GROWTH ASPECTS OF PLANT VIRUS INFECTIONS 647 



tion of temperature and closely parallels host growth. However, in 

 systemically-infected leaves, where movement and transport are in- 

 volved, the rate of virus accumulation is often inversely related to host 

 growth. In some host-virus combinations a cyclic pattern of virus con- 

 centration accompanies a straight-line pattern of growth. Initial virus 

 synthesis is also generally favored by long days and relatively high 

 light intensities— conditions which also favor host growth. In some 

 cases this relationship between virus synthesis and host growth con- 

 tinues with time, while in others no such correlation occurs. 



Thus there is considerable evidence that virus synthesis is closely 

 and directly related to the host growth processes. But virus accumula- 

 tion in plants, which depends upon movement of virus out of cells, 

 transport to other portions of the plant, and entry into cells, is a dif- 

 ferent story. It is probably here that explanations of the anamolous 

 situations described are to be found. 



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