66 TRACE ELEMENT DEFICIENCY 



Table III. Manganese content of healthy and marsh 

 spotted peas. (Data from Glasscock and Wain) 



Manganese content in p. p.m. 



^i 



Part of seed Healthy seed Diseased seed 



Germ 15 3 



Cotyledon outer tissue 11 5 



Cotyledon centre tissue 6 < 2 



Seed coat 4 2 



The relationship of marsh spot to manganese deficiency was 

 definitely established by Piper (1941) by means of carefully 

 controlled water-culture experiments in which specially purified 

 media and carefully regulated amounts of manganese were used. 

 In addition to the ordinary major mineral nutrients the culture 

 solution contained small amounts of boron, copper, zinc and 

 molybdenum as well as sodium chloride. One series of peas was 

 grown in this culture solution without manganese, to four other 

 series 5, 10, 20 and 500/xg. manganese per litre were respec- 

 tively added. For the first 39 days after the seeds were put to 

 germinate no differences were observable in the various cultures, 

 but then in the manganese -free cultures there appeared mottling 

 of the younger leaves and brown lesions on the internodes and 

 tendrils. In a further 2-3 weeks growth stopped. 



In the cultures supplied with 5/xg. of manganese per litre 

 these same symptoms appeared, but not until 8 weeks from the 

 beginning of germination. On renewal of the solution, including 

 the manganese, healthy new growth was resumed, but in a 

 fortnight the same pathological symptoms again appeared. The 

 cultures produced a few flowers, but no fruits formed. 



The cultures supplied with 10/xg. of manganese per litre 

 showed no unfavourable symptoms after 8 weeks, apart from 

 slight mottling of the upper leaves, and after renewal of the 

 culture solution growth was vigorous and moderate flowering 

 took place. After another 3-4 weeks, however, the symptoms 

 of manganese deficiency appeared, and although some fruits 

 formed only a few ripened and these were small and imperfectly 

 developed, while the seeds they contained were all badly 

 affected with marsh spot. 



The cultures supplied with 20/xg. of manganese per litre grew 

 normally, flowered freely and produced numerous fruits with a 



