The growth factors - the light - part 3

Stunted growth and the complete lack of formation of new shoots indicate a lack of light. Usually you will find out, that even with perfectly healthy plants in the seasons with little light, new shoots that have arisen remain much smaller than those that have grown at normal times. The greatly reduced influence of light is the only cause. This phenomenon can also be observed in many other tropical plants. Stunted growth and the complete lack of formation of new shoots indicate a lack of light. Usually you will find out, that even with perfectly healthy plants in the seasons with little light, new shoots that have arisen remain much smaller than those that have grown at normal times. The greatly reduced influence of light is the only cause. This phenomenon can also be observed in many other tropical plants.
The possibility, to compensate for insufficient daylight through additional artificial lighting in the months with little light, is getting more and more attention. Due to the artificial light, genera and species that are more difficult to keep are also included in room maintenance. The possible increase in assimilation and the resulting increased promotion of growth depend on the strength of the exposure and its duration.
In view of the very expensive test material – as it is represented by orchids – relatively little is known about their needs and their behavior in the event of additional artificial light irradiation.
According to Schoser (see references) the following values ​​are indicative:

Cattlaya and relatives:
after germination 2000 lx 16 h/d
after pricking 4000 lx 16 h/d
im 4 cm pot 6000-15000 lx 16 h/d
im 8 cm pot 15 000-25 000 lx 16 h/d
Large plants bloom as they increase 45000 Lux for the first time in about 2½ years instead of in 7 Years.

Cymbidium
Seedlings 8000 lx 16 h/d
old plants 15 000 lx 16 h/d

Odontoglossum crispum and hybrids
Seedlings 8000 lx 16 h/d
old plants 15000 lx 16 h/d

Paphiopedilum
Seedlings 2500 lx 16 h/d
flowering plants 7500 lx 16 h/d

Phalaenopsis
Seedlings 1000 lx 12 h/d
flowering plants 7500 lx 9 h/d
lx = Lux, h / d = Hours per day

The values ​​are roughly in the range of 1000-10000 lx. This corresponds to a lamp power to be installed of 40 to 400 Watt per square meter = W / m. In winter, intensive additional light is appropriate for all orchids from October to March. Beyond this period, only intensive cultures of young plants in relation to the duration of daylight are to be additionally exposed with a prospect of success ; daylight is sufficient for larger and fully grown plants, if sufficiently available, out.
The transfer of the values ​​listed above to the conditions of the orchid friend is generally not possible, because local conditions can be very different. With almost normal site conditions – thus sufficient exposure to daylight – are about 100 Watt per square meter is sufficient. In poor lighting conditions – about showcases in the room – are about 200 Watts per square meter for a duration of 16 Hours required.
Overall, only fluorescent tubes can be considered for the additional exposure. The relatively higher installation costs are offset by the high light output and the low power consumption, as well as the average 7500 Burning hours denoted long service life. The blue and light red-dark red areas of the spectrum are of decisive importance for plant growth. On it are those commercially available - specially developed to promote the growth of plants – Tube types aligned. Their radiation corresponds to the spectrum of activity of chlorophyll synthesis. The successes achieved so far speak clearly in favor of their application. When used in the room, the blue-red light can be a bit disturbing. Mixed light is then recommended, thus a coupling with daylight- or warm tone tubes.

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