702 



LIGHT AND LIFE 



light are substantially reversed by the inclusion in the medium of an 

 appropriate level of sucrose, generally 1 per cent. 



By contrast, the growth of etiolated sections in the dark is markedly 

 enhanced by CMU (Fig. 14). The additional growth produced by 

 CMU is essentially completely inhibited by weak red morphogeneti- 

 cally active light. The CMU-induced growth increase, like that of 

 cobalt, is dependent on the presence of sucrose (Fig. 15) and is 

 greatest when both sucrose and lAA are supplied. CMU does not 

 alter the lAA optimum for growth (Fig. 16). 



.+SUCROSE + CMU 



SUCROSE + CMU 



/ \ +SUCROSE-CMU 



V 



rSucROSE-CMU 



-log M lAA 

 Fig. IG. Effect of p-chlorophenyl dimethyl urea (CMU) and sucrose on the 

 indole acetic acid (lAA) optimum of etiolated pea stem sections. 



TABLE 8 



Interaction of Fenuron, Sucrose, and Indole Acetic Acid (IAA) on the 



Growth of Etiolated Pea Stem Sections 



