Kasvua hillitsevien aineiden vaikutus pavun taimien kasvuun II. Vaikutuksen riippuvuus yölämpötilasta ja kasvualustasta

Authors

• Erkki Kaukovirta Helsingin yliopiston puutarhatieteen laitos, Viik

DOI: https://doi.org/10.23986/afsci.71722

Abstract

The influence of growing media, sand soil and peat, night temperatures of 10° C, 13° C and 18°C, and growth retardants B-nine, Cycocel and Phosfon, on the growth of bean, Phascolus vulgaris var. vulgaris ’Juli’, was studied in artificial light. Three experiments were carried out in growth chambers equipped with 22 »Cool white» 80W-fluorescent tubes providing a light intensity of 5000 lux at plant level. The duration of the light period was 14 hours at a temperature of 20—22° C. The seeds were pregerminated at 25° C and grown in 4' plastic pots at 18° C night and 20—22° C day initial temperatures. When the primary leaves were fully opened the plants were treated with growth retardants and subjected to experimental night temperatures. The amount of Cycocel and B-nine in the treatments was 0.1 g, and that of Phosfon 0.015 g of active compound per pot, two seedlings per pot. The pots were irrigated by modified (WENT 1957) Hoagland solution (0.02 %) daily and if additional watering was needed, deionised water was used. Ten days after the application of retardants, the stem length, leaf area (by optical leaf planimeter) and the fresh and dry weights were measured. The results are given in Tables 1—4 and in Figure 1 as the averages of three experiments. B-nine, Cycocel and Phosfon retarded the stem growth regardless of other treatments, but the rate of retardation was dependent on the medium and the night temperatures. The percentage of retardation caused by B-nine and Phosfon was greatest in sand and by Cycocel in peat. In peat the effect of Phosfon on stem elongation was 2—3 times smaller than in sand. The biggest differences in the percentages of retardation between the different night temperatures were in B-nine treatments, 11 %, in Cycocel treatments, 13 %, and in Phosfon treatments, 23 %. The corresponding differences between different media were in B-nine treatments 23 %, in Cycocel treatments 37 %, and 60 % in Phosfon treatments. The percentage of stem retardation caused by Phosfon was highest in all the media at the night temperature in which the growth of the check plants was most vigorous. Similar trends were observed in seedlings treated with Cycocel, though it was not as clear as in the Phosfon treatments. B-nine and Cycocel did not affect significantly the growth of leaves and the accumulation of fresh weight of the whole plant, but B-nine decreased the dry weight of plants grown in sand at 10° C and Cycocel that of plants grown in sand at 10° C and 13° C and in peat at 18°C. B-nine increased the fresh weight of leaves in peat. Phosfon decreased significantly the area of leaves, and the fresh and dry weights of plants grown in sand, but increased the fresh weight of leaves and the dry weights of plants grown in peat. Also the area of leaves and the fresh weight of whole plants grown in peat was increased by Phosfon though this was not significant at all temperatures.