ANEURINE (thiamine) 



treated with anenrine has any convincing evidence of growth-stimula- 

 tion been obtained. The addition of aneurine (o-oi mg. per litre) to 

 the nutrient solution failed to affect the fresh or dry weights of plants 

 or their times of flowering, or the size, number and colour of their 

 flowers.^ Aneurine had no effect on the growth of Agrostis tenuis or 

 Brassica alba,^ of rice,^ or of radish or cauliflower.^ It did not affect 

 pollen germination or pollen tube elongation,^ and did not promote 

 growth in, or alter the yield of, sunflowers, maize, flax, wheat or 

 beans. ^ 



Three reports have been published, however, claiming that 

 aneurine had a positive growth effect on certain plants. The first is 

 a statement ^ that the growth of aster seedlings was increased by 

 aneurine, although it had no effect on the growth of the roots ; the 

 authors suggested that aneurine might be an activator of indolyl 

 butyric acid. 



The second report claimed ^ that aneurine stimulated the growth 

 of cosmos seedlings at 20° C. but not at 26-6° C. A temperature 

 favouring luxuriant growth did not favour stimulation by aneurine. 

 The third records ® that aneurine could not replace indolylacetic acid 

 for promoting the growth of carrot tissue, though root cultures could 

 be maintained in presence of aneurine. 



A little work has been carried out on the changes that take place 

 in the distribution of aneurine as plants develop. In cereals, beans 

 and peas, no increase in the aneurine content took place diuring ger- 

 mination or, in oat seedlings, during the first five days after germina- 

 tion, although the riboflavin e, nicotinic acid and pyridoxine contents 

 increased.^** Half the aneurine present was found in the embryo, 

 although this represented only 6-5 % of the dry weight of the seed. 

 No increase occurred in the amoimt of aneurine in the coleoptile, 

 although the riboflavine and nicotinic acid contents increased. All 

 three substances appeared to be synthesised in the leaves. In tomato 

 leaves, the maximum concentration was found in newly developed 

 leaves, the concentration decreasing progressively towards the roots. ^^ 

 It would seem that aneurine is synthesised in the mature leaves 

 and translocated to the actively growing tissues, in which it accum- 

 ulates. 



The aneurine content of forty-one genera of herbs and medicinal 

 plants was 1-25 to 28-8 /xg. per g. of dry weight. 12' The amounts 

 of aneurine in a variety of foodstuffs have been listed on pages 



43 to 45. 



Although aneurine does not appear to be a growth hormone, it is 

 present in soil and natural manures, ^^ from which it is presumably 

 taken up by plants, since its concentration in pasture was increased 

 by manuring with farmyard manure. 



114 



