Effect of Supplementary Cyan Light to Deep Red and Royal Blue Range Wavelengths on the Seedling Period of Iceberg Lettuces

摘要

In this article, effect of cyan (≈500 nm) light on the plant growth as a supplementary light source to common deep red (≈660 nm) and royal blue (≈440) lights is examined. For this purpose, a 4-floor shelf was prepared containing Vernalia type iceberg lettuce (Lactuca sativa) seeds. Carbon dioxide content of air, soil moisture, air humidity, environment temperature, water, pH, electrical conductivity, fertilizer and nutrient contents were controlled at desired values; being same for the whole system. Second and third floors were lighted 18 hours a day, with the same photosynthetic photon flux density (PPFD) of 360 μmol m -2 s -1 . Third floor’s lighting was composed of 65% deep red and 35% royal blue lights. Second floor’s lighting was composed of 55% deep red, 25% royal blue and 20% cyan lights. First floor was lighted with sunlight, in order to make a comparison with natural lighting. Fourth floor contained the necessary control equipment. The experiment lasted for 15 days to analyse only the seedling period. The experiment results showed that, addition of cyan light to conventional red and blue grow lightings allowed the plants to grow 14% more by stem system. Also, cyan light provided a stronger root development and higher leaf area; which would indicate a higher product yield in the vegetative period.