Abstract
Lettuce is one of the most suitable plant species to grow indoor or in a Plant Factory with Artificial lighting (PFAL) system, due to its short height and the relatively low light saturation point. Red lettuces are highly cultivated in PFALs, highly appreciated for its unique pigmentation and antioxidant activity, especially, the anthocyanin content that gives it the red color. However, red lettuces cultivated with PFAL in controlled environments face the challenge of having low anthocyanin content due of the lack of ultraviolet (UV) light that is necessary for its production. In this study, two red-lettuce cultivars ‘Annapolis’ and ‘Salanova’ were grown in a plant factory with LEDs (light-emitting diode) and UV light treatments to compare their growth trajectory and nutritional characteristics. Other characteristics such as Fresh Weight (FW) and total leaf area were measured to evaluate the influence of UV light in the lettuce growth. The nutritional quality of lettuces was assessed by measuring anthocyanins and polyphenols contents using a microplate reader and their ascorbic acid content measured via a reflectometer. Fresh Weight (FW), leaf area and leaf thickness under the conditions of this study, showed no effect (p>0.05) on the plants growth with the incorporation of UV radiation. However, the incorporation of UV light increased the functional components in ‘Annapolis’ and ‘Salanova’ lettuces. The polyphenol and anthocyanins contents in both lettuce cultivars showed significant differences (p<0.05). For ascorbic acid content, a significant difference was found only for ‘Annapolis’ lettuce. The incorporation of UV light can increase the functional ingredients such as polyphenols and anthocyanins without growth suppression for ‘Salanova’ cultivar. UV light increased polyphenol and anthocyanins contents in both cultivars, making them suitable cultivars for PFAL under the growth conditions used in this experiment. These results taken together can be used to improve the accumulation of functional ingredients in red lettuces without growth suppression incorporating UV light and that could be suitable for production in PFALs.
Highlights
The pineapple is one of the main export crops of Côte d'Ivoire
The internal browning of the pulp is shows more intense in the pineapple Smooth Cayenne that among the variety MD2
The application of a high amount of potassium in pineapple cultivation leads to a decrease in phenol biosynthetic enzymes which are phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL), a reduction of total phenol content in the pineapple fruits
Summary
The pineapple is one of the main export crops of Côte d'Ivoire. In the recent past, pineapple export generated more than 45 billion CFA per year to the Ivorian State and contributed 0.6% to the GDP [1]. There has been a drastic decline of the Ivorian production (213 620 tones in 1999 to 20 900 tones in 2014), followed by the loss of its status as a premier supplier of fresh pineapple on the European market The causes of this crisis are multiple, among which there was the aging of planting material, the depletion of soils due to the monoculture, the acidity of the fruit, the high rate of chemical residues, the internal browning etc. Potassium is absorbed by the plants under its ionic form K+ to regulate the osmotic pressure as well as the opening and closing of the stomata [5, 6]. This mineral is used as a cofactor in the enzymatic reactions and biochemical [5]. According to Antonio, et al [7], the application of a high amount of potassium in the pineapple inhibits the internal browning of the fruit at maturity
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