Document Type : Research paper
Authors
- Hossein Sheikhi 1
- Mojtaba Delshad 1
- Sasan Aliniaeifard 2
- Kamahldin Haghbeen 3
- Mesbah Bababalar 1
- Rasool Nasiri 1
1 Horticultural Sciences Department, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
2 Department of Horticulture, Faculty of Agricultural Technology, Aburaihan Campus, University of Tehran, Tehran, Iran
3 Department of Agricultural Biotechnology, National Institute for Genetic Engineering and Biotechnology, Tehran, Iran
Abstract
Lettuce is one of the most important leafy vegetable crops. Despite lettuce being mostly grown in open fields, its greenhouse production is widely increasing. Lettuce growth comprises two distinct stages known as the seedling and head stages. The effect of supplemental lighting (SL) on lettuce growth was well studied, but the lighting requirement during the early stage of its growth and head development remained unknown. For this purpose, we evaluated nutritional qualities and growth in lettuce in response to SL in separate seedling and head development stages. The experiment involved SL with different daily light integral (DLI) provided by light-emitting diodes (LEDs). Light treatments included supplemental DLI of 8.64, 11.52, 12.96, and 17.28 mol m-2 d-1. The results revealed that the lighting period was more effective on lettuce biomass increase than the light intensity. Although the SL increased the photosynthetic pigment content of lettuce, its impacts on the two growth stages were not the same. In a way, the chlorophyll a,
total chlorophyll, and carotenoid contents decreased under the SL conditions (DLI of 17.28 mol m2 d-1 and light intensity of 300 μmol m-2 s1 for 16 h). Increasing DLI caused a significant increase in the nutritional quality of lettuce, but antioxidant accumulation did not follow a similar trend in seedlings and mature plants. These findings confirmed that SL improves lettuce growth and quality, but optimal lighting requirements may vary depending on the growth stage.
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