62 TRACE ELEMENT DEFICIENCY 



apex of the leaves, but with very irregular margins. In type B 

 the streaks are also continuous throughout the leaf but have very 

 regular margins and occupy the whole intervenal region. In 

 the type attributable to manganese deficiency, on the other 

 hand, the chlorotic areas form discontinuous spots or stripes. 

 White or chlorotic spots first appeared in the cultures when 

 these were about 3 weeks old. As the leaves grew the spots also 

 increased in area, and as the affection became more severe the 

 spots tended to coalesce into elongated chlorotic streaks. The 

 tissue in the middle of the chlorotic areas then turned brown, 

 broke down and was dead. Sometimes the dead tissue fell out 

 of the leaf, leaving a number of holes. The similarity of the con- 

 dition to grey stripe of oats is striking, and a photograph of 

 maize leaves affected by their type C chlorosis published by 

 Pettinger, Henderson and Wingard bears a close resemblance 

 to that of oat leaves affected by grey stripe reproduced in Fig. 2. 



Pahala Blight of Sugar Cane. The disease of sugar cane 

 named Pahala blight, after a small town in Hawaii where it was 

 first observed, is characterized by a partial chlorosis of the 

 leaves, the chlorotic areas taking the form of long white streaks. 

 These are limited to the leaf blades and do not occur on the leaf 

 sheaths. The third, fourth and fifth youngest leaves are generally 

 those most affected. As the chlorotic cells die red spots appear, 

 and as these increase in number neighbouring spots may coalesce 

 so that continuous red streaks result, and there may then follow 

 splitting of the leaf along the line of the streak. By the time 

 red spots appear the plant is generally very much stunted. 

 A fungus, Mycosphaerella striatiformans, frequently appears on 

 the red spots, and when the disease was first described in 1906 

 it was attributed to the attack of this fungus, but in 1928 Lee 

 and McHargue produced evidence that the Pahala blight results 

 from a deficiency of manganese, the fungal attack being secon- 

 dary to this. This conclusion is based on three lines of evidence 

 derived respectively from the results of the application of 

 solutions, and particularly powders, containing manganese 

 sulphate to the leaves, from chemical analyses of normal and 

 affected leaves, and from sand-culture experiments. 



As regards the effect of applying manganese sulphate to the 

 leaves it was found that this salt, generally applied as a dust with 



