GROWTH ACCELERATION, IMPROVING OF QUALITY AND TIMING OF FLOWERING BY INFLUENCING TEMPERATURE AND LIGHT

W. Rünger
Growth acceleration shortens the duration of the culture, while improved quality raises the value of our products, and timing of flowering improves the sale, increases the economical value of the greenhouses, even shortening the growing-time in some cases. Improving these matters will lead to improved productivity and a higher profitability.

The ways of attaining these goals are manifold. However, the issue is very complicated by the variations in response among species, and even varieties. As for pot plants our knowledge is far too inadequate. Obviously more detailed data are needed.

Growth accelerates, as both temperature and light intensity approach their optimum. Using the available data, we can direct our efforts towards optimum environmental conditions. In doing so, however, we should bear in mind the economical aspects, particularly the law of diminishing returns.

Our knowledge about pot plants is small in relation to other ornamentals, particularly when considering, that the optimum conditions vary with plants development and season, and that interactions with other factors exist. Admittedly practical experience is still the base of the culture for most pot plants. However, not only do we try to get the optimum temperature and as much light as possible for the plants, but we can also accelerate the growth by influencing the development in the right phase. We know little about this, but in such a case often a considerable growth acceleration is possible at little expense. I will show that with Kalanchoe as an example.

Kalanchoe has a juvenile phase varying in length among the varieties (6). In plants that have exceeded this phase, long days are necessary to prevent flowering. Though this does not hold for the juvenile phase, yet the day length seems to exert an influence on the plants (5, 6). In Figures 1 and 2 with short days the internodes are short, the leaves more succulent and in most varieties the leaves are smaller than with long days. According to the variety, the differences in the shape between short day and long day samples are not alike.

If the plants get long days after the juvenile phase, the plants grow vegetatively and the new leaves have the shape, that is typical of long day conditions. Plants that have had short days in the juvenile phase show the same response. However, these plants exhibit a lower rate of growth compared to plants with long days in the juvenile phase (Table 1), although at the end of the different treatments no difference exists between short-long-day samples, or even a difference in favour to the short day ones can be found, as we can see in table 2. This phenomenon exists

Rünger, W. (1973). GROWTH ACCELERATION, IMPROVING OF QUALITY AND TIMING OF FLOWERING BY INFLUENCING TEMPERATURE AND LIGHT. Acta Hortic. 31, 17-26
DOI: 10.17660/ActaHortic.1973.31.2
https://doi.org/10.17660/ActaHortic.1973.31.2

Acta Horticulturae