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    The photoperiod, this is used as a signal for the plant to flower. 

    Many flowering plants (angiosperms) use a photoreceptor protein, such as phytochrome or cryptochrome, to sense seasonal changes in night length, The Phytochrome conversion (Pfr to Pr) allows the plant to sense when it is night or day.

    Phytochrome Conversion

    The biologically-inactive form of phytochrome (Pr) is converted to the biologically-active form Pfr my the illumination with red light (mainly 660nm). Far-red (630nm) light and darkness convert the molecule back to the inactive form.

    What is the right light intensity and illumination length? Phytochrome Conversion 1

    Long Day Plant - LDP

    These plants flower when the days are longer. They require more than the critical duration of light to flower (usually 14-18 hours). They are also called ‘Short Night Plants’.

    Examples:  spinach, radish, hibiscus, Wheat, Lettuce,…

    Short Day Plant - SDP

    These plants flower when the days are shorterThey need less than the critical duration of light (about 8-12 hours) and a continuous dark period (about 14-16 hours) to flower. A continuous dark period is very critical for SDP plants. They are also called ‘Long Night Plants’.

    Examples: soybean, tobacco, chrysanthemum, cannabis Sativa L. etc.

    Neutral Day Plant - NDP

    These plants do not have critical daylength. Therefore, they are ‘neutral’ to the length of day or night. The Term: Automatic and automatic-flowering plants have established

    In other words, 
    Examples:  tomatoes, pea plants, rose, cannabis ruderalis,…

    Light intensity

    The current daylength (length of illumination) controls, depending on the plant’s type: (SDP, LDP, NDP) which growing-phase is currently initiated

    As a simplified version we usually differentiate between the following phases for a short day plant:

    • Germination (Sprouting) / Cuttings
    • Vegetative (Growing)
    • Generative (Flowering / Blooming)
    • Harvest (Finished)
    Based on the plant’s natural habitat, They require a different light intensity in each growing phase for optimal plant development.
    The required light intensity is different from plant to plant.
    Plant / Species Seedling / Cutting Vegetative Generative
    Tomatoe / Cucumber
    Orchids - Low Intensity (Phalaenopsis, Paphioedilum)
    Orchids - Medium Intensity (Brassia)
    Orchids - HIGH Intensity (Cattleya, Vanilla Bean, Vanda)

    Please note that the sunlight is a perfect full-spectrum light. Therefore Light intensities using artificial lighting are depending on the spectrum. The possible light intensities are usually lower.

    Growing Phases

    Plant growing phases
    Plant growing phases

    Light or CO2 limited?

    Light or CO2 limited?

    Plants require beside Water and Light a variety of so-called Macro (N,P,K) and Mico nutrients. During photosynthesis uses light energy to convert water, carbon dioxide (CO2), and minerals into oxygen and energy-rich organic compounds. Depending on the light intensity each part like macronutrients (N, P, K) and micronutrient can lead to limitations in growth and development. While most Substances can be applied quite easily, carbon dioxide has a special role.

    The natural Level ranges from 400 to 450 parts per million (ppm) of the earth’s atmosphere.
    Low light intensities can limit plant growth, at a certain point Co2 becomes the most limiting factor and supplemental CO2 can be required to achieve further increase.

    The point where it requires is depending on the plant species and genotype as well as the required amount of artificial Co2 is depending on numerous factors.


    DLI - Daily Light Integral.

    DLI  – describes the delivered amount of light in a 24h period.

    PPFD x Time = DLI [mol/m²d]

    It is possible to increase the amount of light (DLI) by increasing the illumintation period. It is important to stay in the required photoperiod (long / short day period)


    Daily Light Integral – DLI – [mol/m²d]

    Daily Light Integral Daily light integral (DLI) describes the number of photosynthetically active photons (individual particles of light in the 400-700 nm range, PAR) that are delivered
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