Kasvua hillitsevien aineiden vaikutus pavun taimien kasvuun III. Vaikutuksen riippuvuus lämpötilasta

Authors

• Erkki Kaukovirta Helsingin yliopiston puutarhatieteen laitos

DOI: https://doi.org/10.23986/afsci.71737

Abstract

The relation of growth retardants B-nine, Cycocel and Phosfon in different temperatures to the growth of bean seedlings (Phaseolus vulgaris var. vulgaris ’July’) was studied in artificial and natural light. The experiments in artificial light were carried out in growth chambers (Sherer Cell 27-7HL) equipped with WHO 110 watt fluorescent tubes providing a light intensity of 14000 lux at plant level. The duration of the light period was 14 hours at temperatures of 24°, 21° or 18° C. The night temperature was 18° C in all treatments. The experiments in natural daylight were carried out in temperature controlled (± 0.5° C) greenhouses at the Agricultural College of Norway. The temperature treatments were as follows 1) constant day and night temperatures of 12°, 15°, 18°, 21°, 24° and 27°, 2) day temperature of 24° C with 12°, 15°, 18°, 21°, 24° and 27° C night temperatures and, 3) day temperature of 18° C with 12°, 15°, 18°, 21° and 24° C night temperatures. The duration of the night temperature was 14 hours and the daily duration of daylight was 14—13 hours. The seedlings were grown in sand in 4 inch plastic pots and at 21 ° C initial day and night temperature. When the primary leaves were fully open, the plants were treated with growth retardants and subjected to experimental temperatures. The amount of Cycocel and B-nine was 100/mg and that of Phosfon 15 mg per pot of three seedlings in the experiments in artificial light. In the trials in natural daylight, the following amounts of growth retardants were used: B-nine 375 mg, Cycocel 75 mg and Phosfon 6.2 mg of active compound per pot of three seedlings. The pots were irrigated by modified (WENT 1957) Hoagland solution (0.02 %) daily. The data were recorded 13 days after the treatments and the results are given in Tables 1—6 and in Figs. 1 —2. All compounds retarded the stem growth at all temperatures, but the ratrdation was not significant at the constant day and night temperature of 12° C. The intensity of retardation was dependent on the temperature. At constant day and night temperatures the differences in stem length between untreated plants and plants treated with B-nine and Phosfon increased rapidly with the rise of the temperature in temperature ranges of 12° C to 21 ° C. This was the case also with the plants treated with Cycocel in temperature ranges of 12° C to 18° C. Temperatures higher than those did not cause significant changes in the differences in stem length between untreated and treated plants. The intensity of stem retardation caused by Phosfon showed similar correlation to average day temperature regardless of the day and night temperatures. This was so also with Cycocel and B-nine providing the night temperature was not higher than the day temperature. When the night temperature was higher than the day temperature, the intensity of stem retardation caused by B-nine and Cycocel showed a tendency to decrease with the rise in the average daily temperature. The fresh and dry weights and the area of leaves were decreased by growth retardants though not at all temperatures. Differences in weight and area of leaves between untreated and treated plants did not show similar correlation to average day temperatures as did the retardation of stem elongation. The fresh weight of leaves was retarded most (30 %) by all retardants at day and night temperatures of 12° C, while that of whole plants was retarded by B-nine (39 %) and Phosfon (40 %) at day and night temperatures of 21° C and by Cycocel (39 %) at 24° day and 18 °C night temperature. The effect of growth retardants on the growth of bean seedlings was in general less pronounced in artificial light than in natural daylight, probably because of the differences in light conditions.