90 trace element deficiency 



4. Diseases Attributable to a 

 Deficiency of Copper 



Although copper has now been shown to be essential for the 

 growth of a number of plants, diseases attributable to a shortage 

 of this element are rarely met with in the field and none are 

 known to occur in Britain. The two well-recognized diseases 

 which appear to be related to copper shortage are an affection 

 of fruit trees known as exanthema, die-back or chlorosis, and a 

 disease of various herbaceous plants known as reclamation 

 disease. These are described later. 



The general effects of copper deficiency on the leaves of 

 tomato plants have been described by Reed (1939). The leaves 

 exhibit restricted growth, but although they are considerably 

 smaller than normal leaves the number of leaflets and lobes of 

 the leaflets is not reduced. The laminae of the leaflets are in- 

 curved and they develop a bluish green colour with a distinct 

 sheen. Later necrotic areas appear. 



Microscopic examination showed that in the early stages of 

 development the palisade cells of affected leaves contained 

 many large hyper chromatic plastids. These plastids ulti- 

 mately degenerate, at the same time tending to form aggrega- 

 tions at one end of the cell. Cavities tend to form below stomata 

 by the separation of the upper ends of adjacent palisade cells. 

 The cavity may lengthen so that ultimately it extends the 

 whole length of the cells and at the same time broadens owing 

 to the shrinkage of the cells, this being followed by a disappear- 

 ance of the cells owing to lysis of their contents. These processes 

 appear to lead to the production of the necrotic areas already 

 mentioned. 



Exanthema or Die -back of Fruit Trees. A pathological 

 condition known as exanthema affects various fruit trees in- 

 cluding both Citrus species and rosaceous trees as well as the 

 olive. The disease was recorded in Citrus in Florida in 1875, but 

 it was not described for other trees until 1928, when Smith and 

 Thomas recorded that for a long time it had been known in 

 California as affecting other fruit trees. They reported it as 

 occurring in French prune, Japanese plum, apple, pear and 

 olive trees. 



