10 Nov., 1916. J Foisoiiintj Effect of the "Johnson Grass." 653 



NOTE ON THE POISONING EFFECT OF THE " JOHNSON GRASS," 

 SORGHUM HALEPENSE. 



Bulletin of Miscellaneous Informaiion, Royal Botanic Gardens, 



Kew, England. 



Some recent correspondence in the Indian Forester, vol. xxxix., 

 ISTos. 6 and 10, upon the value of Sorghum halepense, as a fodder grass, 

 and the danger to cattle and horses which its use entails, shows that the 

 exact nature and reactions of the dangerous constituent are not well 

 understood. There is conclusive evidence that the young vegetative parts 

 of S. halepense are, under certain conditions, poisonous to farm animals, 

 and as the plant is, after rice, probably the commonest food and fodder 

 plant in India, besides being much used elsewhere, it has been deemed 

 desirable to publish a short note dealing with the matter. 



In 1902 Dunstan and Henry (Phil. Trans. Roy. See, A. 199, p. 399) 

 isolated a glucoside, which they called " dhurrin," from the leaves of the 

 great millet (tSorghuni vulgare). This substance was found to have the 

 empirical formula 0,^11^0. N, and on hydrolysis with hot dilute 

 hydrocliloric acid of the enzyme emulsin, yielded one molecule each of 

 prussic acid, parahydroxybcnzaldehyde, and dextrose. 



Sorgluim halei>ense, Pers. (Andropogon halepensis) is considered by 

 Hackel to ])e a variety of S. vulgare, Pers. {Andropogon sorgJimn), and 

 there is little doubt that " dhurrin " is found in it as well as in the 

 typical plant. The free prussic acid is the actual substance which causes 

 the death of animals eating the young vegetative parts of sorghum. 



The enzyme emulsin is present in the parts of the plant containing 

 the glucoside, and when in the early processes of digestion the tAvo come 

 together, the emulsin, by the addition of water to the " dhurrin," breaks 

 the latter down and liberates the poisonous prussic acid. 



An examination of the numerous records of cases in which sorghum 

 Vv'as used for fodder establishes two facts of practical importance. 



Firstly, the young vegetative parts of the plant are the most dangerous 

 to stock, the mature \)\iu\t being nearly or quite harmless. Analyses of 

 old plants have shown that little or no prussic acid yielding substance 

 was present. 



Secondly, the poisonous effect of the grass is enhanci'd in times of 

 drought. One writer states that the grass is dangerous only in the green 

 state, and that if the same grass is cut and dried and used as fodder, it 

 has no injurious effect. This may be due to the destruction of the 

 glucoside or the emulsin, or both, by the drying of the grass without 

 their coming into contact witli each other, but it is possible that the grass 

 was not cut till near maturity — that is to say, after tlu' disappearance of 

 tbe prussic acid yielding glucoside. 



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