THE FOLIC ACID COMPLEX 



16. FOLIC ACID IN fflGHER PLANTS 



Nothing appears to be known concerning the importance of folic 

 acid for higher plants. It is known to be present in some green 

 leaves, spinach leaves being the source from which it was originally 

 isolated (see page 457). 



The amount of folic acid in oats, wheat, barley and maize ^ increased 

 considerably during germination of the grain. 



Reference to Section 16 

 I. P. R. Burkholder, Science, 1943, 97, 562. 



17. FOLIC ACID IN THE NUTRITION OF INSECTS 



The suggestion that folic acid is essential for the development of 

 insects was first made by Golberg et al.} who found that, although 

 larvae of the mosquito, Aedes aegypti, developed normally as far as 

 the fourth instar on a diet that included aneurine, riboflavine, nico- 

 tinic acid, pantothenic acid and biotin, the larvae then died without 

 pupating. A further factor was found necessary to bring about 

 pupation, and this was identified as folic acid which, it was suggested, 

 stimulated the formation of a pupation hormone. Neither xantho- 

 pterine nor thymine (page 513) was able to replace folic acid in pro- 

 moting pupation. Subsequently it was foimd that,^ although the 

 liver L. casei factor (pteroylglutamic acid) could replace folic acid as a 

 nutritional factor for mosquito larvae when water-extracted yeast 

 residue was present in the basal diet, it gave unsatisfactory results 

 when the yeast residue was absent. The lactone of 4-pyridoxic acid 

 and, to a lesser extent, the lactone of 5-pyridoxic acid were able to sup- 

 plement pteroylglutamic acid, although the rate of growth was lower 

 than when the yeast residue was present. This result bears a striking 

 analogy to that obtained by Scott et al. with chicks (see page 485). 



The metamorphosis of mosquito larvae has been used as a test 

 for pteroylglutamic acid in liver extracts and lurine,^ since the anti- 

 pernicious anaemia factor had no effect on pupation. 



Folic acid was also found to be essential for the growth of the 

 larvae of the beetles, Tenebrio molitor,^ Tribolium confusum,'^' ^ Ptinus 

 tectus,^ Sitodrepa panicea,^ Lasioderma serricorne ^ and Silvanus surin- 

 amensis ^ and of the moth, Ephestia kuehniella.^ With Tribolium and 

 Ephestia, the absence of folic acid resulted in very slow growth, whilst 

 with Tenebrio, growth ceased entirely. The mortality was very high 

 with Ephestia and Tenebrio. Crystalline vitamin Be was as effective 

 as synthetic folic acid in stimulating the growth of Ephestia larvae, 



512 



