- Supplementation of 730nm, 630, 660nm, ideal for Emerson effect and general lift in red content of total spectrum
SSK-1560-730+660: The PCB comes with Solderless Connectors, Board has 12 leds spaced on an even pitch for beautiful blending and maximum utilisation of the PCB real estate, Nominal 22.1* Volts at 700ma for 16.8 watt operation recommended drive current with minimal heat sinking. At 1amp, the board will be at 28.5volts and 28.5 watts, We recommend good quality thermal bed, Cooler or Aluminium Sheet* *based on 10 pcs of XPG-3 G bin bin at 700m
- 560mm x 25mm x 1.5mm, Aluminium Metal Core PCB
- LEDS Cree XP footprint for most powerful photons available
- Forward Voltage 28.5V nominal
- Drive Current typ 700ma, max 1500ma(XPG-3)
- typically board is made with 12 leds, but lower cost variants with less led’s available
End of Day
The R:FR ratio of direct sunlight is about 1.3 during most of the day, but it approaches 0.6 or so during twilight when the atmosphere preferentially scatters blue light and the sky turns yellow and red. This only lasts for half an hour or less, but it is important because plants use these changes to synchronize their internal circadian clocks both with the 24-hour day and the seasons. This involves a burst of gene expression activity that is controlled by phytochrome.
Blackout curtains can be used in greenhouses to eliminate twilight, and both red and far-red LEDs can be used to simulate twilight for vertical farms at the end of the daily photoperiod. Interestingly, low PAR values are required, on the order of one µmol·m-2·sec-1, for this purpose. Various SAS responses to red and far-red pulses have been recorded for different species, including stem elongation and changes in leaf area. End-of-day pulses of far-red radiation, for example, have been shown to result in useful hypocotyl elongation of tomato rootstocks for grafting.
On a clear day, direct sunlight has a ratio of red light to far-red radiation (R:FR) of about 1.3. That is, there is about 30 percent more red light than far-red radiation that is received by the plant leaves. Even daylight reflected from natural inorganic materials, such as rock and soil, exhibits roughly the same R:FR ratio.
When the direct sunlight is being blocked by the leaves of neighboring plants, however, the “red edge” effect takes hold. A single layer of leaves can change the R:FR ratio from 1.3 to 0.2 or less. That is, there is now about six times less red light than far-red radiation incident on the plant leaves. Two layers of leaves and the difference becomes 30 times or more.
Flowering plants use phytochrome to detect the R:FR ratio and so decide whether SAS responses are necessary. In addition to detecting whether the direct sunlight is being directly blocked, the plants can determine from the R:FR ratio whether there are neighboring plants that might pose a future threat and so initiate appropriate SAS responses.