TRACE ELEMENTS IN PLANTS 123 



ether and alcohol was necessary to denature the proteins before 

 these tests gave a positive result, thus indicating the degeneration 

 of the proteins of the cells with high acidity and ammonia 

 nitrogen content. The disturbance in the carbohydrate and 

 nitrogen metabolism of the boron-deficient plants may be 

 attributed to a disturbance of the normal oxidation-reduction 

 relations of the cells, and it has been pointed out by Johnston 

 and Dore (1929) and Eaton (1935) that boron has considerable 

 affinity for the hydroxy groups of polyhydric alcohols. 



Heggeness (1942) has recently suggested that boron may play 

 a considerable part in protecting flax from attack by the rust 

 Melampsora Lini. Borax was applied to the soil at the rate of 

 60 lb. per acre, 2 weeks after germination of the flax, which was 

 sown on 9 May 1941. Some 10 weeks later plants on control 

 plots which did not receive boron showed 100 per cent infection, 

 while plants on the boron-treated plots showed very little 

 infection in the field. When leaves from boron- treated plants 

 were cleared with 80 per cent alcohol many points of infection 

 could indeed be seen, but they mostly failed to develop. With a 

 sowing later in the year, made on 16 June, the boron-treated 

 plants were not so free from rust, but were yet very much freer 

 from rust than the controls. 



