Stabilization of purified potato virus X by dextran T-10 during lyophilization

Purification and preservation of potato virus X from leaf sap of tobacco plants before lyophilization was carried out by two methods: 1) precipitation by polyethylene glycol and ultracentifugation, and 2) precipitation by ammonium sulphate, chromatography on Sephadex G-50 and ultracentrifugation. The first method is preferable to the second because the final preparation contains more virus antigen. Both preparations were strongly infectious and maintained antigenic properties after lyophilization. To achieve a more gentle course of lyophilization of virus preparations, addition of urotropine and dextran T-10 to the virus suspension, purified by the precipitation by polyethylene glycol-6000, was examined. Addition of urotropine was proved unsatisfactory, because only antigenic properties were maintained after lyophilization while the infectivity disappeared. But we can recommend addition of dextran T-10 up to a concentration of 6% to the preparation of virus antigen before lyophilization. The course of lyophilization is much rapider, the lyophilized product can be very easily dissolved in water and is not hygroscopic. The product is strongly infectious and gives the serological precipitation reaction in a dilution four times that of X virus antigen lyophilized without addition of dextran T-10.     

Influence of light and darkness on the concentration of lactic,glycolic, succinic,malic and citric acid in pea plants

Chromatographic separation of an extract of organic acids on a Dowex-l column in the formiate cycle was used to study the content of several organic acids in pea plants, cultivated either in light or in darkness. Concentration changes of the individual acids in the course of growth indicate that the citrate cycle is blocked in the cotyledons of plants grown in light in the period around the 15th day of growth, probably at the site of succinic dehydrogenase (succinic and lactic acids accumulate and the content of citric and malic acids is exhausted). There is no inhibition in the cotyledons of etiolated plants. In vegetative organs, the concentration of the majority of the acids studied is lower than in cotyledons, probably because synthetic processes prevail over degradation processes in these organs. It seems that other processes besides the citrate cycle participate in malate synthesis in pea plants.     

Some properties of pea enation mosaic virus isolated from field pea and broad bean plants in Bohemia

Pea enation mosaic virus (PEMV) was isolated from disea sed field pea (Pisum sativum L.ssp. arvense A.Gr.) and broad bean (Faba vulgaris Moench) plants grown as filed crops at Bohumilice in Bohemia. The virus proved to be pathogenic for the following plant species:Pisum sativum L. cv. Raman,Faba vulgaris Moench,Lens culinaris Med.,Vicia sativa L.,Lathyrus odoratus L.,Glycine soja L.,Phaseolus vulgaris L.,Chenopodium amaranticolor Coste andReyn,Nicotiana clevelandi Gray,Trifolium incarnatum L. The dilution end point of the isolate was higher in pea plants (10^?4) than in broad bean plants (10^?2). The thermal inactivation point was 65–68° and the longevityin vitro between 10 and 14 days. According to the host range, symptoms on pea plants and physical properties the virus isolate studied resembles some isolates described in the U.S.A. and represents a PEMV strain different from those reported so far in Czechoslovakia.     

The dependence of the frequency of recessive lethal and vital mutations inArabidopsis thaliana (L.)Heynh. on the concentration of N-nitroso-N-methylurea

The dependence of the frequency of recessive lethal (two groups), chlorophyll and morphological mutations on the mutagen concentration was determined in M₂ after subjection to N-nitroso-N-methylurea applied to seeds ofArabidopsis in three concentrations (0·05, 0·10 and 0·20mm). The observed frequencies were compared with the theoretically expected ones for the linear and for two exponential types of dependence, by using the t-test, according to the formulas m=k. C, m=k. C^3/2, m=k. C². No satisfactory agreement with any expected type of dependence was found when directly observed frequencies were used. Since a considerable deficit of mutation frequency was observed in high concentrations, the correction of frequency values was done with respect to the probability of occurence of double mutations. After such a correction, a clear exponential relation was found in both types of lethals and a linear one in chlorophyll and morphological mutations. The probable occurence of multiple mutations should be, therefore, taken into account if the dependence of mutation frequency on the concentration of mutagen is discussed.