Pitkäaaltoisen uv-valon sekä kasvunsääteiden vaikutus krysanteemin kasvuun

Authors

• Erkki Kaukovirta Helsingin yliopiston puutarhatieteen laitos

DOI: https://doi.org/10.23986/afsci.71701

Abstract

Natural daylight conditions in Finland vary considerably during summer and winter months, not only as regards the amount but also the quality of light. The proportion of radiation with short wave bands to total radiation is lower in winter than in summer owing to the leight of the sun. For example, when the elevation of the sun is 50° the amount of near UV-light is 95.4 % of its average maximum but when the elevation of the sun is 15° the corresponding figure is 2.9 % (LUNELUND 1936 and 1945). Little attention has been paid to this variation in light quality in horticultural research in this country. A study of how this type of variation in the quality of light might affect the growth of horticultural crops therefore seemed justified. This paper is a report of experiments in which the effect of near UV-light on the growth of chrysanthemum has been studied. In the experiments (1965—1967) chrysanthemum cuttings were treated with Cycocel and Phosfon. Treated and untreated cuttings were subjected to near UV-supplementary light (see Fig. 1) both during light and dark periods. UV-supplementary light was given during 39 days starting from planting. Two of the experiments were carried out in natural light conditions and one under artificial light in growth cabinets equipped with 22 Philips TLA 80W/55 fluorescent tubes. The results are given in Tables 2—6 and in Figures 3 and 4. In each experiment the near UV was found to increase the stem elongation of chrysanthemum. This increase was due partly to the increased length of the internodes. The effect of UV-light was greatest on plants not treated with growth retardants and more pronounced in plants treated with Cycocel than in plants treated with Phosfon. The UV-light given during dark periods resulted in higher plants than UV given during light periods. The UV-supplementary light did not have any photoperiodic effect and no harmful effect other than the stem elongation was observed.