Evaluation of Growth, Calcium Content, and Nitrate of Some Greenhouse Lettuce (Lactuca sativa L.) Cultivars in Response to Increasing the Night Light

An experiment was conducted as split plot based on the randomized complete blocks design, in greenhouse complex of Shahid Chamran University of Ahvaz in 2017. The main plot consisted of light treatment at two levels [a) sunlight (control), b) sunlight + red and blue LEDs (50:50%) with light intensity of 70 μmol/m2s for 15 hours (from 5 PM to 8 AM as night light] and the subplot was six greenhouse lettuce cultivars (Black Seed Simpson, Green Ice, Vivian, Tom Thumb, Red Salad Bowl and Salad Bowl). Results of the experiment showed that some of the measured traits were influenced by cultivar and light increase and some of them were under the influence of interaction effects of cultivar and light and were significant at 1% level. Maximum fresh and dry weight of leaf, fresh and dry weight of stem, number of leaves and calcium content were observed in night light treatment. Maximum and minimum values of leaf nitrate content were observed in Tom Thumb cultivar and control treatment (1723 μg/g dry weight) and Green Ice cultivar and night light (1023 μg/g dry weight), respectively. Maximum and minimum values of calcium content were observed in Black Seed Simpson cultivar and night light (1477 μg/g dry weight) and Tom Thumb control treatment (271.1 μg/g dry weight), respectively. According to the results of this experiment, by increasing the night light, it is possible to enhance the quantitive growth of the leafy lettuce cultivars by 90%, and also increase the quality of their yield