On the interaction of growth retardants with IAA and kinetin

In the pea test a highly positive response to the treatment with IAA reversed to a negative one or became 5 to 6 times weaker when CCC was applied together with IAA. In cultivating pea seedlings, following their decapitation, for two days in a 0.25 per cent CCC solution and then in water, growth of their cotyledonous axillaries (cotylaries) were inhibited. This inhibitive action of CCC could be made ineffective when the seedlings, following two-days’ cultivation in the CCC solution, were grown further in kinetin solutions (0.37–3 mg per 1). Cotylaries of decapitated pea seedlings, when grown in kinetin solutions were inhibited. With kinetin solutions of 6–12 mg/l a strong inhibition also occured in the growth of roots at the apical parts of which spherical swellings were developing. The CCC supplied to the roots of intact etiolated pea seedlings is translocated acropetally into the stem at a rate of about 5 cm per hour. Decapitation of the plant causes retardation of this transport, yet a coat of 0.00001–1% IAA or kinetin paste produces acceleration of the stream. Existence of an antagonism between CCC and IAA, demonstrated earlier, was found holding true also for B-9 (N, N-dimethyl-aminesuccinamic acid) and IAA, as the inhibitive action of B-9, 0.06% solution on the growth of lettuce hypocotyls was reduced to a highly significant degree when the plants were supplied with B-9 together with IAA at a concentration of 10 mg/l.     

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.     

UV sensitivity of germinating culture ofBacillus cereus

The spores ofBacillus cereus can be germinated in reasonable synchrony in rich media. The survival of germinating cells after UV irradiation is strongly affected by repair. When plating on mineral agar a linear decrease of survival is obtained between 20–60 min of germination, whereas the survival on nutrient agar shows only minor fluctuations. The difference in survival on these two media which reached 1–2 orders of magnitude is due mostly to the shape of the shoulder on the survival curve. Survival on mineral agar may be increased by postincubation in complex media or by preincubation in mineral media. It was concluded that repression and derepression of biosynthetic pathways was responsible for the different efficiency of repair.