51 



VIRUSES AS ORGANISMS 



.6 

 .4- 



' Beale, Tobacco ynosaic. 

 " HUiiu^ell, Aucuba moiaic 



• 3a.Ui, Tbnuzto streak 



• Bold, Aucuha mosaic. 



• Bald. Tobacco mosaic. 



-1 



log ix) + log (vn) 



FIGURE 4-0 - EXPERIMENTAL PROBABILITY OF INFECTION OF 

 F. GLUTINOSA WITH TOBACCO MOSAIC VIRUS PLOTTED AS A 

 FUNCTION OF LOG]_o VIRUS CONCENTRATION. SOLID LINE IS 

 IDENTICAL WITH SOLID LINE IN FIGURE 3?. (K.A.Lauffer 

 and ^.C .Price, Arch. Biocheni. 8, 449 (194?; j. 



The solid curve fitting the data Is the graph of 

 babillty theory for the assumption that only one 

 cause infection. The broken curve which does no 

 the equation derived for the assumption that at 

 needed to cause an infection. It is clear that 

 one particle better than that of more than one. 

 are available. Price studied tobacco ringspot v 

 bean mosaic virus on the common bean. Chester s 

 on cowpeas, and Bald studied potato X virus on N 

 are presented in Figure 41, 



the equation derived from pro- 

 virus particle is needed to 

 t fit the data is the graph of 

 least two virus particles are 

 the data fit the equation for 

 Further data on plant viruses 

 iruB on cowpeas and southern 

 tudled cucumber mosaic virus 

 glutinosa . All of these data 



o " Price. Tobacco ririgspot. 

 • - Chaster Cuiumher Tiuuaic 

 o - Bald. PotaU) X 

 'a - Price, Southern bean mosaic. 



-\ 



FIGURE 41 - EXPERIMENTAL PROBABILITY OF INFECTION n'lTH VARIOUS 

 PLANT VIRUS-HOST SYSTEMS PLOTTED AS A FUNCTION OF LOG^o VIRUS 

 CONCENTRATION. SOLID LINE IS IDENTICAL WITH SOLID LINE IN FIGURE 

 37. (M.A. lauffer and W.C. Price, Arch. Biochem. 8, 449 (^9^5) }. 



In this case too the data are seen to fit the graph of the equation derived on 

 the asBximption that one virus particle can cause an infection if it happens to 

 be favorably situated. This does not mean at all that one lesion will be pro- 

 duced on the surface of a leaf for every virus particle in the solution rubbed 

 across the surface of that leaf, 'i'he rubbing spreads a film of an unknown 

 amount of virus solution and causes numerous minute injuries. The data mean 

 that it Is necessary for only one virus particle to come into contact with a 

 suitable injured region on the surface of the leaf. 



