Characteristics of an Itihibitor From Woody Shoots 139 



SUMMARY 



Shoots of the plum rootstock 'Myrobalan B' extracted with ether 

 yielded material which, when separated on paper chroma tograms, 

 was inhibitory to coleoptile extension. This material was tested in 

 various ways, with the following results. 



Inhibition: coleoptile section extension with or without added 

 promoter (sodium salt of indole-3-acetic acid = NalAA) and when 

 supplied to either end of the section; coleoptile curvature due to 

 unilaterally applied auxin (but less sensitive than section growth); 

 wheat leaf-base extension in the presence or absence of NalAA or GA 

 (gibberellic acid); pea stem section extension; apple pollen tube exten- 

 sion; cress root extension. 



Augmentation of auxin effect: slit pea stem inward curvature due 

 to auxin was increased by inhibitor. 



No effect: abscission of Coleus and Phaseolus explants; respiration 

 of coleoptile sections; water loss during plasmolysis of potato discs 

 or water uptake after plasmolysis; transport of NalAA basipetally 

 through coleoptile sections was not hindered by inhibitor. 



Recovery of coleoptile sections is considerable, and depends on 

 the severity of the inhibitor treatment before releasing the inhibi- 

 tion by washing in water. 



Our lack of knowledge on the nature, mode of action, and func- 

 tion in the plant of such inhibitors is stressed, and study of these sub- 

 stances by chemists and biochemists called for. 



LITERATURE CITED 



1. Barlo\v, H. W. B., and Hancock, C. R. Studies on extension growth in cole- 

 optile sections. III. The interaction of temperature and /3-indolylacetic acid on 

 section growth. Jour. Exper. Bot. 10: 157-168. 1959. 



2. , Hancock, C. R., and Lacey, H. J. Some observations on growth in- 

 hibitors extracted from woody shoots. Rep. E. Mailing Res. Sta. 1954: 115-121. 

 1955. 



Hancock, C. R., and Lacey, H. J. Studies on extension growth in 



coleoptile sections. I. The influence of age of coleoptile upon the response of 

 sections to lAA. Ann. Bot. II. 21: 257-271. 1957. 



4. Burton, W. G. Some observations on the growth substances in ether extracts 



of the potato tuber. Physiol. Plant. 9: 567-587. 1956. 



5. Choudhuri, S. H. Auxin synthesis in embryos. (Auxin production by rye 

 embrvos, and the effect of external auxin supply on excised rye coleoptiles.) 

 Ph.D. Thesis, London University. 1957. 



6. Hancock, C. R. Studies on extension growth in coleoptile sections. II. The 

 effects of high concentrations of /3-indolylacetic acid on section growth. Ann. 

 Bot. II. 23: 107-119. 1959. 



7. Housley, S., Bentley, J. A., and Bickle, A. S. Studies on plant growth hor- 

 mones. III. Application of enzyme reaction kinetics to cell elongation in the 

 Avena coleoptile. Jour. Exper. Bot. 5: 373-388. 1954. 



8. , and Taylor, W. C. Studies on plant-growth hormones. VI. The na- 

 ture of inhibitor-^ in potato. Jour. Exper. Bot. 9: 458-471. 1958. 



