426 



B. B. Stowe 



X 



in 



>- 

 en 



Q 



o 



^ 



u 



Q. 



O 



12 

 9 

 6 

 3 







Increase 



lAA + GA^ + 

 VITAMIN E 



IAA + GA,o' 



ASAL „/ 



B 



MEDIUM' 



basal/ 



MEDIUM 

 J_J \ I I Ly|^_l \ \ L 



I I I 



3 4 5 "^ 4 5 6 



TIME IN HOURS AFTER CUTTING 



Fig. 2. Oxygen uptake of 10 mm. 'Laxton's Progress' pea epicotyl sections during 

 log phase of growth in the presence of lAA 1.8 ^f plus GA3 0.3 fiM and methyl 

 myristate 40 f^AI plus vitamin E 10 fiAI. Basal medium 1.5 per cent sucrose -\- 

 50 nM CoClo + 5 mAf KH.PO, (pH 5.5) + 0.002 per cent Pluronic F-68. Q, 

 = fi\. Oj/mg dry wt/hr estimated from slope of best straight line through points. 

 Compare Figure 1 in Christiansen and Thimann (3). 



cytoplasmic particles (12), and in Avena coleoptiles it decreases respir- 

 ation (2). Can it be then, that in peas cobalt suppresses an alternative 

 pathway of respiration, channeling more of the energy derived from 

 sucrose towards growth? As cytochrome-c is known to be the terminus 

 of several respiratory pathways, this suggestion is particularly attrac- 

 tive in the light of the experimental results reported above. 



Assessment of the merit of these speculations will have to await 

 further experimentation. What has been firmly established is that 

 trace quantities of lipide substances can play an important role in 

 auxin action. But these lipides may not be limiting in all plant tis- 

 sues, since in Avcna coleoptiles they have not as yet been observed 

 to enhance cell elongation (16). 



This linkage of lipides to hormone action is, of course, not a new 

 suggestion. Crosby and Vlitos (6) have presented evidence that a 

 long-chain alcohol isolated from tobacco can be active in the Avena 

 first internode bioassay. Struckmeyer and Roberts (21) have for some 

 years also been working with a higher alcohol obtained from plant 



