Der Einfluß von Infektionen mit dem Kartoffel‐X‐Virus und Behandlung mit der antiphytoviralen Substanz 2,4‐Dioxohexahydro‐1,3,5‐triazin auf die Bildung und den Apikaltransport 14C‐markierter Assimilate und die Konzentration freier Aminosäuren

Abstract

Abstract The influence of infections with potato virus X and treatment with the antiphytoviral substance 2,4‐dioxohexahydro‐1,3,5‐triazine on the formation and the apical transport of 14C‐labeled assimilates and on the concentration of free amino acids After two hours of exposure of lower leaves of Nicotiana tabacum L. 'Samsun’to an air containing 15.91 MBq 14CO2 per liter of air, the bulk of the activity of assimilated 14CO2 was found in glucose. Lower activities at different RF values were obviously assignable to intermediates of photosynthesis. Saccharose was not labeled. Infections with potato virus X (PVX) resulted in the incorporation of 14CO2 into the assimilates being reduced by about 28 %, but the relative proportion of apically transported labeled assimilates in virus‐infected plants was only insignificantly diminished compared with that in healthy plants. Treatment with the antiphytoviral compound 2,4‐dioxohexahydro‐1,3,5‐ triazine (DHT = 5‐azadihydrouracil) had no appreciable effect upon 14CO2 incorporation of healthy plants. By contrast, 14CO2 incorporation into assimilates was greatly increased by DHT in the case of virus‐infected plants, now reaching values that exceeded those of healthy plants receiving no treatment. The main reason for this is seen in the great reduction in the concentration of PVX and, consequently, in the virus‐induced reduction of photosynthesis. Apical transport of assimilates from exposed leaves was substantially reduced, after treatment with DHT, in healthy as well as in virus‐infected plants. Obviously, the afraction of by older leaves exposed to 14CO2 has been increased by cytoKinin activities of DHT to such an extent that the source‐to‐sink conditions influencing the intensity of phloem transport have been substantially changed. The pattern of detected free ammino acids had, in the leaves exposed to 14CO2 been expanded, after infection with PVX, by histidine and phenylalanine. In the apical leaves, in which a larger number of free amino acids had been detected than in the lower leaves exposed to 14CO2, there was also observed an additional occurrence of phenylalanine in plants infected with PVX, whereas two not specified amino acids disappeared. Treatment with DHT did not change the amino acid pattern of healthy control plants. In plants infected with PVX, DHT had the effect of canceling virus‐induced variations in the amino acid pattern (one exception being phenylalanine in apically inserted leaves). Evidently, this was brought about indirectly by strong inhibition of virus replication and, consequently, by elimination of virus‐induced variations.