ISHS Acta Horticulturae 327: II European Workshop on Thermo- and Photomorphogenesis in Plants
PREFACE - SECOND EUROPEAN WORKSHOP ON THERMO- AND PHOTOMORPHOGENESIS IN PLANTS. |
| Authors: | R. Moe, Leiv M. Mortensen |
| Abstract:
This workshop was held at The Agricultural University of Norway, Ås, Norway 2–3 March 1992. It was organized by ISHS, Section Ornamental Plants, under supervision of a committee including Leiv M. Mortensen, Roar Moe and Idun Bratberg, Norway. Eighteen colleagues from seven countries participated in the meeting, and 14 papers were presented. The workshop was a follow-up of the first meeting in Aalsmeer, The Netherlands, in 1990. The objective of the workshop was to exchange results from recent experiments related to control of plant morphogenesis without the use of plant growth retardants. We want to thank all participants for their contributions through presentations and discussions, and we feel that the meeting gave a very valuable contribution to better to understand the potential of controlling plant morphogenesis particularly by temperature. The papers presented at the workshop will be published in a forthcoming ISSUE of Acta Horticulturae. We are very grateful to Dr. Allan Langton (UK) who has corrected the English and made many valuable comments to the authors. Thank you for a great job. We are looking forward to the next meeting in Hannover in September 1993, and hope that questions raised during the workshop at Ås can be answered then.
Meanwhile, we want to wish the different research groups good luck with the experimental studies.
Roar Moe The objective of this workshop was to discuss how plant morphogenesis could be controlled without the use of chemical growth retardants. As the title of the workshop indicates, this is done by temperature and light. The first workshop on this subject was held in the Netherlands in November 1990 (Acta Hortic. volume 305), and the present workshop was a follow-up of the discussions from that meeting. During the workshop 14 papers, based on recent research results, were presented. Nine of these discussed the influence of temperature on plant morphogenesis (thermomorphogenesis). Naturally, the most of the time was therefore used on thermomorphogenesis. It was interesting to compare the results from similar experiments in different countries, and generally it was a surprising accordance between the results from the different research groups. The effect of negative DIF (lower day than night temperature) and positive DIF (higher day than night temperature), and/or temperature drop before or after dawn was studied in a number of 17 species as included in nine research works. Negative DIF often gave shorter and positive DIF often longer plants as compared to constant temperature. However, it was interesting to note that some species was rather insensitive to these treatments. So generalizations are difficult to make with respect to DIF effects on plants. Some of the species (Euphorbia, Pelargonium, Petunia, Impatiens and Salvia) were investigated in at least three countries, and it was therefore of great interest to compare the results. The conclusions on how different temperature treatments affected Euphorbia pulcherrima were the same from Germany, Great Britain and Norway: Negative DIF gave shorter plants, positive DIF longer plants, and a temperature drop (-6°C) lasting a couple of hours before or after dawn was as effective as negative DIF. However, out of the 17 tested species it was only this species in addition to chrysanthemum that responded to a drop treatment. The bedding plants Pelargonium, Impatients, Petunia and Salvia were investigated in 5–6 different countries. The same plant material was used in three of the countries in a joint research work, and the results were very similar in all countries: No or only a very small effect by a 2-h temperature drop (-6°C) before or after dawn. This result was in accordance with the findings on the same species in a fourth country, while a 2-h drop (-6°C) starting at dawn in a fifth country was found to reduce the plant height in all these species except Pelargonium. In one single study 14 species were included, but none of the species responded to a 1.5-h temperature drop around dawn. However, the plants were grown in long days in this experiment, and there are indications that the effect of temperature drop is linked to short day treatments as was the case with poinsettia and chrysanthemum. Research is needed now to reveal possible relationships between temperature drop and the length of the photoperiod. Such investigation should be done with day neutral species. It might also be that the effect of DIF as well as temperature drop depends on the light level, CO2 concentration, air humidity and other growth factors. A systematic approach should be undertaken in order to be able to detect such relationships. It appears that temperature manipulations alone are not sufficient to control plant morphogenesis in many plant species. Light quality is known to affect shoot elongation and is therefore a potential means to control the morphogenesis. Only a few papers dealt with photomorphogenesis including a study with the use of UV-light, a study on day extension lighting with different light qualities to poinsettia, and a study on effects of light quality on the in vitro propagation of birch. Also an interesting paper was presented on the effect of supplementary lighting on the crops of neighbours in addition to a paper on the effect of water vapour deficit on plant morphogenesis. At the end of the workshop future research activities were discussed and it was an agreement upon working further with effects of DIF and temperature drop as influenced by photoperiod, light level, watering frequence, air humidity and other growth factors. The next workshop was decided to be held at the Lehr- and Versuchanstalt für Gartenbau Ahlem, Hannover, Germany. In order to include all factors affecting plant morphogenesis, the title of the working group was decided to be: "Environmental regulation of plant morphogenesis".
Roar Moe | |
