Asmaa Sayed AHMED 1, Arshad Abdulkhalq YASEEN 1,2*, Triska Dlshad BAKR 1,3
1 Department of Horticulture, College of Agricultural Engineering Sciences, Salahaddin University-Erbil, 44002 Kurdistan Region, Iraq
2 Institute of Horticultural Sciences, Faculty of the Agricultural and Food Sciences and Environmental Management, University of Debrecen, H-4032 Debrecen, Böszörményi Street 138
3 Khabat Technical Institute, Department of Horticulture, Erbil Polytechnic University, Erbil, Kurdistan Region, Iraq

The use of light-emitting diodes (LEDs) is a recent concerned application in the indoor crop system of the modern plant production. In our research, we evaluated the influence of four monochromic LED lights including 100% White (W), Yellow (Y), Red (R) and Blue (B) in comparison to solar lightening condition (GR) as a control. In this regard, some morphological characteristics and biochemical content of the common outdoor ‘Iceberg’ lettuce (Lactuca sativa L.) was measured. The results show that leaf length, leaf area and total head weight were significantly greater in the plants grown under B LED, while all the other physical parameters were significantly higher in the plants grown under GR environmental conditions. On the other hand, chlorophyll (Chl), carotenoids (Car), and nitrate content were also influenced by different light treatments. Plants grown under LED light treatment resulted in significantly higher chlorophyll content compared to the control. However, significantly greater carotenoid content was in the plants grown under GR condition. The highest total chlorophyll content was recorded under B and R LED, whereas the lowest was in the GR condition. The lowest nitrate content in the blade and petiole was recorded in the plants grown under Y LED, while the highest nitrate content was recorded in the GR. Based on our result, it is possible to grow and improve some quality parameters of common outdoor ‘iceberg’ lettuce under LED where the solar light is limited or unavailable. Thus, plants performed better under GR light conditions than monochromic LEDs; however, some LED lights could improve some quality parameters and biochemical contents in the ‘iceberg’ lettuce variety.