CONTROL OF STEM GROWTH 221 



Application of gibbereliic acid reverses the light inhibition of stem 

 elongation in several species of higher plants. One species has been 

 found that shows no response to applied gibbereliic acid. It appears 

 that the light inhibition of stem growth in many plants involves a 

 mechanism by which the synthesis of the endogenous gibberellin is 

 temporarily blocked, or diverted to a side product which accumulates. 

 When plants are returned to darkness, this product appears to be con- 

 verted to active gibberellin. Promotion of stem growth by the red light 

 reaction has been found in Phaseolus vulgaris. 



REFERENCES 



Lockhart, J. A. 1956. Reversal of the light inhibition of pea stem growth by 



the gibberellins. Proc. Natl. Acad. Sci. U. S., 42, 841-48. 

 Lona, F., and A. Bocchi. 1956. Interferenza deH'acido gibberellico nell'effecto 



della luce rossa e rosso-estrema suirallungamento del fusto di Perilla 



ocymoides L. Ateneo parmense, 27, 645—49. 

 Mohr, H. 1957. Der Einfluss monochromatischer Strahlung auf das Langen- 



wachstum des Hypocotyls und auf die Anthocyanbildung bei Keimlingen 



von Sinapis alba L. (= Brassica alba Boiss.). Planta, 49, 389-405. 

 Phinney, B. O., C. A. West, M. Ritzel, and P. M. Neeley. 1957. Evidence for 



"gibberellin-like" substances from flowering plants. Proc. Natl. Acad. Sci. 



U. S., 43, 398-404. 

 Vlitos, A. J., and W. Mendt. 1957. Interactions between gibbereliic acid and 



the shoot apex of Alaska pea seedHngs. Plant Physiol. (Suppl.), 32, xlvii. 

 Went, F. W. 1941. Eflfects of liqht on stem and leaf growth. Am. J. Botany, 



28, 83-95. 



