments excised from stems of dwarf 'Meteor' pea. No 

 increased elongation with gibberellic acid (GA) in light was obtained 

 with sections from light-grown plants, whereas in the dark, with sec- 

 tions from dark-grown plants, Brian, Hemming, and Radley (6) ob- 



^ Subsequently: Department of Plant Pathology, University of Wisconsin, Madi- 

 son 5, Wisconsin. Botanv Department, Imperial College of Science and Technology, 

 London, S.W. 7. " 



[627] 



