PLANT DISEASES 



DISEASES NOT DUE TO PARASITES 

 OR OF UNKNO^\rN ORIGIN. 



1027 - Researches as to Injuries caused by Lighting-gas to Plants. — .sokauer Paul., in 



Zcitschrift fur Pflanzenkrankheitcn, Vol. 26, No. 3-1, pp. 129-183. Stuttgart, June i, 1916. 



At the request of the Berlin Gas Works the writer made experiments, 

 the results of which are set out in the present work, on the damage caused 

 to plants by lighting-gas. These experiments were conducted in the large 

 parks of Berlin, which proved well adapted for the purpose. 



The writer proposed in the first place to ascertain by experiment the 

 character of the toxic effects due to lighting-gas. Hitherto the blue colour- 

 ing of the roots was regarded as a satisfactory indication, but these experi- 

 ments have made it clear that this phenomenon often gives a misleading 

 result. Sy.stematic experiments were begun in the spring of 1913, with 

 Primus Padus ,Ulmus scnhra, Carpinus Betnlus, Viburnum Opulus, Qitercus 

 pedunculata, Ulmus campestris, Urtica dioica, Syringa mdgaris and a large 

 number of ornamental plants. 



In all plants suffering with gas poisoning it was observed in the first 

 place that the chlorophyll was attacked, disappearing little by little. The 

 process of assimilation and the formation of new organic substances, in 

 spite of the presence of all factors of growth, are impeded in soil permeated 

 with lighting-gas, and the plant utilises its own substance for intramole- 

 cular respiration. These phenomena indicate the existence of a process 

 of asphyxia through the want of oxygen in the roots. If lighting-gas eft"ec- 

 tively acts on the roots, the consequence of intramolecular respiration also 

 appears on the overground parts of the plant. That is why those parts of 

 the leaf which receive the least sap (edges of the leaf) are the first to show dis- 

 coloration or disappearance of the chlorophyll, and also why the first signs 

 of withering (appearance of dry spots and edgings) appear on the edges 

 of the leaf. 



With the drying of the periphery of the green organs, and the reduction 

 of evaporation, an excess of water is observed as a consequence in the lower 

 parts of the stalk and roots of the plant. This phenomenon is noticed at 



