NICOTINIC ACID (nIACIN) 



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16. EFFECT OF NICOTINIC ACID ON HIGHER PLANTS 



Comparatively little study has been made of the nicotinic acid 

 requirements of the higher plants. According to J. Bonner,^ nico- 

 tinic acid is indispensable for pea seedlings, whilst orchid seeds are 

 said 2 to require the presence of nicotinic acid or pyridoxine before 

 germination can take place ; with pyridoxine, however, subsequent 

 growth was poor, whereas nicotinic acid promoted normal develop- 

 ment. Nicotinic acid may be one of the substances produced by the 

 mycorrhizal fungus. 



On the other hand, both nicotinic acid and nicotinamide markedly 

 inhibited root growth in cress seedlings.^ Nicotinic acid also en- 

 hanced the inhibitory effect of indole-3-acetic acid on the growth 

 rate of asparagus stem tips in the dark, although by itself it had no 

 effect.* No such effect was observed with cress seedlings.*" 



Considerable increases in the nicotinic acid content occurred 

 during the germination of oats, wheat, barley and maize.^ The 



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