96 TRACE ELEMENT DEFICIENCY 



copper per litre grew normally for 19 weeks before the symptoms 

 of copper deficiency were evident. Flowering took place but 

 grain was not formed. When the concentration of copper in the 

 culture solution was 20 fig. per litre some grain was produced but 

 a proportion of the spikelets were sterile. In cultures grown in 

 solutions containing from 50 to 500/xg. of copper per litre growth 

 was normal. If the concentration of copper was higher than this, 

 a toxic effect was observed, growth and tillering being depressed 

 while the leaves became stiff and erect. Although the leaves 

 were first of a particularly deep green colour the younger leaves 

 developed a strong chlorosis, which was more marked the higher 

 the copper concentration of the culture solution. 



The effect of copper concentration on the growth of oats is 

 very clearly demonstrated by Piper's photograph of his cultures 

 reproduced in Fig. 12. 



Piper's work has confirmed the view that reclamation disease 

 in oats is the result of copper deficiency. Similar experiments by 

 Piper on other members of the Gramineae, namely, wheat, 

 Lolium subulatum and Phalaris tuber osa, showed that these also 

 are affected in the same way by shortage of copper. 



5. The Symptoms of Molybdenum Deficiency 



The symptoms ascribable to molybdenum deficiency displayed 

 by tomato plants in water culture as described by Arnon and 

 Stout (1939) are these. First the lower leaves develop a very 

 characteristic mottling. This is followed later by necrosis at the 

 leaf margins along with a characteristic curving ever of the 

 marginal regions of the leaf. Abscission of flowers takes place so 

 that no fruit is produced. 



The symptoms of molybdenum deficiency of oats grown in 

 water culture are described by Piper (1940). About the time of 

 emergence of the panicles necrotic areas appear about midway 

 along the lamina of the upper leaves, and these areas frequently 

 extend right across the leaf. With a line of weakness so produced 

 the leaf bends back sharply; the band is first smooth, but 

 finally a kink develops and the middle necrotic region of the 

 leaf dries out a light reddish brown. Although the inflorescence 

 develops normally the grain consists entirely of empty husks. 



So far there is no record of molybdenum deficiency occurring 

 in plants in the field. 



